சி. எஸ். ஐ. ஆர். - கட்டமைப்பு பொறியியல் ஆராய்ச்சி நடுவம்

Spiral welding processes encounter significant challenges in the form of bubbles and hot cracking. These issues arise due to the complex nature of residual stress distribution post-welding. Residual stresses within Spirally Welded Tubes (SWTs) can lead to detrimental consequences such as fatigue cracks, stress corrosion, and compromised structural strength. As a result, an accurate and thorough assessment of residual stress distribution is essential before incorporating SWTs into structural components. The widely utilized Gas Metal Arc Welding (GMAW) method involves the use of CO2 as a shielding gas and a 0.8mm consumable solid wire as an electrode. To model the intricate residual stress distribution, advanced Finite Element Analysis (FEA) is carried out using the ABAQUS software. In order to establish a comprehensive benchmark, the distribution of residual stresses in Longitudinally Welded Tubes (LWTs) is also examined. The intricate thermomechanical behaviour of the weld is effectively captured through the implementation of the DFLUX subroutine within the ABAQUS software. Verification of the simulated residual stress distribution is accomplished using the X-ray diffraction method (XRD). This validation process encompasses both Powder XRD (PXRD) and Portable high-speed XRD (iXRD) techniques, allowing for a meticulous comparative evaluation of the outcomes. Encouragingly, a strong correlation is evident between the empirical findings and the analytical results, underscoring the robustness of the conducted study.

This study evaluates the seismic reliability of steel-concrete composite and RC-framed buildings considering vector-valued ground motion intensity measure. To efficiently predict the structural response of the structures, the appropriate choice of Intensity Measure (IM) and Damage Measure (DM) is crucial. In this study, the first modal spectral acceleration in conjunction with the measure of spectral shape is chosen as IM. The maximum inter-story drift is selected as the damage measure. The example model buildings are analyzed through Incremental Dynamic Analysis (IDA) subjected to a set of ten ground motion records. From IDA curves median curves are derived for example buildings and damage states are established from it. For the reliability analysis, a vector-valued IM is chosen, consisting of Sa(T1) and the ratio of Sa(T2) / Sa(T1), where T1 corresponds to the fundamental (first mode) time period of the structure, and T2 is selected to represent essential characteristics of the response spectrum profile. The drift hazard curves of example model buildings are developed using the reliability approach. Further, limit state probabilities are determined from drift hazard curves, and the values are compared for composite and RC-framed structures. From the reliability analysis, it is found that the composite building results in a decrease in the drift and hence increases in the reliability of the composite structure.

The compression behavior of Polyurethane (PU) foam carbon composite sandwich is studied with introducing stiffened keyway. The foam core is slotted and carbon composite layers are built with stiffened keys in single as well as two directional. Sandwich samples are prepared by co-bonded keys and tested experimentally under uniaxial compression. The load capability of bidirectional stiffened keys exhibited drastic improvement. For the same amount of height reduction during compression, the maximum load capability upto 406% is seen in bidirectional stiffened key sample as compared to the other samples. Further the improvement in load carrying capacity is seen at the tail off regime indicating the importance of key stiffening concept. Microscopic analysis is done to verify the sample of foam and the interface with keyway. Three dimensional finite element model is made and stiffened key configurations are analysed. Ogden material model with varying parameters are studied. A good correlation with finite element analysis and experimental test values are obtained.

Disposal of plastic waste is a major environmental concern. Researchers attempt to address this by reusing plastic waste. The earlier efforts made to reuse it for concrete construction have resulted in strength reduction. The present investigation attempts to reuse the plastic carry bag waste by converting them into threaded plastic fiber. The thickness of fiber is kept between 1.5 mm and 2.5 mm with a fiber length between 20 mm and 30 mm. Different percentages of plastic fiber are mixed with concrete and its influence on the strength characteristics of concrete was studied. Cube, cylinder and prism specimens are cast and experimentally investigated to arrive an optimal fiber percentage for disposing the plastic carry bag waste into concrete. The results show that the plastic fiber of up to 2% by weight of cement are not affecting the strength of concrete. Three under reinforced concrete beams with and without plastic fiber are cast and tested under two-point loading, for assessing the influence of plastic fiber in under reinforced concrete beams. From the results, it is observed that the reinforced concrete beams with plastic fiber have better performance compared to the control beam.

The steel-concrete composite structures with channel-stud shear connectors facilitate the attachment of Mero nodes by connecting the channel section and stud component. This study involves choosing the shear connector parameters and variables to analyze the steel-concrete composite space truss structure. There are a total of 54 distinct models for the parameter variables. The calibrated analytical model incorporates these factors using SolidWorks for modelling and then performs transient structural analysis with ANSYS. The research outcomes have demonstrated the influence of variables on the model using load-deflection and load-slip measurements. Modifying the channel length and thickness has significantly decreased deflection and slip in the shear connectors. However, the changes in the width and height of the channel found to be less impact on the overall performance. Artificial Neural Network (ANN) has been trained with the input and output data using the Levenberg-Marquardt backpropagation technique. For network training, testing, and validation, 70% and 30% of the analytical model results have been used, respectively. The performance of the ANN model has been assessed by data analysis and statistical methods, including Mean Squared Error (MSE) and Regression (R). The deflection and horizontal slip values predicted by the ANN model were remarkably accurate, closely matching the analytical results with a negligible margin of error.

This study aims to predict the shear behavior of Deep Beams (DB) with web openings and reinforced by struts. ABAQUS Finite Element (FE) program was used to investigate the effects of the type, dimensions, number, and position of the opening, additional reinforcement in the same direction as the strut reinforcement (AS), and Additional Vertical and Horizontal reinforcements (AVH) around the web opening on the shear behavior of the DB. The FE study results showed that the web opening had a significant effect on the shear behavior of DBs reinforced with strut reinforcement, especially for DBs with rectangular opening cuts half of the strut reinforcement. As a result of web openings cutting half or all of the strut reinforcement, the shear capacity of the DB at supports must also be taken into account. The addition of AS improved the ultimate capacity of the deep beam with a small web opening area; otherwise, it showed an insignificant effect on the varying web openings. Adding AVH around the web openings for DBs with rectangular web openings cuts half of the strut reinforcement improved the ultimate capacity and load distribution at support close to the web opening. However, the square openings that cut off all the strut reinforcements had a minor effect. Different proposed equations were provided to predict both the shear strength of the strut with the web opening and the ultimate shear strength of DB with varying web opening cut full/half of the strut reinforcement. Both struts acting as columns and the suggested equations can be used to predict the design shear strength and ultimate capacity of deep beams with web openings and reinforced with strut reinforcement, according to a comparison with the ACI318 formula and the FE result.

Grout is a dense fluid that is used to fill the gaps or used as reinforcement in existing structures. Over the last few decades, grouting technology (the use of grouts) has grown into one of the disciplines in the engineering field. The objective is to study the performance of the developed grout materials for joints of precast structural components for low cost housing with the replacement of additives or admixtures by using different industrial by-products such as Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) as eco-friendly grout materials. Generally, in grout materials, shrinkage is the major concern, and to overcome this difficulty in the developed grout mix, an expansive material, namely bentonite, is introduced. Various studies, such as, Particle size analysis, heat of hydration, compressive strength, water absorption, and shrinkage tests on the developed grout mixes were conducted. The result of this studies derives the characteristics of the developed grout mix. To substantiate the obtained results, the qualitative and quantitative analyses, such as X-ray fluorescence (XRF), thermogravimetric analysis and differential thermogravimetric analysis (TGA/DTA), and scanning electron microscopy, are also carried out to determine the behaviour of cementitious grout which has been compared with available commercial grouts.

It is very well known that the particle packing density has significant effect on the performance of concrete. There are numerous particles packing models such as Abram, Slater and ACI2000-I, Bolomey, Feret and Faury and modified Faury to address various aspects of particle packing. In the present study, the concepts of the above-mentioned models were used to derive the best proportion of fine aggregate and coarse aggregate for conventional concrete (M35 grade) and steel fiber reinforced concrete (0.5%, 1.0% and 1.5% of volume fraction). Faury’s original model has been updated to suit for any concrete mix to arrive at improved properties. The framework consists of (i) determination of targeted strength and workability by using the cement, fine and coarse aggregate, void volume, void index, w/c ratio, volume of solids required for Abram’s model, Slater model, ACI 2000-I model, Bolomey model and Feret model (ii) generation of Faury’s curve with and without cement (iii) determination of solid content (iv) verification of compaction factor considering the effect of fibers and finally (v) mix design. By using the mix design obtained through Faury’s model, compressive strength has been determined and found that the strength is higher about 10 to 18% compared to the strength obtained conventional concrete.

The damping characteristics of a healthy limb change throughout the gait cycle. However, for transtibial amputees who are wearing mechanically passive damping prostheses, the lack of ability to change the damping values might expose them to injuries and health problems during the impact of heel strike. The use of magnetorheological fluid damper in prosthetic limb, which provides a wide dynamic range, seems to be able to prevent these conditions from taking place, due to its response to the magnetic field. In this work, the vibration characteristics of a transtibial prosthetic limb with a magnetorheological (MR) fluid damper have been numerically analyzed and experimentally investigated. A simplified single-degree-of-freedom model has been developed to represent the transtibial prosthetic limb with the damper. The model is then utilized to analyze the response of the prosthetic limb along with the damper when subjected to impact, with and without semi-active control, numerically. The MR fluid damper and attachments to transtibial prosthetic limb have also been tested with impulse excitation to obtain its response with and without semi-active control. Finally, the numerical and experimental results have been compared to show the increase in efficiency of the damping of vibrations experienced during the heel strike of the gait cycle while using the semi-actively controlled magnetorheological fluid damper in the transtibial prosthetic limb.

Concrete-Filled Double Steel Tubular (CFDST) columns, a subclass of composite members, are increasingly utilized in modern construction due to their superior structural performance, including higher strength-to-weight ratio, stiffness, fire resistance, and durability compared to traditional reinforced concrete (RCC) and steel structures. While the optimization of CFDST columns has been widely studied using statistical methods like Response Surface Methodology (RSM), this study focuses on applying advanced metaheuristic algorithms for optimization. A comparative evaluation of the Algorithm (GA), Particle Swarm Optimization (PSO), and Jaya Algorithm (JA) is conducted to optimize the axial load capacity of CFDST columns by fine-tuning key design parameters. The optimization objective is to maximize axial load capacity, which serves as the fitness function in the algorithms. An empirical equation representing the axial load capacity is used as the objective function.The comparative analysis demonstrates that metaheuristic algorithms are efficient and straightforward for optimizing CFDST columns. Among the three, the JA outperforms the others, achieving faster convergence and more consistent results across various population sizes and generations. PSO also exhibits faster convergence than GA, though JA remains the most robust and reliable. The study observes that the axial load capacity of the columns increases by 4.17%, 13.9%, 1.16%, and 10.81% for the considered series of specimens utilizing the same or fewer geometric values of key design components. These findings highlight the potential of metaheuristic algorithms in enhancing the design efficiency of CFDST columns for modern structural applications.

Buildings with single or multiple irregularities are highly vulnerable to seismic events. However, there are large number of existing buildings and new constructions with multiple irregularities both in the urban as well as rural areas of developing countries. Earlier earthquake events have demonstrated the failure patterns of the irregular reinforced concrete buildings. In the literature, only few experimental investigations have been reported on the reinforced concrete buildings with multiple irregularities. Hence an experimental investigation is carried out to study the seismic behaviour of reinforced concrete buildings with vertical and plan irregularity by conducting shake table test. The dynamic characteristics of the model building are evaluated. Based on the experimental results, the seismic behaviour of the building with multiple irregularities is studied and the code provisions as per IS1893 on the above irregularities are reviewed. The half-scale model reinforced concrete building is subjected to increasing magnitude of seismic input IS 1893 soft soil earthquake spectrum and the dynamic responses of strain, acceleration, and displacements are analysed and discussed along with the failure modes of the building frame with plan and vertical irregularity in this paper.

This study investigates the thermal performance of Sandwich Wall Panels (SWP) incorporating bamboo as the core insulating material. The SWP specimens were made from solid sintered fly ash aggregate concrete with bamboo arranged in various configurations, including full culm, half culm, and checkered culm patterns, alongside a control specimen. Eight specimens were tested to evaluate heat transfer and the rate of heat flow through the different bamboo arrangements, assessing their insulating effectiveness. A custom-designed hot box and heat control system, calibrated with materials of known thermal conductivity (expanded polystyrene, plywood, and newspaper), were used for thermal analysis. Temperature data were monitored in real-time using a Programmable Logic Controller (PLC) and Supervisory Control and Data Acquisition (SCADA) system. The thermal resistance of each pattern was calculated and compared with finite element analysis results from ANSYS, showing a high correlation with an error margin of just 0.5%.

This study introduces a novel construction material, pumice-based Lightweight Pervious Concrete (LPC), which combines the benefits of lightweight aggregates, high porosity, and sustainability. Pumice, a naturally occurring volcanic rock, offers low density, high porosity, and pozzolanic properties that enhance the performance of pervious concrete. The study explores the mechanical, hydraulic, and durability characteristics of LPC by analyzing its density, void ratio, permeability, and microstructure. Various mix designs for pervious concrete were tested, categorizing them into two groups: conventional coarse aggregate and pumice. Wet density values for lightweight mixes (LW) ranged from 1440–1480 kg/m3, with dry densities from 1410–1465 kg/m3, significantly lower than Conventional Concrete (CC) mixes, which had wet densities of 2110–2190 kg/m³ and dry densities of 2090–2170 kg/m³. The void content in LW mixes was 22.2–23.87%, higher than the 19.21–19.87% of CC mixes, promoting permeability and groundwater recharge. Permeability tests demonstrated superior infiltration rates in LW mixes, with values up to 20.12 × 103 mm/hr, highlighting their efficacy in stormwater management. Despite lower compressive strength (2.47-5.99 MPa), LPC exhibited satisfactory performance in lightweight applications. Microstructural analysis revealed pumice’s rough, porous texture, enhancing the C-S-H gel bond while contributing to higher porosity.

This study investigates the effects of Steel Fibers (SF) and Recycled fine Aggregate (RA) from Construction and Demolition waste (CDW) on the mechanical and fracture properties of Steel Fiber-Reinforced Geopolymer Mortar (SFRGM). SF was incorporated at varying volume fractions (0%-1.25%), while natural sand was replaced with RA at levels of 0%, 10%, 20%, and 30%. The study examines compressive strength, splitting tensile strength, and flexural strength, as well as fracture characteristics such as load-deflection behavior, peak load, and fracture energy using three-point bending tests on notched beams. Results show that up to 20% RA replacement caused moderate reductions in compressive, tensile, and flexural strengths, with more pronounced decreases at 30% RA. The inclusion of SF notably improved strength parameters by 20%, 45%, and 80%, respectively, while enhancing ductility and energy absorption. Although RA slightly lowered fracture energy, SF significantly increased it, with a 1% SF content yielding approximately 59 times the fracture energy of the control sample across all mixes. These findings suggest that integrating RA and SF in SFRGM offers a potential alternative to conventional cement-based materials.

The current paper is focused on the potential usage of sea sand in concrete. Sea sand was collected from two different sources, namely Puri sea shore Odisha, and Digha sea shore, West Bengal, India. Mechanical properties and resistance to chloride penetration of concrete comprising various combinations of natural river and sea sand, ranging from partial substitution in washed and unwashed conditions to 100% replacement with sea sand, were evaluated. The study revealed that, sea sand concrete gains early strength faster whereas the rate of gain in strength decreases with time. The 7 days strength of Puri beach unwashed sea sand is 46.52% higher whereas after 28 days of curing, attains about 22.74% lower strength than Reference Concrete (RC). On the other hand, though it gains less strength initially, concrete with washed sea sand from Puri reaches similar strength with RC at 28 days. The result differs with the percentage replacement for Digha beach sand. Rapid Chloride Penetration Test (RCPT) results indicated that the total charge that passes through the sea sand concrete decreases with age and the chloride resistance was not significantly impacted by the chloride ions from sea sand, at later stage.

Among the various failure behaviours of castellated beam (CSB), the buckling failure of web post is more critical because of increased web depth. The two prominent buckling failure modes of the castellated beam are Lateral Torsional Buckling (LTB) and Lateral Distortional Buckling (LDB) of web. Numerous studies regarding buckling behaviour of CSBs with commonly used hexagonal and circular openings have already been reported in the literature. In this paper, parametric study on CSBs with sinusoidal openings is carried out to investigate lateral torsional and distortional buckling of the web. Four CSBs are fabricated by varying the ratios of spacing between openings to opening depth (S/Do) and the overall depth to opening depth (D/Do) which are then experimentally tested under one-point loading. These CSBs are also analysed by using finite element-based ABAQUS software. After validating the numerical model of CSBs for load-carrying capacity and deflections with experimental results, the parametric study on 20 CSBs with varying S/Do and D/Do ratios is carried out to investigate the effect on failure load and failure modes. The investigation shows that a change in the S/Do ratio has negligible effect on failure load of LTB of CSBs whereas LDB failure load increases with an increase in the S/Do ratio. However, the failure load for LTB mode decreases with an increase in the D/Do ratio whereas failure load for LDB mode increases with an increase in the D/Do ratio. The study also shows that Finite element analysis can be satisfactorily used for the prediction of failure load and failure modes of CSBs.

In the realm of micro electromechanical systems, comprehending their behaviour is paramount importance for practical applications. Analysis of these structures often involves grappling with size effects, rendering traditional methods like finite element analysis complex. To confront this challenge head-on, this study endeavors to develop a micro-plate model by integrating the modified couple stress theory, thereby capturing size effects inherent in electro-mechanical systems. The primary focus lies in probing critical loads and resonant frequencies of micro-plates through a meticulous parametric and comparative inquiry. This investigation encompasses an examination of the influence of length scale parameters, material gradient in- dices, and aspect ratios as prescribed by the modified couple stress theory. To surmount the constraints of conventional techniques, we establish a comprehensive database encompassing diverse geometric and material properties, alongside an array of boundary conditions. This rich dataset amalgamates results derived from the analysis of microplates utilizing methodologies like the Differential Quadrature or Finite Element Method (DRM or FEM), in addition to findings from other researchers. Moreover, this paper pioneers the integration of Deep Learning Neural Networks (DLNN) and Support Vector Machines (SVM) to predict critical loads and natural frequencies for any microplate within the specified parameters. The SVM lever- ages hyperplanes and Kernel functions for data classification and regression, while the DLNN, with its intricate network architecture, minimizes errors through forward and backward propagation. The trained models exhibit remarkable adaptability across various problem types, representing a significant stride in applying Artificial Intelligence (AI) methodologies to delve into the stability and dynamics of microplates.

This paper investigates the stability of Greenhill’s shafts subjected to non-conservative torques and fixed axial compressive load using. Variational Iteration Method (VIM). The effectiveness of VIM in solving a differential equation primarily depends on the Lagrangian multiplier used in the recurrence formula for iterations. In this paper, exact Lagrangian multipliers are proposed for the first time to solve the governing differential equations of Greenhill’s shafts using VIM. Using these exact multipliers, the divergence and flutter loads of Greenhill’s shafts are determined. The interaction between conservative fixed loads and the non-conservative axial moments are also studied. Comparisons are drawn between the convergence of the numerical results obtained using the proposed exact Lagrangian multipliers and the approximate Lagrangian multipliers. The paper also focusses on the Nicolai’s variant of a Greenhill’s cantilever shaft subjected to axial torque. Parametric studies are conducted using VIM to study the effect of damping and imperfections on the behavior of Nicolai’s shaft. The results obtained from VIM are used to create stability maps of shafts subjected to tangential torque for different levels of damping.

The detection and quantification of cracks in historical monuments are necessary to preserve and protect them from severe damage. Hence, this work proposes a methodology to detect the defects in historical stone monuments, classify them as granite stone defects, sandstone defects, and defective joints, and measure their length and width. Standard mask Region - Based Convolutional Neural network (R-CNN) fails to detect small defects or objects accurately and cannot predict accurate masks under specific defect detection applications. Hence, an automatic crack identification, localization, and classification technique using Improved Crack Detection (ICD) mask R-CNN is proposed in this work to improve the mask accuracy and enable the system to detect smaller cracks too. This is achieved by providing spatial resolution details directly from the feature pyramid network to the mask predictor and using DICE loss in the mask head. The size calculator algorithm is used to calculate the length and width of the detected defects. The Root Mean Square Error (RMSE) between the actual and predicted mask is calculated for the length and width of the crack. For the cracks under consideration, ICD mask R-CNN has achieved an increase of 11.8% in detection accuracy on average, compared to the standard mask R-CNN. Moreover, ICD mask R-CNN has also achieved better detection accuracy compared to the deep crack and YOLO-v3 algorithms.

State-of-art performance based requirement of seismic design of building requires that for life safety, probability of collapse in 50 years should not exceed 1%. In this paper, a methodology for estimation of mean annual rate of exceedance of collapse of buildings is demonstrated for two buildings B1 and B2. For B1 which is a three storey steel building frame two hazard risk levels (2% and 0.1% probability of exceedance in 50 years) and one site location (Bhuj) are considered. For B2, four different locations (Ahmedabad, Chennai, Mumbai and Banglore) and one seismic hazard risk level (2% probability of exceedance in 50 years) are considered. From the study, probability of collapse of B1 in 50 years for Bhuj site for an earthquake hazard risk of 2% probability of exceedance in 50 years is estimated to be 75%. Probability of collapse of B2 in 50 years for Ahmedabad, Chennai, Mumbai and Banglore are estimated to be 6.83%, 0.056%, 4.78% and 0.012% respectively. Further, this methodology brings out the spectral acceleration Sa(T1) which contributes maximum to the hazard which is also a useful design parameter. Methodology demonstrated in this paper is useful for estimation of probability of collapse of building for a given design life of structure.

To develop earthquake-resistant structures, substantial research and the dissemination of design and detailing knowledge are essential for structural elements. The current study involves both numerical and experimental investigations focused on the behavior of external slab-column connections under cyclic loads. Three distinct specimen types were assessed: a Conventional Specimen without shear reinforcement in slab (CS), a specimen featuring shear stud reinforcements arranged in a radial pattern, with forging slag and Styrene Butadiene Rubber (SBR)-modified concrete at the joint (SSR), and with a specimen with steel fiber-reinforced concrete at the joint (SSC) and shear studs. These scaled models (1/4th scale) underwent axial loading applied at the top of the column stub, and cyclic loading to the slab edge. In all axial and cyclic stress scenarios, the models with Slab Shear Reinforcements (SSR and SSC) showed superior resistance to punching shear failure under both axial and cyclic loading conditions. The inclusion of shear stud reinforcements (SSR and SSC) notably enhanced the ductility compared to the CS. Furthermore, the energy dissipation capacity of the specimens was evaluated and compared, with shear reinforcements showing a significant improvement.

Past earthquakes have shown that selective pallet racks are susceptible to to pallet shedding and collapse along the cross-aisle direction. Seismic base isolation, a well-established and proven technology in buildings and bridges, is not widely adopted for steel pallet racks. The primary challenge lies in the wide range of pallet weights and unpredictable stacking patterns, making it difficult to design a base isolation system suitable for all load conditions. This is where XYFP isolators offer a significant advantage. During seismic action, these isolators generate a fundamental natural period independent of the weight placed on them. Additionally, these isolators feature a built-in uplift-restraining mechanism to prevent rack overturning during seismic action. The paper investigates the seismic behaviour of a selective pallet rack equipped with XY-FP isolators at their base. The parametric study explores numerous combinations of the isolator’s friction coefficient and radius of curvature, the pallet weight on the rack, and the diaphragm’s rigidity. Each baseisolated model is subjected to three sets of ground motions: far-field, near-field with PGV/PGA<0.2, and near-field with PGV/PGA>0.2. A nonlinear finite element analysis that accounts for the nonlinearity of the isolator and the geometric nonlinearity is employed. This research proposes ideal combinations of radius of curvature and friction coefficients for XY-FP isolators. By optimizing these parameters, peak shelf-level acceleration and isolator displacement can be kept within safe limits, effectively preventing pallet sliding and mitigating earthquake-induced damage. For far-field ground motions, most base-isolated configurations with friction coefficients of 0.11 and 0.14 at high sliding velocities (μmax) perform adequately. In near-field conditions with PGV/PGA< 0.2, only two configurations - μmax of 0.14 with natural time periods of 2.5s or 3.0s - meet the performance criteria. However, for near-field ground motions with PGV/PGA>0.2, there is no configuration that effectively constrains critical response parameters within reasonable bounds.

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The present study examines the effect of Alkali Activator Solution (AAS) on the consistency and setting properties of the blended binder geopolymer pastes considering the following parameters: (i) geopolymer pastes produced with three different alkali activator ratios (sodium hydroxide: sodium silicate) 1:1, 1:2 and 1:3, (ii) geopolymer pastes produced considering four different molarities of Sodium Hydroxide Solutions (SHS) 2.5M, 5M, 7.5M, and 10M, and (iii) geopolymer pastes produced as blended geopolymer pastes with varying blending ratios of FA and GGBS 30:70, 50:50 and 70:30. The consistency and setting characteristics of geopolymer pastes for the 36 different mix combinations were studied. The finding revealed that the molarity of SHS and the ratio of AAS are influencing the consistency and setting characteristics of the proportionately blended FA and GGBS-based geopolymer paste. The increase in the AAS ratio has minimal effect on the consistency of geopolymer pastes except for the geopolymer paste produced with 10M of SHS. The initial and final setting times of geopolymer paste decrease with an increase in the ratio of AAS. The flash setting of geopolymer paste was observed for mixes J3, K3, and L3 which are produced with 10M of SHS and an AAS ratio of 1:3. Microstructural studies such as Scanning Electron Microscopy (SEM) analysis and Fourier Transform Infra-Red Spectroscopy (FT-IR) analysis were carried out. The formation of ettringite was seen in SEM images of FArich mixes of geopolymer paste activated with 2.5M molarity of NaOH.

The Imperial Smelting Furnace Slag (ISF Slag) is a byproduct of zinc mining. The ISF slag contains hazardous elements such as lead and zinc and a thorough treatment before its disposal is required which demands a significant investment of time, money and effort. Also, increased construction activities produce large amounts of Waste Marble Powder (WMPs) and Construction and Demolition (C&D) waste which results in severe environmental degradation. The first goal of this paper is to propose a pathway for the safe disposal of these wastes by partially substituting them in concrete in place of Fine and Coarse Aggregate (FA & CA). Secondly, this research aims at to identify an optimal combination of these wastes for improved strength and environmental benefits. The results of experimental study shows that a combination of, a) 10% WMPS and 15% ISF slag, b) CA replaced by 10% C&D waste in concrete with addition of 1% Hooked Steel Fibers (HSF) (by weight of cement) exhibits best strength enhancement of 13.26%, 16.52%, and 18.43% in compression, tension, and flexure respectively. The environmental impact assessment using Recipe mid-point and end-point analysis shows reduction of particulate and greenhouse gas emission by 35.5% and 41.8%, respectively.

Two-way slabs are commonly used in Reinforced Concrete (RC) structures to resist gravity and lateral forces. Walls or RC beams and columns typically support these slabs. When designing slabs using the limit state method, strength and serviceability criteria must be met. Even though current codes have established design methods for strength limit states, they lack well-established design methods for serviceability limit states, particularly crack width calculations in two-way slabs. Although a few studies from the literature have examined the cracking behaviour of RC two-way slabs in scaled specimens, those that investigate RC two-way slabs supported on beams have not yet been reported. This paper delves into the complete cracking behaviour of two-way slabs using an experimental investigation on four prototype RC two-way slab systems supported on beams, with varying slab thicknesses and reinforcement spacing. The study demonstrates that the cracking behaviour of RC elements under two-way bending differs significantly from that under one-way bending. The current research thus reveals the need for the development of a different analytical expression for crack width estimation in two-way slab systems. The findings of this research work could be valuable as an input parameter in developing code provisions for crack width calculation in two-way slabs.

This paper presents experimental investigations on the behaviour of steel columns under elevated temperature. Axial restraints were applied to simulate the real-time boundary conditions, being part of a steel-framed structure. In the present study, two specimens, namely ISMB200-H1 and ISMB200-H2 were exposed to elevated temperature conditions by using 24kW and 7kW heaters respectively. The heating was carried out from room temperature to 800°C gradually, under a constant axial load applied through a specially fabricated loading frame. The critical temperature was estimated based on the point at which the specimen could no longer withstand the applied load. The applied load was significantly influenced by axial restraint, wherein additional stress was generated due to restrained thermal elongation in the axial direction. Two types of failures were observed at the end of experiments, namely (i) local mode of failure in the specimen ISMB200-H1 and (ii) global mode of failure in specimen ISMB200-H2 due to temperature concentration (maximum temperature) at top end plate and mid-height of the specimens respectively. The analytical studies were carried out with the expressions available in BS EN 1993-1-2, IS800:2007 and CSA S16:19 to have an understanding on load carrying capacity with increase in temperature. It is inferred that analytical studies provided comparable results on the load-bearing capacity of the specimen ISMB200-H2, which has failed by global mode.

Worldwide, industrial constructions are frequently built using light gauge materials like Cold-Formed Steel (CFS) sections due to its lightweight and affordable design systems. One important aspect of building design and construction that must be considered is fire safety. The research involved studying flexural and web-crippling behaviour of CFS built-up beams subjected to controlled high-temperature conditions, then it was cooled to room temperature by furnace cooling method. Ten back-to-back built-up CFS sections were prepared to check structural performance after exposure to elevated temperatures of 500oC, 600oC and 700oC in an electrical furnace. The Finite Element (FE) modelling results are validated by experimental results. The validated FE models were then employed to carry out a comprehensive parametric study to investigate the effects of different web-to-thickness ratios, as well as sectional size to thickness ratio. The results demonstrated that the load carrying capacity and bending moment for flexural behaviour and web-bearing capacity for web-crippling behaviour of the CFS members can be significantly affected, (up to 56.04% and 37.26%, respectively with reference temperature) after exposure to elevated temperature. From the study, it is concluded optimizing the web height to thickness ratio is crucial for enhancing the structural performance of CFS components. However, higher temperatures resulted in a greater reduction in the load carrying capacity of the specimens.

Geopolymer concrete has emerged as a viable alternative to Portland cement concrete in recent years. Binders in geopolymer concrete are distinctively different from those in Portland cement concrete. The variation in properties of a geopolymer matrix can be high since the raw materials used are industrial wastes with essentially no control over their composition. This necessitates a complete characterization of the material as well as a thorough study of its mechanical, durability and structural properties. In this study, the flexural performance of reinforced geopolymer concrete beams designed as per Indian standards has been experimentally studied. The results though vindicate the use of geopolymer concrete in structural members, it has revealed that the structural behaviour of reinforced geopolymer concrete can distinctively differ from that of reinforced concrete beams made with Portland cement concrete. Results reported here indicate a reduced ductility in reinforced geopolymer concrete beams. Revision in the provisions of current concrete codes may be necessary. Relation between the properties of geopolymer concrete and the raw materials used in them needs to be thoroughly documented.

Concrete Filled Double Steel Tube (CFDST) columns are composite columns consisting of concrete sandwiched between outer and inner steel tubes with a central hollow portion. CFDST members can be used in marine structures, bridges, high-rise viaduct piers, composite piles in offshore structures and high-rise buildings, due to their strength and stability. The performance of these composite structures is greatly affected by the corrosion of steel tubes. The present study aims at experimental and numerical investigations on the corrosion behaviour of Mild Steel - (MS)-CFDST column and Epoxy coated Galvonized Iron (GI)-CFDST columns. It also aims at to investigate numerically the fatigue behaviour of CFDST column under reversed cyclic loading using validated finite element model. A total of 6 specimens, three no. of MS-CFDST and epoxy coated GI-CFDST each were cast, and immersion corrosion testing was conducted for a time period of 60 days. The corrosion rate and failure pattern of the CFDST columns were determined. The fatigue strength of corroded CFDST columns were also evaluated by finite element modelling.

Most of civil structures deteriorate with time due to many factors such as ageing, repeated loadings, wear-and-tear, lack of maintenance, and other environmental influences. While the structures are designed for strength, stability and deformation, the issues that are common are those of deterioration, durability and serviceability. Therefore, it is essential to assess the condition of the structures periodically if not continuously to prevent the deterioration leading to the decline of the strength, stability/serviceability. In real practice, the condition of structures is evaluated through condition assessment procedures. To evaluate the deterioration due to loss of stiffness, acceleration measurement which reflects the global information, is a great option when compared to strain, which needs a greater number of strain gages to capture the local information of a structure. In this paper, a method to evaluate the condition of a structure using acceleration responses is presented. The proposed technique is illustrated through an example of a steel building subjected to ambient excitations due to the operation of machinery. The technique is based on the updating of the Finite Element (FE) model of the structure, using the frequencies obtained from the measured acceleration response from the field. The frequencies obtained from the Modal analysis of the FE model are compared with the frequencies obtained from the field measurement. The dominant frequencies, excited with higher amplitudes in the field are found to be nearer to the FE frequencies but not the same. One of the main reasons for the difference is the change in the actual stiffness due to the deterioration of the member. This change or loss of stiffness is captured by updating the model with the frequencies of the field measured signal. Once the loss of stiffness is assessed, the current load-carrying capacity corresponding to the updated model is evaluated. The results of the studies from the steel building indicate the feasibility of the vibration-based technique for condition assessment. The proposed technique is able to identify the stiffness loss due to a reduction of the thickness of the column members by 9%, which is also verified using an ultrasonic thickness gauge in the field.

Indirect Structural Health Monitoring (SHM) otherwise known as vehicle-scanning method for bridge health monitoring is increasingly gaining importance due to the advantages such as the usage of single sensor on the moving vehicle without installing any sensors on the bridge, operation of traffic during vehicle-scanning, and better spatial resolution of the bridge due to moving sensor. The extraction of bridge frequencies, mode shapes, and damage using the drive-by method are posing few challenges due to the presence of roughness, measurement noise, and less transmissibility of the bridge characteristics. In order to obtain the bridge parameters and damage features, powerful signal processing tools are being relied on. One of the effective ways to perform feature extraction is through the decomposition of the signal into useful components. In this paper, three signal decomposition techniques namely, Variational Mode Decomposition (VMD), Empirical Fourier Decomposition (EFD), and Singular Spectrum Analysis (SSA) which are robust in handling mode mixing and measurement noise are employed for extraction of bridge frequencies using the vehicle response. The performances of the three decomposition techniques are compared to evaluate their efficiencies for indirect SHM of bridges, using the drive-by vehicle. The comparative analysis is made and findings are obtained using the numerical simulation of a simply supported beam, with moving vehicle under varied speeds, road roughness, and measurement noise. The results of the numerical investigation show that the three techniques are efficient in decomposing the signal without mode mixing. It was found that, while the speed of the vehicle has no effect on the performance, measurement noise and roughness are affecting the effectiveness of the techniques. Also, SSA was found to outperform the other techniques in extracting the maximum number of mode shapes when compared to the other decomposition techniques from a noisy signal.

At first, Hybrid Steel Fibre Reinforced Concrete (HSFRC) mixtures are developed and characterized for developing HSFRC overlay strips for flexural strengthening of Reinforced Concrete (RC) beams. HSFRC is developed using cement, sand and coarse aggregates of size 10 mm down, short straight-and long hooked-ended steel fibres in 1:3 proportion and densified silica fume to replace 7% by weight of cement. The fibre content is varied as 0.5, 1, 1.5 and 2% volume fraction. In order to assess the suitability of the HSFRC mixture developed for retrofit application, the mechanical and fracture characteristics of HSFRC are compared with that of plain concrete of same mixture proportion without fibres. Based on the merits, HSFRC with 1.5% volume fraction of fibres is chosen for the development of HSFRC overlay strips. The performance of a reinforced concrete beam after flexural strengthening with an innovative reinforced HSFRC overlay strip is compared with that of an unstrengthened control beam. Numerical model of RC beam retrofitted with reinforced HSFRC strip is developed and validated by comparing the results of numerical study with experimental results. A parametric study is carried out to evaluate the influence of thickness of overlay strip, level and strength of overlay reinforcement on the load carrying capacity and stiffness of the retrofitted beam. The v parametric study brings out the potential of reinforced HSFRC overlay in flexural strengthening of RC beams and its ability to emerge as economic, feasible and promising retrofit strategy.

This paper presents investigation in alkali activated paste and alkali activated mortar produced by combinations of fly ash collected from coal based thermal power plant and ground granulated blast furnace slag collected from steel manufacturing facilities. The fly ash and ground granulated blast furnace slag are industrial by-products rich in aluminosilicates. The present study focuses on effect of utilization of seawater-based alkaline activator solution in alkali activated paste and mortar. Alkaline activator solution activates the chemical processes in binder materials when used in right concentrations and right proportion. This paper discusses the mechanical properties and microstructure characteristics of seawater-based alkali activated paste and mortar in comparison with conventional distilled waterbased alkali activator. The usage of sea water shown insignificant change in setting times and compressive strengths for various combinations of binder material. The microstructure analysis also showed less variation in mineralogical formations when conventional distilled water is replaced with sea water in preparation of alkaline activator solution.

Applied Element Method (AEM) is a numerical method which conventionally uses rectangular elements for structural analysis. AEM is advantageous because of its simplicity and faster processing. AEM can be used to track the collapse of structures. This method deploys the conversion of the structure into an assembly of rigid elements and flexible springs. Basically AEM has only two elements – two dimensional element and three dimensional (3D) element. Generally, 3D element is used for the analysis of 3D curved members which consumes more memory and processing time. For this, a shell element is necessary to represent the curved nature of the structure. This paper attempts to develop a singly curved shell element for AEM. The analysis of axisymmetric member illustrates the use of shell element. The effect of Poisson’s ratio normally neglected in rigid body methods is incorporated in this simplified shell element. The element developed is validated by both static and modal analyses. The results show that AEM is effective in predicting the behaviour of singly curved structures accurately.

Phase Field (PF) theory is based on the variational principle and emerges as an efficient mathematical tool for numerical simulation of fracture behavior. The crack initiation and propagation solution within a unified mathematical model presents an added benefit to PF theory. PF formulation introduces two additional parameters: (1) phase field variable (f) that discriminates the cracked and uncracked surface and (2) length scale parameter (L) converting the sharp crack into a diffusive crack. This paper investigates a comparison study of 2D and 3D Finite Element (FE) analysis results using PF concept w.r.t ductile fracture. The mathematical formulation for the phase field method considering plasticity is carried out using AT1 and AT2 model. Numerical FE modelling is performed using ABAQUS software by considering quadrilateral element for 2D and hexahedral element for 3D simulations. Three standard benchmark examples were discussed in detail, and numerically predicted load-displacement results were compared with the results available in the literature. Further, the effect of L on crack behavior and loading capacity of the specimen is studied. The primary observation from the study states that an increase in the value of L, decreases the load carrying capacity and plastic dissipation of the material.

Pile caps are deep members provided under the column to safely transmit the loads to the piles beneath. These members can be classified as disturbed regions, due to their low shear span-to-depth (a/d) ratios and traditional sectional methods of design are not valid. These members are popularly designed using the strut-and-tie method. The Indian standards do not have recommendations for strut-and-tie based design and designers usually adopt the sectional method of design considering flexure, shear (one-way and punching), and bearing strengths. The study attempts to compare the strength estimation of pile caps using sectional method in IS 456 and the strut-and-tie method as in ACI 318. The strut-and-tie method predicted about 1.8 times more strength than sectional method for pile caps with shear span-to-depth (a/d) ratios less than 0.9. For a/d > 1.0, the difference in strength prediction is not very significant. Previous studies have shown that the sectional method can lead to unsafe design. Hence, the study strongly recommends strut-and-tie method of design especially for deep pile caps with a/d

For decades, the shear carrying capacity of Reinforced Concrete (RC) members has been studied both experimentally and analytically by researchers worldwide. Despite all the efforts by the researchers, the shear resistance mechanisms of RC members remain a complicated and debated phenomenon. As a result, different codes around the world have their shear design provisions based on different experimental and theoretical grounds. The study is categorized into two parts. First, the adequacy of the one-way shear design method of Indian Standard (IS)-456 in predicting the shear strength of RC members without and with stirrups is assessed, and second, the safety level associated with the existing one-way shear design method is examined. The uncertainty associated with the material properties, fabrication factor, and analysis method is considered in this study. The reliability analysis is performed for a combination of dead and imposed load values. The findings of this study exemplify the need for a new shear design method that offers a more uniform level of conservativism for all the factors influencing shear strength, as well as reliability analysis-based calibration for shear strength design with a higher level of uniformity in terms of safety and efficiency.

Two significant problems that require immediate attention are (i) the rising demand for building materials to meet the expanding demands of the construction industries, and (ii) the rising production of industrial wastes that must be properly disposed of as a result of rapid industrialization and growing urbanization. Therefore, researchers have been working continuously to find solutions to these issues and have been investigating the potential uses of industrial waste slags as an alternative, sustainable construction material. Given that the slags can vary in their chemical compositions and may contain large concentrations of heavy metals, rendering them toxic and dramatically modifying their properties, a comprehensive study of the slag attributes is crucial in this context. As a substitute for river sand as fine aggregate in reinforced cement concrete, copper slag, a byproduct of copper smelting and refining, is discussed in detail here in terms of its structural, mechanical, physical, and chemical qualities. In order to determine the electronic structure, surface atomic concentrations, and phase analysis of the slag concrete, X-ray photoemission spectroscopy analysis, powder X-ray diffraction measurements, direct shear analysis, ultrasonic pulse velocity analysis, and rapid chloride permeability tests were conducted.

It is known that damage tolerant evaluation has primarily two objectives, namely, crack growth life and residual strength. In the present study, remaining life and residual strength evaluation of SA 333 Gr. 6 carbon steel straight pipes with circumferential part through crack under cyclic loading has been carried out. The study involves evaluation of accurate crack driving force, i.e., Stress Intensity Factor (SIF), crack growth and remaining life of cracked pipe. SIF has been evaluated for the cracked pipes using French RCC-MR and R6 approaches. Crack growth life has been evaluated using Paris law. The predicted crack growth life has been compared with the previous experimental results and found to be close to each other with maximum difference of 13%. Residual strength has been determined by using (i) plastic collapse condition with yield stress and flow stress (ii) fracture toughness criterion and (iii) remaining life approach. The residual strength obtained using plastic collapse condition with yield stress is lower compared to other approaches. The predicted remaining life and residual strength are useful for safe operation of power plant structures based on fitness for purpose requirements.

Glass Fibre Reinforced Gypsum (GFRG) panels can be used as infills in multi-storeyed framed construction, and the lateral load behaviour of GFRG infilled Reinforced Concrete (RC) frames is strongly influenced by the filling inside the cavities of the panel. When the cavities of the panel are left unfilled, the connection between the GFRG panel and the RC frame is established using Cold-Formed Steel (CFS) sections with suitable screw connections. A quasi-static cyclic lateral load test was performed on GFRG infilled RC frame with empty cavities to understand their behaviour. The results highlighted the significance of the screw connection between the GFRG panel and CFS plate, which experiences shear, in determining the behaviour of GFRG infilled RC frames. Therefore, the behaviour and strength of the screw connection between CFS profiles and the GFRG panel was studied by conducting monotonic and cyclic shear load tests. The results demonstrated the influence of CFS plate thickness, screw diameter, edge distance of the screws and placement of the CFS plate on various performance parameters of CFS-GFRG screw connection.

Superior high-performance steel is an advanced type of steel. Columns are the critical members of a structure. Columns subjected to fire may fail due to overall buckling, flange buckling, or member instability. This study concentrates on the overall buckling failure of superior high-performance steel columns under axial compression subjected to fire. The critical temperature and amount of axial elongation of columns when subjected to fire were analysed in detail. The critical temperature and axial elongation of columns are affected by their geometrical parameters. The present study carried out a numerical investigation using finite element software ANSYS®. The existing experimental results in the literature were used to develop the numerical models, which were validated against the results obtained from experiments. After successful validation, a detailed parametric study was conducted. Mainly six sets of parameters were considered in this study, which are related to flange slenderness ratio, web slenderness ratio, size of perforations, spacing of perforations, spacing of stiffeners, and cross-sectional shape. The influence of axial load ratio on the effect of geometric parameters was also studied. The specimen showed an 11°C increase in critical temperature without affecting the pre-failure behaviour when the web depth to web thickness ratio was increased from 3 to 9. The increase in flange width to flange thickness ratio from 3 to 9 under an axial load ratio of 0.7 increased the axial elongation by about 10 mm in addition to a 20% increase in the critical temperature. Columns with closely spaced and larger perforations failed at an early temperature without affecting the amount of axial elongation.

The control of the dynamics of oscillatory movements with the help of active (reactive) dampers is considered. The principle of operation of a reactive damper is to create an alternating reactive force that prevents relative (bending) movements (oscillatory movements) of the structure at the right moments of time. It is shown that the process of activating the reactive damper from seismic impact on the structure is carried out by the triad “displacement – speed– electric drive of the damper”. Graphs of the dependence of the damper operation depending on the change of individual parameters of the damper - the velocity of the jet Vgas, the duration of the jet Tgas, the maximum permissible relative deviation δmax. The analysis of the influence of these parameters on the efficiency of the damper is carried out. It is shown that a reactive damper with rationally selected parameters allows to reduce the level of mechanical vibrations of buildings and structures in conditions of non-stationary (seismic) impacts by 50-80%. A software tool has been developed that allows choosing the optimal parameters of a reactive vibration damper for this structure

This paper presents a numerical approach to evaluate the ultimate load and the flexural behavior of the two-way sphere voided slab-beam systems with various layouts of sphere voids. The slab is the most widely used structural element, used in framed and regular load-bearing masonry constructions. A voided slab is a reinforced concrete slab in which void shapers are placed between the top and bottom reinforcing bars before the concrete is poured to reduce the slab’s self-weight. The developed model was validated with prior experimental work available in the literature. The reinforced concrete model was created using nonlinear stress-strain relationships of concrete and reinforcing steel. The flexural capacity of the sphere voided slab-beam was determined in the numerical model, and later its structural parameters were compared with the control model. Numerical results indicate that the change in the load taken by the sphere voided slab-beam model is 12.6% more than that of the control model. It is because of the 10% reduction in the self-weight of the sphere voided model than the control model. A parametric analysis was conducted to study the impacts of spherical balls with various configurations on flexural capacity. The slab-beam model’s lowest ultimate load is observed in the three rows of sphere voids provided in only one direction case (X-3 row SV model). The slab-beam model has the highest flexural load in the three rows of sphere voids provided in both directions case (X and Y-3 row SV model). The deflection contour of the X and Y-3 row SV model differs from the X-3 row SV model. At 100 mm deflection in the slab, the beam deflection of the X-3 row SV model is 11.27 mm, while the beam deflection of the X and Y-3 row model is 17.88 mm. The arrangement of voids inside the slab influences flexural parameters like initial cracking load, rebar stress and deflection contour.

In this study, free vibration characteristics of a three layered magnetorheological fluid embedded viscoelastic cored sandwich beam have been investigated using numerical and experimental approaches. The numerical approach involves finite element method incorporating layerwise modelling considering Euler – Bernoulli’s theory for top and bottom aluminium sheets. The axial displacement field for the central core is linearly interpolated in terms of the corresponding displacements of the face sheets. The transverse displacement field is assumed to be same for all the layers. Natural frequencies of the beam in cantilever configuration have been determined using numerical and experimental approaches for different strengths of magnetic fields exposed to the magnetorheological fluid. The results obtained from both the approaches agree closely with each other and illustrate the effect of introducing magnetorheological fluid in the sandwich beam.

Machine Learning (ML) approach is one of the finest methods in Structural Health Monitoring (SHM). Its capacity in handling huge data and accuracy in predictions has made it a powerful tool in SHM. The data from the sensors monitoring the structure is used for damage detection and identifying the sources of disturbances in the structural system. This study examines the algorithms of machine learning for categorising the various structural states in a three-dimensional frame. Three structural states are taken in the present study for the dynamic analysis: the normal case (UD), the added mass case 1 (DC1), where an extra mass is added at level 1 of the frame, and the added mass case 2 (DC2), where an extra mass is added at level 2. Three machine learning algorithms, viz., the K-Nearest Neighbor (K-NN) algorithm, Support Vector Machines (SVM) and decision trees are used for classification. During dynamic tests, the model is excited with a uniaxial shake table which has a 40 kg payload capacity, and the responses are obtained using accelerometers. To categorise the structural states, the extracted data is split into three sets (set I, set II, and set III) with variations in training and testing data samples and fed through the aforementioned algorithms. It is concluded from the study that the linear SVM is highly suited for set III with 98% accuracy, while fine tree and fine kNN are best suited for set I data with 98% and 97% accuracy, respectively. Also, ML technique has the ability to handle massive data with utmost prediction.

This paper presents the findings of the incremental dynamic analysis of a two-bay, four-shelf selective pallet rack along the down-aisle direction under a set of far-field and near-field ground motions. The numerical study employs a pivot hysteresis model to simulate the hysteresis behaviour of the connections between the beam and upright. The approach proposed by Firouzianhaji is implemented to derive the backbone curve of the hysteresis model from the results of the monotonic cantilever tests. The study examines two cases in which the total mass of the pallets is either 8000 kg or 4000 kg, with the total mass distributed uniformly on all four beams of the shelves for either case. The results indicate that racks supporting a heavier pallet mass of 8000 kg mostly have lower frame capacities than racks supporting 4000 kg of pallet mass. The structural behaviour of the racks shows characteristics similar to a soft story, with larger values of connection rotations and shelf-level displacement observed at the first shelf level. The frame capacities of specific pallet racks are notably reduced when subjected to near-field ground motions with a higher PGV/PGA ratio (exceeding 0.2), highlighting the potential for collapse in these earthquakes. Fling-step type artificial pulses generate larger responses compared to forward-directivity type pulses, for the same acceleration amplitude, with the response parameters indicating higher values for fling-step type pulses at a period ratio of 1.2 and for forward-directivity type pulses at a ratio of 1.0.

The application of Fibre Reinforced Polymer (FRP) as a strengthening material for Reinforced Concrete (RC) structures is gaining popularity. Conversely, the vulnerability of FRP to high temperatures is also a significant concern. Hence, a fire-resistant insulation layer is able to protect FRP and ensure that the strengthened RC structures satisfy the minimum fire requirement. Cementitious composite is reported to have better performance, higher economic value and greater sustainability than other commercialised insulation materials that can acquire minimum fire resistance. However, no previous studies have been found that discussed the thermomechanical behaviour of insulated FRP-strengthened RC structures exposed to ASTM E119 for fire endurance testing of structural assemblies. This study investigates the behaviour of a strengthened RC column layered with cementitious composite when heated up to 1000℃ for at least 2 hours. Finite Element (FE) analysis was used by simulating the model’s thermomechanical behaviour, and validated by the experimental data. The thermomechanical properties of the RC column strengthened with cementitious composite containing polypropylene (PP) fibres and Ground Granulated Blast-furnace Slag (GGBS) in different levels of thickness were assessed. The study found that 40 mm was the optimum thickness of the insulation layer applied to the RC column strengthened with Carbon FRP (CFRP) that acquired fire resistance of at least 2 hours.

Many of the existing age-old bridges connecting railways and highway networks need to be assessed for their structural integrity, degradation due to ambient load effects and environmental conditions and adequacy to the increased load demands. Field testing and evaluating the structural performance of bridges is becoming essential as most of the bridges that are serving are becoming old and deteriorating because of environmental effects, increase in vehicular loading, poor maintenance etc. In the present paper, detailed investigations carried out on an age-old in-service open-web girder type long-span rail-cum-road bridge through extensive instrumentation and field testing are discussed in order to assess the failure of the members, excessive vibration and to formulate appropriate retrofitting procedure. As the bridge experiences distress and damage on some of the members, it became necessary to investigate and assess the structural performance of the bridge through sensor based response measurements assisted with analytical studies. Instrumentation and field testing of the bridge has been carried out to measure the structural and vibration responses of damaged and undamaged portals of one of the bridge span under moving vehicular and train loading. Numerical modeling at both global and local level is carried out to simulate the responses obtained from the field testing. It is found that, the cross girders of the portal at intermediate expansion joint locations are subjected to excessive torsion due to improper seating of the stringer beams at the edge of the cross girder flange. By assessing the requirement and envisaging the practical suitability, a suitable retrofitting scheme is designed.

Research efforts are being continued for better understanding and modelling of lock-in phenomenon on circular chimneys due to vortex shedding, since the role of Reynolds number and turbulence intensity on various aerodynamic and aeroelastic parameters are not fully understood in the literature. In this summary paper, salient features of Vickery and Basu spectral model and Ruscheweyh correlation length model are briefly explained. Currently, these methods are widely recommended in international codes of practice on chimneys. Recent development by Lupi et al. on improving the aerodynamic damping in the spectral model, is also described and discussed. Further, details of development of a new semi-empirical model by the author, based on research study conducted at CSIR-SERC, and subsequently at JUET, Guna, are also presented which show a promising potential for prediction of across-wind response under lock-in condition. The method provides a closed-form solution which is useful and easy to adopt by the designers. Importance of application of machine learning based GBRT algorithms for wind engineering problems is highlighted.

Prestressed concrete composite girders with concrete flanges and corrugated steel web are being widely used for construction of bridges all over the world owing to their suitability for wide ranging bridge deck systems, such as girder-slab bridges, continuous bridges, box-girders, extra dosed and cable stayed bridges. The composite girder with corrugated steel web possesses several advantages, such as lightweight, prestressing efficiency, aesthetical appearance, suitability for earthquake prone areas and economy. These type of bridge girders are relatively new to India and guidelines for their design are yet to be codified. In this paper, different parameters which would aid in the design of composite girders with corrugated steel web are discussed. Further, details of innovative embedded shear connection developed for concrete flanges-steel web connection of composite girders are also presented. The load-slip responses of composite girders with embedded shear connections for different depths of embedment and varying dowel reinforcements are discussed. The importance of design equation proposed for predicting the shear resistance of the embedded shear connection is highlighted. Studies reported on performance of composite girders with corrugated web are also presented briefly to put forward the merits of these systems for adoption.

The spectral analysis of the structural waveguide leads to the dispersion relation, which shows the behavior of the different wavemodes with frequency. It helps in ultrasonic-guided wave-based non-destructive inspection to choose an excitation frequency based on the choice of the excitation wavemode(s). The dispersion curves for a waveguide with simple defect-free geometry work well for their inspection. However, the presence of any defect, e.g., delamination or cracks, affects the behavior of the propagating waves used for diagnostics. Therefore, it is necessary to perform the spectral analysis of the structural waveguide with defects and study the sensitivity of dispersion curves to the defect size, location, and orientation. The dispersion curves can be obtained analytically or numerically, but these methods have inherent limitations. The analytical techniques are limited to simple geometry; however, using numerical methods, e.g., Finite Element Method for complex geometry, will require a substantial computational cost. Therefore, this paper presents the spectral analysis of the three-dimensional structural waveguide with defects using the Semi-Analytical Finite Element Method, which uses the advantages of both analytical and numerical methods. It uses the analytical solution in the direction of wave propagation and numerical solutions in the transverse directions. We have performed the spectral analysis of defect-free and defective waveguides containing defects such as cracks or delamination of varying sizes, locations, and orientations. The finite element discretization of the cross-section affects the number and accuracy of wavemodes obtained in the dispersion curves. The computed dispersion curves for defect-free waveguides are compared with those obtained from open-source dispersion computation software GUIGUW (Bocchini et al.) for the same geometry and found a good match between them. As the defects reduce the structure’s stiffness, we observed a significant reduction in the cutoff frequencies of the higher-order wave modes in the dispersion curves for defective waveguides compared to their defect-free counterparts.

Structural Fire Engineering (SFE) is important for ensuring the safety of structures / buildings and their occupants during a fire. Recent advancements in SFE have led to the development of fire-resistant materials and systems, as well as retrofitting strategies that aim to address challenges posed by different building types and fire scenarios. However, fire prevention and protection measures alone are insufficient. Despite protection measures, many a times structures / structural elements do get affected. Hence, post-fire assessments of the state of a structure / structural elements are essential to determine the appropriate course of actions. To improve fire safety, it is crucial to understand the role of human behaviour, education, signage, and technology. The present paper outlines various ways to reduce the risk of fire hazards, including active and passive fire protection measures and the use of smart sensors and fire-resistant materials. Additionally, the paper covers the use of passive fire protection systems and various strengthening techniques to retrofit concrete structural members, highlighting the associated developments. The paper also discusses different methods for assessing fire damage, such as colourimetry, strain energy dissipation, temperature field history calculation, and studying changes in the concrete microstructure using X-ray diffraction. Finally, the paper explores factors affecting the selection of a suitable retrofitting technique and approaches proposed by different authors to choose the appropriate retrofit methodology based on damage assessment.

Passive dampers encompass a range of non-power consuming devices that can be utilized for the mitigation of structural vibration induced by external excitation, such as wind, earthquake, sea waves, and traffic. Common types of passive dampers include friction dampers, fluid viscous dampers, viscoelastic dampers, metallic dampers, tuned mass dampers and tuned liquid dampers. Considering the relative ease of design and installation, as well as the requirement of low initial and maintenance costs, passive dampers hold tremendous potential in providing a sustainable solution to the challenge of structural protection from environmental loading. The development of passive energy dissipation devices for civil engineering structures is a fast-expanding field with significant recent progress. This paper presents a state-of-the-art review of some of the more established passive dampers used for controlling structural vibration. Working mechanisms, design philosophies, advantages and shortcomings of these dampers are discussed. The applicability of the devices is also highlighted, along with a summary of their installations in real-life structures.

This paper examines the process of designing shell structures by selecting necessary forces to ensure the shell can bear applied loads primarily in axial compression with minimal bending. Instead of following conventional methods, the designer assumes a desired state of stress and determines the corresponding funicular shape using various boundary conditions. Two-dimensional structures result in funicular cables or arches, while three-dimensional structures are known as funicular shells, and domes derived from these shells are called funicular domes. Different numerical methods, such as Finite Difference, Finite Element Method, Boundary Integral Element, and Differential Quadrature Methods, can be used to obtain the funicular shape of a shell. This paper presents examples of cables, shells, and domes solved using these techniques and draws conclusions based on the results. The governing equation for shallow funicular shells and domes is Poisson’s equation, while a nonlinear partial differential equation is used for deep shells and domes. Overall, this paper provides insights into the application of various numerical methods in determining the shape of funicular structures.

Supplementary Cementing Materials (SCMs) are integral to modern concrete construction. Their use brings in immense value addition to the long term strength and durability, due to their contribution to the development of a disconnected pore structure. There have been several attempts in the past to identify specific physical and chemical contributions of SCMs to the compressive strength of concrete in order to evolve a rational approach towards deciding the extent of substitution of cement. In this paper, an attempt has been made to describe the physical and chemical contribution of SCMs to durability properties of cement mortar using a methodology previously developed by the same authors.

Structural engineering has been the backbone of human development from the ancient times, and this field continually adapts and evolves by embracing innovative approaches and emerging trends to meet the ever-changing demands. In this paper, a bird’s eye view on the trends that will shape the structural engineering in near future is provided. Some of the emerging technologies such as building information modeling, artificial intelligence, machine learning, robotics, automation, that have the potential to improve productivity, safety, sustainability and resilience of the built environment are discussed. It is noted that the present day challenges require a different approach to education and innovation in civil engineering, along with leveraging technology transfer and interdisciplinary collaboration.

First-crack strength is an important design consideration for ferrocement elements such as water tanks and storage bins. Also, for ensuring durability against ingress of harmful chemicals first-crack strength can be an important design criterion. From the review of relevant literature it is noted that the literature on the topic of this paper is scanty. Hence, a probabilistic analysis of cracking stress of normal and lightweight ferrocement in axial tension is carried out using Monte Carlo simulation technique. In simulation, basic variables are treated as random and the deterministic equations proposed by Desayi and Reddy are used. By comparing the characteristic cracking stress with the experimental minimum values, design equations are proposed for normal and lightweight ferrocement elements.

The use of Carbon Fiber-Reinforced Polymers (CFRP) for reinforcing and prestressing concrete structures is a promising alternative in the infrastructure industry. Particularly, prestressed concrete members reinforced with such polymeric materials are becoming popular to evade corrosion-related issues. The conventional simply supported bridge requires bearings and expansion joints for various load transfers, mandating regular maintenance and protection from corrosion. The corrosion-related distress and additional joints directly or indirectly reduce the bridge life and increase the cost as well as maintenance activities. To avoid such challenges, the present study proposes the design of an integral bridge with reinforced and prestressed fiber-reinforced composite tendons alternative to the traditional simply supported bridge reinforced with corrosion-prone steel rebars. Herein, the Strut-and-Tie Modeling (STM) approach is followed for the analysis of the integral bridge members. Furthermore, the design of the integral bridge based on the STM approach is compared with the traditional limit state design approach. A full-scale three-dimensional (3D) Finite Element (FE) model of a CFRP composite-reinforced single-span integral bridge is developed. Stress field analysis is performed corresponding to Ultimate Limit State (ULS) combinations as per the EN 1990 Eurocode. Also, topology optimization of an idealized portal frame of the bridge is performed for the applied vertical loading on the structure. The optimized truss topology has proven helpful in reducing computational cost and time requirements using the STM approach.

Probabilistic analysis of underground tunnels is getting increasing importance as the approach can explicitly consider inherent uncertainties in the involved parameters to provide a rational perspective in the analysis and design of underground tunnel structures. In fact, reliability analysis of underground tunnels is an active field of research in recent years. Like reliability analysis of any other structure, the developments in tunnel reliability analysis approaches have also taken place under two sub-heads i.e. analytical and simulation-based approaches. Noting the difficulty of performing reliability analysis by those approaches for real-life tunnels that involves evaluation of implicit nonlinear
performance functions by tiring finite element simulation, the metamodel-based reliability analysis approach has been widely applied in tunnel reliability analysis. The present article provides an overview of related developments in analytical and simulation-based tunnel reliability analysis with special emphasis on the application of various metamodeling approaches in such analysis. Based on the overview of the developments in tunnel reliability analysis presented here, the challenges and opportunities in the field are summarized. The article is likely to augment the state-of-the-art developments of tunnel reliability analysis.

Traditional fire-resistant design methods are primarily prescriptive in nature, which ensures that the overall dimensions of the Reinforced Concrete (RC) section and cover to the reinforcement. The design of RC sections subject to axial force and bending moment during a fire requires several tests involving lengthy calculations to achieve the desired fire resistance. The paper presents a sectional analysis method for heated RC sections that defines non-dimensional capacity parameters for interaction diagrams. The application of the interaction diagram is rendered more versatile by establishing non-dimensional parameters during the fire. The study includes a heat transfer analysis for determining the thermal profile and a sectional analysis to predict the interaction curve for different fire duration intervals. The RC section was exposed to a 2-hour ISO 834 fire and was modelled by making interaction diagram coordinates independent of cross-sectional dimensions and material properties. The study comprised three different percentages of steel. The findings of numerical studies are used to quantify the effects of reinforcement percentage on load capacity. The axial and flexural capacities for the given sectional dimensions and material properties could subsequently be modified in a redesign. The proposed approach enables the design and analysis of reinforced concrete structural elements to meet specified fire resistance requirements.

Mode shapes are the predominant dynamic sensitive features for structural damage identification. This paper proposes a vibration-based bridge global damage identification technique using mode shape data. Two cases of global damages: increased boundary stiffness as a result of a damaged bearing and reduced foundation stiffness as a result of scouring are analyzed by the proposed vibration-based damage diagnostic technique. New damage indicators based on the shape change of the first mode shape gradient and root mean square difference of first mode shape between healthy and damaged bridge are proposed for bridge bearing and scouring damage identification. Numerical simulation studies have been carried out on two bridge models: i) single-span bridge: simply supported beam with damaged bearing supports (i.e. with varied levels of rotational spring stiffness) and ii) multi-span bridge: four simply supported beams resting on sprung piers and foundations (i.e. with varied levels of foundation spring stiffness) to demonstrate the proposed mode shape based global damage identification technique. Investigations concluded that the mode shape gradient amplifies the effect of changing support stiffness due to bridge bearing damage and serves as a better feature for bridge bearing damage identification over natural frequency change and change in mode shape amplitudes and other higher order mode shape gradients. The change in the trend of the first mode shape gradient from sigmoid shape towards an approximate sine wave shape robustly confirms the bearing seizure. The relative change of mode shape amplitudes at damaged pier and root mean square difference between healthy and scoured mode shapes confirm the bridge scouring damage. The proposed mode shape-based indicators are effective in bridge global damage identification.

This article reports a comparison between the internal damage growth in cementitious materials without fibres and with fibres subjected to elevated amplitude cyclic compressive loading. The damage progression was assessed using ultrasonic testing method and Acoustic Emission (AE) testing. The intricate fracture mechanism in the test specimens causes rise to a higher harmonic generation, which was used as an indicator to the internal damage. The decrement in wave peak amplitude with higher harmonic generation may be regarded as a ‘internal damge growth’ in the deformable solid. The complexity in the fracture mechanism in fibrous cementitious matrix influenced the heterogeneity of the specimen, which is reflected by the steep decrement in the slope of the line plotted using normalized higher harmonic ratio and load. It was observed that the ‘magnitude of the total damage’ developed in plain concrete at the last loading phase was relatively lower than brass coated steel fibre reinforced concrete. This was supported by the damage parameter based on generated AE, where final failure of the specimens preceded an AE avalanche. Therefore, the utilization of a combination of nondestructive testing techniques such as AE and nonlinear ultrasonic testing can offer a more comprehensive understanding of the progression of damage in quasi-brittle cementitious materials.

The Reinforced Concrete (RC) terrace slab is the most vulnerable element in RC structures and is subjected to distress at early ages due to the corrosion of embedded steel rebars. An overlay of Polymer Modified Concrete (PMC) is a viable option to protect the reinforced concrete slab from water penetration and prevent premature corrosion of steel rebars. This study investigates the influence of styrene acrylate co-polymer modification at 2% by weight of binder (bwob) on the durability and microstructure properties of Ready-Mix Concrete (RMC). Concrete specimens were cast to perform compressive strength and durability tests such as water sorptivity, absorption, and accelerated corrosion tests. Samples were also characterized at 7,14, and 28 days using SEM with EDS and FT-IR. Test results revealed that the styrene acrylate modification in RMC at the dosage of 2% did not negatively alter the compressive strength of the concrete at 28 days. The Polymer-modified Ready-Mix Concrete (PRMC) exhibited (i) increased time for initiation of cracks and high resistance to the passage of electric current; (ii) improved water impermeability as compared to RMC, and hence improved durability properties. The SEM with EDS analysis revealed that the Ca/Si ratio of both control and PMC concrete was in the range of 1.5 to 2.3. The polymer modification in RMC modified the morphology of the hydrated product at 28 days, and the CSH gel formed appeared to be thick needle-like structures as compared to plate-like CSH gel formation in RMC. From this study, it can be concluded that polymer modification at 2% bwob appreciably improved the durability properties of RMC with similar 28 days strength development and hence recommended for use as an overlay for corrosion protection in reinforced concrete terrace slabs.

The present paper aims to prove the effectiveness of steel-concrete composite building over conventional RC building when subjected to seismic load. The steel-encased sections of the composite building are designed as per the criteria prescribed in the Eurocode EN 1994. The seismic performance of the composite building and the RC building is estimated through the analytical fragility function. Further, the pushover analysis is performed by assigning the user-defined hinges to frame the elements of the composite and RC buildings. The pushover-based fragility curves are developed for the various damage states. The median capacity and standard deviation for the different damage states of fragility curves are estimated by using the previous literature. Finally, it is proved that with the inclusion of the steel-encased profiles in the building, the seismic performance of steel-concrete composite building has increased in terms of strength, stiffness, ductility and damage pattern compared to conventional building.

Rapid population growth, urbanization and shortage of conventional construction materials are delaying infrastructure development. Labor shortages in conventional construction practices widen the gap between demand and supply of residential units. The precast lightweight panel construction can be a feasible solution for the above problems, In particularly, needs focused research towards the development of wall and the roof components, which are the major parts of building construction both interms of material and budget requirements. Limited research work is carried out on precast lightweight large wall panels and one way roof slab panels. Usage of one-way slab panel is not fully accepted by the construction industry due to its complication in leak proof in between the one-way slab and hence, it is presently managed with in-situ two-way slab construction. Considering the above, The present paper investigates room-sized large lightweight roof panels for two-way slab applications. The roof panel is fabricated using the standard, market available expanded polystyrene (EPS) panels of size 1200 mm x 3000 mm x 100 mm is suitably modified to a size of 3000mm x 3000mm x 100mm, and then sandwiched using 25 mm thick M40 grade concrete ferrocement wythes arround the EPS panel. Considering the requirement of UDL load applications, a novel 12-point loading mechanism is devised for simulating equivalent uniformly distributed conditions, for studying its two-way flexural behavior. A nonlinear finite element analysis is performed numerically for ascertaining the performance of the panel for both udl and 12-point loading cases, and the results are found comparable. The strain gauges are pasted in both steel and concrete portions and placed LVDTs to observe the deflected pattern. The panel first cracked at a load of about 91 kN which is equivalent to the UDL distribution is 10.11 kN/m2. The first crack load is found well beyond the factored design load in a normal residential building, which is about 1.7 times lesser. The panel reached its ultimate load when it reaches 195 kN. The experimental results are compared with numerical results and found comparable with lesser than 10% variations untill the slab starts cracking. After cracking, the experimental results shows excessive deformation compared to the analytical results due to the support uncertainaties. From the deflected shape and the crack pattern shows a typical two-way slab action. The sandwich roof panel is outperformed and exhibited better performance which is more beneficial for the precast industry.

Shear Strength of concrete is one of the important criteria for the analysis and design of structures as it causes the sudden failure and becomes catastrophic. There were several studies on the behavior of shear strength of concrete beams but still there is a scope for further investigation on High Strength Concrete (HSC) beams. In the present study two grades of reinforced concrete beams with three shear span to depth ratios (a/d) 1, 2 and 3 for each grade were considered. The beams that were cast and tested experimentally were modelled and tested in numerical based software ATENA. In ATENA, for assigning the material for concrete the cementitious2 and cementitious2 user model was considered. The cementitious2 model consists of Euro-code and model-code as default models, both of them were used in the study to determine the shear strength of reinforced concrete beams. In cementitious2 user material model, the compressive stress-strain model can be user defined in which, the GRK Stress-strain model and Mander’s stress-strain model was given as input to find the shear strength of reinforced concrete beams. The shear strength of the test specimens increased with increasing concrete strength for all a/d ratio values. With the increase in a/d ratio from 1 to 3, the shear strength is found to reduce by about 60%. The strains observed in numerical study indicate that the beams have failed in shear which is similar to experimental results. The shear strength obtained using ATENA with various models was compared with the experimental results and it was found that all the shear strength values were in similar behaviour with experimental results.

The response of steel Moment Resisting Frames (MRF) under seismic excitations is largely governed by the characteristics of beam-to-column connections. The seismic design of steel structures require that the “dissipative zones” intended to dissipate the input seismic energy are correctly identified based on the type of connections envisaged during engineering phase. Though extensive studies are reported in literature regarding response of beam-to-column connections under various types of loadings, it is strongly felt that a systematic joint characterization procedure required for seismic assessment of steel structures is still missing. Such a procedure will be eventually beneficial to the design engineers and researchers to ensure that the global seismic analysis is compatible with the assumed connection characteristics. The paper presents a detailed procedure for the characterization of beam-to-column joints necessary for seismic assessment of steel MRF structures. Extended end plate beam-to-column connections namely haunched, unstiffened and stiffened each of them representing full-strength, partial-strength and equal-strength design objectives are considered in the study. The characterization proceeds with development of moment-rotation curves using both the component method of Eurocode-3 and the Component Based Finite Element Method (CBFEM). The capacity design verifications of the connections for the assumed overstrength are then performed using CBFEM. Finally, the hysteresis behaviour of the connections under cyclic loads, where required, is predicted using the modified Richard - Abbott model.

Sleeved Column (SC) System, a novel compression member that consists of an inner core made of steel rods surrounded by a steel sleeve provides an improved resistance to buckling load and enhances the compression resistance almost equal to Euler’s buckling load. The load carrying capacity of sleeved column system is significantly affected by the stiffness of core. SC system usually consists of single or group of steel rods in the core to resist the given axial force. This study presents a SC system with combination of High Tensile Steel (HTS) and Glass Fibre Reinforced Polymer (GFRP) rods in the core called as “Hybrid Steel-FRP Sleeved Column” (HSFSC) System. The gap between sleeve and the core is grouted with geopolymer mortar. The conventional SC specimen consists of HTS rods in the core surrounded by a thin walled steel sleeve. The HSFSC specimen consists of various combinations of HTS and GFRP rods in the core surrounded by mild steel/GFRP sleeve. The performance of HSFSC system against the conventional SC system under axial compression load is studied by conducting experiments..

Steel-concrete composite floors are recently more popular in buildings. Double skin steel-concrete composite slabs offer high degree of flexural rigidity, strength and ductile resistance than conventional decking slabs. Double skin composite is a new method of construction consisting of thin steel plate as the outer skins connected together by shear connectors and infilled with concrete. This type of construction is an extended form of conventional composite deck floor used worldwide, which utilizes profiled steel sheet on one side topped with reinforced concrete. A Steel-Foam Concrete Composite (SFCC) slab made of corrugated light gauge steel sheeting on both sides and aerated low-density foam concrete core is developed and the details are presented. Normal and shearing forces are transferred between steel sheet and foam concrete core using through-through mild steel studs which acts as transverse shear reinforcement. The perceived novelty of the proposed SFCC slab is that the outer profiled steel sheets on both sides acts as reinforcement as well as permanent formwork which eliminates the conventional formwork and expensive detailing, bar bending and fixing of reinforcement leading to substantial economy. The low density foam concrete offers thermal comfort and reduction in the dead weight of the panel by 10% compared to conventional flooring systems. Full scale flexural tests are conducted on SFCC one-way slab to obtain its flexural strength, ductility and load-deformation behaviour. The ductility and strength aspects of SFCC one-way slab are remarkable and is recommended for use as floor/ roof slabs in buildings.

The effect of span lengths and pole class on the efficiency and reliability of wood distribution poles is investigated. Performance of 12m utility poles of class 1 on 75m spans and class 3 on 45m spans are computed and compared. Metrics of evaluation includes the bending capacity at ground line and material costs of initial installation. Second order (P-Δ) effects and wind on pole are also considered. The main inference from the study is that poles of higher class and larger spans showed better structural efficiency and economy than those of shorter spans and lower class. Suggestions for application of this inference to other situations are made.

The mathematical reliability of wood and composite utility poles is investigated. Numerical reliabilities at factored loads for 18 poles are computed and compared. The main inference from the study is that composite poles showed higher structural reliability than wood poles. The average reliability index of composite poles is observed to be more than three times that of wood poles. It is suggested that composite poles offer better long-term performance, resilience and reliability when used in hurricane-prone areas.

Earthquakes induce large reverse cyclic plastic strains causing rapid loss of strength of materials leading to collapse of structures in a few cycles. Development of earthquake resilient steel structural systems to ensure community resilience requires accurate prediction of fracture initiation. In this work, the behaviour of tensile coupons made of mild steel (IS2062 grade) is studied. Fracture initiation under the action of monotonic tensile load is predicted by employing a triaxiality dependent uncoupled damage model based on void growth and coalescence. von Mises yield surface is considered with two different isotropic hardening models: one based on the conventional true stress-true strain relation obtained directly from the experiments, and another mixed linear-power law hardening model including the effect of necking. Fracture index of the void growth model is evaluated based on these two hardening models. The model parameters for mild steel IS2062 grade are calibrated based on experimental tests and complementary Finite Element (FE) simulations on tensile coupons of three different thickness by comparing the fracture index. The proposed model parameters will be useful for estimation of fracture initiation in mild steel components.

It is known that the reinforcement used in RC beams shall have the proper development length or anchorage length to develop its full strength and avoid premature failure. The usual practice to fulfil the code specified development length criteria includes extending the reinforcing bar beyond the theoretical cut-off point, using couplers, headed bars, bars with hooked ends, etc. This paper presents a new method of providing development/anchorage length using reinforcement with helical ends. The experimental investigation carried out in three phases to study the behaviour of RC beams provided with continuous / spliced reinforcing bars with helical ends indicated that the behaviour of RC beam with Helical end Rebar (HeR) is similar to the behaviour of conventional RC beam.

In seismically vulnerable areas, the beam to column joint is the most critical region in reinforced concrete structures. Because of the long development lengths and large bend diameters, the arrangements for straight bar and hook anchorage in structural concrete create practical problems. Proper anchorage and joint details of reinforcement are essential. The innovative joint designs that can reduce congestion of reinforcement in the joint are desirable. The present study aims to compare the behaviour of exterior beam-column joint with the use of the threaded bar and steel fibers in place of conventional joint detailing. Six joint sub assemblages were tested under reversed cyclic loading. The displacement-controlled reverse cyclic loading was applied at the free end of the beam. A 3D numerical model has been created using the ABAQUS 6.14 software. The Concrete Damage Plasticity (CDP) model was used to define the non-linear features of concrete by analyzing the response of the structure. The performance of an alternative joint detailing, which is practically feasible, is compared with that of a conventional ductile detailing in terms of ultimate load, hysteresis behaviour, crack pattern, energy dissipation, and ductility. The average difference between FEA results and experimental results was less than 5%.

Periodic inspection of reinforced concrete bridges and buildings is required to assess their deterioration due to loading and environmental factors. Monitoring the condition of the existing structure helps in the assessment of its load carrying capacity. Cracking in concrete structure is one of the critical parameters representing its structural health. Trained personnel monitor the development of cracks and their progression at the critical locations of the structures through a physical vision at regular intervals of time. With the advancement in computational techniques, machine vision is becoming a robust alternative to physical inspection of the structure and its health monitoring. The present work demonstrates the application of machine vision in concrete crack monitoring by identifying the location of the crack, the number of cracks, the length of the cracks, and the area of the cracks. A novel system has been developed by integrating machine vision and convolutional neural networks to gain real-time images of concrete surfaces, detect concrete cracks, and extract various parameters related to cracks, such as number, location, length, and area, in synchronization with the applied loading. The present system is implemented for real-time crack monitoring during compression testing of concrete cubes of size 150 mm × 150 mm × 150 mm of different characteristic strengths. The outcome of the machine vision system in graphical form is presented for various parameters of cracks like the number, location, length, the area concerning compressive load for concrete of different strengths. An accuracy of 98% has been achieved for crack detection on concrete cubes as presented in the results. The present machine vision system can be implemented on different concrete structures for acquiring real-time data on crack development and progression. The proposed framework will be an effective tool for engineers working in the domain of structural health monitoring of concrete structures.

Plate girders are widely used in long-span applications. Patch loading is one of the most typical loads a plate girder is subjected to. These partially distributed loads traverse along the span of a plate girder’s top or bottom flange. Length and number of patch loads are the governing factors that decide the system’s patch load capacity. The present study conducted a numerical investigation using finite element models developed in ABAQUS®. The existing experimental results in the literature were used to develop the numerical models and then validated against the results obtained from experiments. The effect of plate girders subjected to multiple patch loading was also evaluated and compared in this study. The spacing of patch loads allows for the distribution of the load to a larger area and influences the patch load capacity. The effect of multiple patch loads on longitudinally stiffened and unstiffened girders was evaluated. The optimum position of longitudinal stiffeners was found for girders subjected to multiple patch loading. The effect of different stiffener arrangements was assessed to find the most effective arrangement for efficiently resisting patch loads. Stiffeners placed close to the loaded flange were found beneficial in patch load resistance.

The Modified Compression Field Theory (MCFT) and the Softened Membrane Model (SMM) can be used to predict the non-linear behaviour of a wall-type Reinforced Concrete (RC) structural member under increasing in-plane shear stress due to lateral loads generated during an earthquake. The present study is based on the SMM. This model considers an orthotropic formulation of the in-plane strains to incorporate the Poisson’s effect in a membrane element. The formulation assumes that the reinforcement grid is symmetrical with respect to the principal axes of applied stresses. In the present study, a two-dimensional anisotropic formulation is used to extend the applicability of SMM to an element where the symmetry of reinforcement is not maintained. This formulation is a mechanics based approach to consider the shear strain generated due to the principal stresses in addition to the normal strains, which is referred to as the effect of shear-extension coupling. A model is proposed for the estimation of this shear strain based on test results from the literature. Next, the solution algorithm of SMM is generalised to incorporate the proposed model. The modified algorithm is corroborated based on the predictions of the behaviour of a series of RC panels tested under increasing in-plane shear stress.

When biogenic acid reacts with cement hydrates, physical and chemical changes occur in the cement mortar, which can cause premature deterioration of exposed concrete structures. The present study evaluates the performance of chemical admixtures, viz., styrene acrylic ester based polymer (SAP) and sodium nitrite based corrosion inhibiting admixture (SNI) in cement mortar exposed to two strong inorganic acids, hydrochloric acid (HCl) and sulphuric acid (H2SO4). Its aim is to investigate the potential chemical changes in exposed cement mortar to properly understand the degradation mechanism by these acids. Post-exposure evaluation investigates the changes in the strength, variations in length/mass of the specimens, and variations in the pH of the leachant (exposed medium). Fourier transform infrared spectroscopy (IR) was performed to analyse the associated chemical changes in the cement mortar due to acid exposure. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS ) were used to study microstructural transformations and final phase products associated with the chemical changes. Findings from the study reveal higher degradation caused by H2SO4 medium than HCl medium, irrespective of SAP/SNI incorporation, due to a significant difference in their mechanisms of attack, which was linked to their calcium salt solubility along with its adhering affinity to the cement matrix. Due to its instability in acidic media, SAP incorporation into cement mortar results in inferior performance compared to control mortar. The overall performance of SNI addition in cement mortar was found to be significantly superior to control mortar in post-exposure evaluation. Results from IR analysis along with SEM-EDS characterization confirm the least deterioration and improved microstructural properties of cement mortar admixed with SNI

Owing to the strict provisions in implementing novel concrete like geopolymer concrete for construction applications, it is imperative that the development of the concrete and its properties there of takes priority. In the present work at the outset aggregate optimization based on particle packing theory (MTM and JDD) is taken up to develop the GPC. Then the prediction of the bond performance of such a sustainable concrete is attempted. The study compares the bond performance of geopolymer concrete based on numerical simulation of pull-out test as per IS 2770 Part-1 with varying embedment lengths and diameter of the reinforcement bar for different grades of Geopolymer concrete. Simulation of the beam-end pullout test is attempted with parameters including embedment length to rebar diameter ratio, concrete cover to rebar diameter ratio for grades of geopolymer concrete and an analytical equation to predict bond strength of geopolymer concrete is proposed. It was concluded from the studies on bond performance of geopolymer that the bond stress has an inverse relationship with embedment length, direct relationship with concrete cover, and grade of concrete. whereas, the change in diameter of the rebar has no significant effect on the bond performance of geopolymer concrete. The proposed analytical equation is found to yield satisfactory results in predicting the bond strength based on numerical simulation.

In the last few years, the application of variational approach-based phase field model in fracture mechanics has gained attention for simulating complicated crack behavior. The phase field model does not require the presence of predefined cracks. Crack path in the phase field model for damaged material is tracked by a phase field variable that varies between 0 and 1. This paper aims to carry out fracture analysis of quasi-static brittle specimen under plane stress and plane strain conditions using phase field method. Phase field modelling for two-dimensional quasistatic brittle fracture has been implemented using user-defined subroutines in ABAQUS software. Centre-notched specimen under mode-I and mode-II loading were analysed and the predicted behaviour compared with the literature. The effect of thickness on load carrying capacity of specimens were investigated and it was observed that for similar thickness, load carrying capacity is higher and occurance of fracture delayed in plane stress condition as compare to plane strain case. Other observations from the study include that thickness does not have any effect on the displacement at which sudden fracture occur, in both plane stress and plane strain cases.

This study aims to carry out investigation of functionally graded skew sandwich plates with geometrical deformations under hygro-thermo-mechanical loading. It is performed using Higher Order Zigzag Theory (HOZT) and dimensionless deflections and stresses are obtained. Using HOZT, the criteria of continuous transverse shear stress at inter-laminar junctions and zero at the top and bottom surface of the plate is fulfilled. It thus eliminates the requirement of factor for shear correction. The material properties follow the power law variation and are dependent on temperature and moisture conditions. The temperature distribution is assumed to be linear and moisture distribution is assumed to be constant in the study. A 9-noded finite element with 11 dofs at each node is used for discretization of the plate. The influence of governing system components such as aspect ratio (a/h), volume fraction index (n), skew angle, boundary conditions, geometrical deformation types such as sine, global and local type and deformation amplitudes (ζ0) on dimensionless displacement and stresses is studied. The outcomes from this study are confirmed with those from the previous studies to authenticate the present formulation. New findings are put forth which can be used as reference for future studies in the similar field.

Seismic safety evaluation of existing building is a challenging task due to the non-accessibility of structural details. Studies are reported in literature on application of system identification techniques for extraction of modal properties of existing structures for damage detection and health monitoring objectives. Present study aims at identifying a simplified methodology to determine the mass and stiffness properties of a system for which the input and output acceleration responses are available. The methodology has been demonstrated for a three storey steel frame with RC slab for eight earthquake time histories using shake table test results. The modal parameters such as frequencies, mode shapes and damping ratios of the building are estimated using frequency response functions. Vital structural parameters governing the dynamic response of the building viz., mass, stiffness and damping are obtained using the frequency characteristics extracted. The proposed methodology can be used for obtaining the frequencies, mode shapes, mass and stiffness matrices of the structure, where access to structural details are limited.

Cement manufacturing is one of the major causes of carbon dioxide (CO2) emissions. The construction sector focuses on sustainability as a key factor in reducing stress on the environment by implementing innovative materials and techniques. The application of geopolymer concrete (GPC) is one such emerging technology in reducing CO2 emissions by completely replacing cement. In this research, it is intended to prepare alkali-activated GPC having a compressive strength of 30-40 MPa using industrial wastes i.e., Fly Ash (FA) and ground granulated blast furnace slag (GGBS) as binders. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as alkaline activators while natural sand (river sand) and Crushed Stone Sand (CSS) were used as fine aggregates and Crimped Steel Fibres (CSF) were used in synthesising the GPC. Results showed that the maximum compressive strength of was observed to be 46 MPa and 45 MPa for river sand and crushed stone sand utilised GPC respectively using 5 molar NaOH and Na2SiO3 solutions under ambient curing conditions. Furthermore, the addition of CSF showed significant improvement in mechanical properties such as tensile strength, shear strength, flexure strength and bond strength of GPC. This synthesized GPC can be effectively applied for various applications such as building construction, precast structural components, road construction etc.

First time, based on three dimensional (3D) piezoelasticity, an analytical solution has been developed for the static analysis of hybrid piezolaminated cylindrical shell panels. Furthermore, the present solution can provide results for the shell panels with arbitrary boundary conditions. The boundary conditions can arbitrarily be simply-supported, clamped or free along with electrical closed or open circuit conditions. Due to such boundary conditions, the developed stress concentration zones are accurately predicted considering the singularities which are inherent to cylindrical shell structures. As the Reissner’s type mixed variational principle has been employed to obtain the governing equations, the displacements and stresses are equally accurate at every point in the domain. The Partial Differential Equations (PDE)s are converted to systems of simultaneous first order Ordinary Differential Equations (ODE)s using the Extended Kantorovich Method (EKM) of which the set of ODEs with variable coefficients along the radial coordinate direction is solved by a modified power series method. And, the set of ODEs along the circumferential coordinate direction is solved using the Pagano’s approach as it has constant coefficients. New benchmark results have been presented after thorough validation for multi-layered hybrid composites. This development will benefit in revisiting or developing other 2D/1D solutions.

Retrofitting of existing structures is one of the most environment friendly, sustainable, and effective ways to improve a structure’s energy performance. High strength Fiber Reinforced Polymer (FRP) offers colossal potential for light-weight and economic retrofitting of concrete infrastructure through external bonding of concrete components and enhance their load carrying capacity (both flexural and shear). In FRP strengthened structures, defects can initiate during or after the retrofit process, and several factors can attribute to those defects, such as improper installation, lack of adhesion due to environment conditions, concrete cover separation, intermediate shear or flexure crack induced interfacial debonding, etc. The common and major source of defect in FRP strengthened concrete beam takes place between the composite and concrete. Hence, the integrity and durability of FRP strengthened concrete structure remains as foremost concern in ensuring the safety and performance of the FRP retrofitted structures. In the present study, ultrasonic wave propagation technique is used for nondestructive evaluation (NDE) of FRP retrofitted beam. During specimen preparation, CFRP laminate is pasted on the concrete beam (150 mm × 200 mm × 1300 mm) using epoxy as the adhesive and the artefacts are used to simulate the flaw in the epoxy layer. An attempt has been made in this research to detect the flaw in CFRP laminate strengthened concrete beam by employing the linear and nonlinear ultrasonic methods: Time of Flight (TOF), attenuation, wavelet energy, dynamic time warping, hilbert phase, side-band energy and Sideband Peak Count Index (SPC-I). The results show that, the methods that are failing to show good trend in lower frequency excitation, may exhibit extraordinarily good trend with higher frequency. The study infers that, the waves change their travel path due to de-bonding and propagate rapidly until it reaches the bonding phase and hence results in reduction in TOF. The sensitivity analysis is also performed to figure out the most efficient ultrasonic methods for identifying the flaw in the epoxy layer. SPC-I has given a clear and steady trend of increment in lower as well as higher frequency transmission. The proposed non-invasive NDE using the nonlinear ultrasonic (NLU) technique is found to be very promising for integrity assessment on the underlying flaws in the FRP-concrete composite system.

Railways is a major mode of transportation for passengers and freight in India. Hence, monitoring the health of rail sections is of paramount importance from the viewpoint of passenger safety and economy. Rail sections are prone to damage/defects; thus, their detection and localization are the primary objectives of health monitoring so as to take prompt and necessary remedial measures. In this respect, the Non-Destructive Testing (NDT) technique is effectively used for health monitoring of rail sections. Among the many NDT techniques, the Acoustic Emission (AE ) technique is more effective as it helps in damage investigation of rail sections in real-time. In the AE technique, the initiation or growth of damage emits AE waves which are captured using AE sensors mounted on the rail section, and hence, the damage itself acts as an AE source. Major requirements for localization of AE source are finding the AE wave velocity in the media and Time of Arrival (TOA) of AE wave at the sensor(s). In most of the existing methods, the wave velocity is either taken from prescribed sources or is found out through mathematical formulation using the standard properties of the material. But in real-life scenarios, the material of the system may not always be homogeneous and isotropic. Moreover, there is a possibility of existing internal defects or discontinuity etc. inside the material. Therefore, the theoretical wave velocities may often result in erroneous AE source localization. In this context, Ultrasonic Pulse Velocity Method (UPVM) can be utilised to find out the wave velocity in field conditions of the material for rail section. As field measurement of the velocity of rail section using UPVM gives correct information about the rail, the localization using the velocity will be more accurate than the conventional approach followed in the AE technique. Existing literature reviews show that no such investigation in regard to localization of damage using AE along with UPVM has been reported. This seems to be an innovative and accurate approach in heath monitoring of rail section using AE technique. In the present study, a novel approach is proposed for AE source localization whereby a combination of AE technique and UPVM is utilized. In this method, UPVM is used to predict the velocities of the AE wave in the rail section while the obtained wave velocities are utilized through Wavelet Transform (WT) based signal analysis to determine the TOA. The present method is demonstrated through experimental investigation on a rail section (1.9m) of the Indian Railways, in laboratory conditions. A single AE sensor is used to capture the AE waves in different parts of the rail section, e.g. top flange, web and bottom flange, while the AE source is simulated by Pencil Lead Break (PLB). The AGU-Vallen wavelet transform tool has been used to process the AE signals. A comparison of localization results obtained using the proposed technique and the existing technique is done. It is observed that the AE source can be localized very realistically in the Indian rail section using the proposed technique and it is found to be better in such prediction than the existing methodology. It can be concluded that the proposed approach is a very promising and more field-oriented damage localization method for rail sections. It is also worthwhile to mention that error in damage localization is reduced remarkably when obtained through the velocity measurement using UPVM than using the conventional approach, where theoretical velocity is used. The final results for localization are found to be with the lowest error of 0.129%

The process of monitoring the health of civil, mechanical and aerospace structures, to ensure their continuous functioning, without any undesirable changes in their prescribed state, is popularly known as Structural Health Monitoring (SHM). SHM is being performed in two ways: global and local SHM. For global SHM, sensors are needed to be mounted in the critical areas to obtain the inputs such as excitation loads and outputs such as responses of the structure. This imposes difficulties such as cost, time and efforts to install, operate and maintain the instrumentation, cables, data acquisition and communication systems. The effective local SHM, which predominantly uses non-destructive testing methods such as X-ray, impact echo, ultrasonic methods, thermography, and Ground-Penetrating Radar (GPR), on the other hand, incur huge costs for the specialized equipment. Also, other issues such as inaccessibility of regions for instrumentation and stalling of structures during operation for monitoring are posing challenges in the existing global and local SHM approaches. Recently, with the low cost and effective imaging hardware combined with the robust computer-vision techniques, there is a greater shift towards the computer-vision based SHM, which can alleviate the challenges of other existing SHM approaches. In this paper, an effort is made to identify and classify the images into two classes (cracked surface and uncracked surface), using an improved version of Gaussian Process (GP) models in its regression form. The benchmark image datasets with and without cracks on the surfaces of concrete bridge decks, published by Utah State university, USA, are used for validation studies. Also, the paper compares and evaluates the performances of the various kernel functions used in the GP model during regression.

The traditional system identification techniques using modal analysis assume the system as linear which may not be valid in the case of structures exhibiting breathing crack behavior during the initial damage stage. Detection of nonlinearity in the case of weakly nonlinear structures is essential for the detection of incipient damages as well as the initiation- and propagation- of cracks. Time series analysis techniques are found to be effective in extracting the nonlinear features for the characterization of system dynamics for timely fore-warning of failures. One of the promising features is the changes in phase space topology (derived from time-series information) for the detection of nonlinearity in dynamic responses of a damaged structure. In this paper, phase space topology is constructed using the acceleration-velocity-deflection responses obtained from controlled force excitation to a reinforced concrete bridge girder-deck structure at different stages of damage. Phase space trajectories from the intact and damaged structure (at different levels) are used to evaluate damage progression from the formulated dissimilarity methods. The integrity of the structure including the initial stage of damage is assessed based on dissimilarity features formulated by the change in the dynamics of the nonlinear system and determined through time-series based statistical shape analysis. The distortion in phase space topology is found to be an efficient nonlinear damage index feature and is very sensitive to the damages of low magnitude, distinguishing the structural nonlinearity from material one. It can thus be an effective tool in identifying the damage initiation through nonlinear features which form the base for structural health monitoring of weakly nonlinear civil infrastructures.

Structural health assessment is an age-old challenge. Structural health monitoring is relatively recent topic of interest. However, despite enormous developments, successful implementations of these concept are limited. In the past, identification of defect locations, numbers, and their severity were emphasized using structural behavior at the time of inspection assuming the whole structure was inaccessible for visual and other forms of assessment. To minimize the economic losses, only part of a structure was inspected, and the information was used to assess the health of the whole structure without disrupting its normal operation. Due to inherent complexities, the area has attracted a multidisciplinary research interest. Recent catastrophic failures of older or buildings under construction added a new dimension to the overall problem. In this scenario, types of defects, locations, and their severity were known. Rehabilitation actions were proposed but not acted upon in a timely manner due to lack of resources. The additional mitigation strategies for this situation has yet to be developed. Some of the related issues include who will inspect, their qualifications, legal standings of the recommendations made by them, acceptable time period to implement their recommendations, and penalty for not carrying out their suggestions, etc. In India, the initiation of a Professional Engineering license requirement, similar to the U.S., is suggested by the author to address this complicated problem.

Structural integrity of a structure is the ability of it’s components to hold together under the adverse action of rarely occurring excessive loading and aggressive environment condition. Any civil structure must be able to prevent catastrophic failure by undergoing deformation in a manner predicted during the design phase, thereby avoiding untoward incidents that can claim precious human lives and cause extensive damages. A promising technique to ensure that such catastrophic failures will be prevented is through the implementation of a robust Structural Health Monitoring (SHM) system. An efficient SHM system should be able to measure the structural deformation with minimal noise, analyse the output from the sensors installed, provide effective communication and enable the formulation of appropriate corrective action. One of the inevitable component of the structural health monitoring system is Finite Element model updation. For the past decades, there has been substantial research carried out in the field of Finite Element (FE) updating based on change in the dynamic characteristics of the structure. This paper presents a case study on health monitoring of a test bed chosen in the NITT campus using sensors, a stand-alone data acquisition system and an Internet of Things (IoT) based data transmission platform. The paper provides a method for finite element updation which plays a vital role in the implementation of real - time monitoring system. A 3D FE model of the test bed and a comparative study on influence of frequency residual, mode shape related function, modal flexibility residual and combination of all the three residuals have been done. It is observed that for updating dynamic parameters considering any one of the residual parameter in the objective function is sufficient, however for damage detection and its location, the combination of all the three residuals must be considered in the objective function to get an accurate picture of the damage. There is a brief review on various monitoring techniques practiced in the current scenario which would benefit for further research interest.

The spatial variation of ground motion due to phase lag and coherency loss effect gives rise to rotational/torsional ground motions thereby inducing additional torsional deformations. For multistorey buildings, a systematic study is reported on the effect of torsional ground motion resulting from the propagation of motion through different soil mediums: firm soil and medium-firm soil. For these soil mediums, two cases of ground motion: (i) translation ground motion only and (ii) combined translation and torsional ground motion are considered. For torsional ground motion two sets of the angle of incidence of propagating waves with vertical, 10° and 20° based on recorded values at sites, are considered. A set of twelve multistorey buildings comprising of frames or frames and shear walls is considered. These chosen buildings cover practically the entire spectrum of torsionally flexible and torsionally stiff low rise buildings. Variation of increase in storey shears along the height is studied and it is found that this variation due to torsional ground motion for some frame shear wall buildings is non-uniform along the height. Further, it is found that the increase in the response is significant for buildings, having low fundamental translational periods of vibration and that are torsionally flexible.

Modelling of support boundary condition of the shell as built in or pinned for the evaluation of the free vibration response of cooling tower shell is unrealistic. The modelling of column support and foundation with underlying soil though rigorous, requires large computational time and effort. Therefore it is proposed to evolve a simplified model to replace both column supports and the foundation on soil by equivalent support stiffness at the base of the shell as support boundary condition. The validation and effectiveness of the proposed equivalent support stiffness as support boundary condition for the tower is demonstrated by a numerical example. The sensitivity of the support boundary conditions on the free vibration response of the cooling towers is evaluated. The natural frequencies of lower modes are found to be more sensitive to the support stiffness compared to the higher modes.

This experimental investigation analyses the strength, durability and transport properties of cementitious systems admixed with sodium nitrite based corrosion inhibitor. The influence of inhibitor incorporation on workability, strength (compression, flexure and splitting tensile strength), durability (resistance to rapid chloride penetration (RCPT), accelerated corrosion (ACT)) and transport mechanism (water absorption and sorptivity) of cement concrete and cement mortar were assessed. In addition, morphology studies were also conducted through SEM. The concrete of grade M25 and cement mortar of mix ratio 1:3 were adopted. The workability of cement concrete and mortar was maintained similar, irrespective of inhibitor addition at 1%, 2% and 5% by weight of binder (bwob). It is found that the addition of inhibitor does not affect the setting time guidelines proposed by Indian standards. There is a reduction in water-cement ratio due to incorporation of inhibitor in concrete / mortar at higher dosages (2% and 5% bwob). Appreciable to significant increase in compression, flexural and splitting tensile strength for Inhibitor Admixed Concrete (IAC) as compared to control concrete, irrespective of dosage addition. RCPT test results indicate the performance grade of control and inhibitor admixed concrete as IAC5%> IAC2%> IAC1%> CC. In ACT, the performance factor was 1.3 - 1.9 for inhibitor admixed mortar when compared with control mortar. Inhibitor Admixed Mortar (IAM) also exhibits appreciable reduction in pore formation and water absorption. The SEM image analysis conducted on 2% IAM, revealed an improved microstructure and cement hydrate formation. The improved strength and durability performance of inhibitor admixed concrete / mortar may be due to (i) enhanced passivation layer on steel surface, (ii) action of chloride repulsion mechanism (iii) reduction in water-cement ratio for similar workability and (iv) improved microstructure exhibited by the ingredients of corrosion inhibitor.

For structural health monitoring of Transmission Line (TL) towers, accurate evaluation of natural frequency is one of the requirements. The damage detection studies of TL towers through change in natural frequency is gaining importance, because the stiffness loss due to damage inflicted in load bearing member of TL tower leads to reduction in its natural frequency. Further, the estimation of natural frequency of TL tower is important to evaluate its response under gusty wind and for determination of impact force under broken conductor loads. The leg, bracing and tie member of TL lattice towers are joined through bolted connections, which are modelled with conventional pin joint assumption considering only axial stiffness of joining members. However, the natural frequency predicted by using this pin joint model do not match with experimental results due to ignorance of rotational stiffness induced by eccentric load transfer. Hence, the authors proposed a modified bolted connection model considering both axial and rotational stiffness. In this paper, a semi-empirical approach is proposed for evaluation of natural frequency by using a modified bolted connection model and the same is validated with the experimental investigations on TL tower sub-panel through the push-pull mechanism. The experimentally determined natural frequency of TL tower panel is in close agreement with the natural frequency evaluated by using the modified bolted connection model. It is observed that the maximum difference in the natural frequency obtained from the experiments and the modified bolted connection model is 18% compared to 30% difference with conventional pin joint assumed in FEmodelling of TL towers. Further, the proposed method is validated on full scale prototype tested 240 kV TL tower for determination of natural frequency and the maximum difference is found to be within 12% with modified bolted connection model compared to 23% with pin joint model. Thus, modeling of flexible behaviour of bolted connection with rotational and axial stiffness plays a significant role in determining the dynamic characteristics such as natural frequency for structural health monitoring of TL towers.

Composite columns such as Concrete-Filled Steel Tubes (CFST) are widely used in construction practice on account of their improved ductile behaviour. This research work presents certain relevant aspects related to the behaviour of circular CFST columns under uniaxial compression. Load deformation, ductility factor and failure modes are studied for varying diameter (D) to thickness (t) and length (L) to diameter ratios. Initially, numerical modelling of the CFST columns was carried out using commercially available finite element software and these were substantiated by carrying out experimental studies. The strength obtained were compared using Load and Resistance Factor Design (LRFD) specifications. Further experimental studies were carried out in two phases. In the first phase, the behaviour of four CFST columns were compared to that of hollow steel tube columns for two different D/t ratios and four different L/D ratios. The second phase was an attempt to classify the CFST columns as short and slender columns based on the variation of ductility factor and failure modes (for different D/t and L/D ratios). The results show that CFST columns are more ductile than hollow steel tube columns. Variation of ductility factor was plotted based on D/t and L/D ratio. By observing the ductility factor, a limiting value of 15 was determined for D/t ratio. Also from the failure modes, it is observed that a change from short column to slender column occur at an L/D ratio of 9. The load carrying capacity of CFST columns were compared with LRFD specifications. The numerical and experimental values were found to show a variation of less than 10%.

This paper proposes a reference-free vibration-based structural damage localization technique using re-deployable mobile sensor concept and statistical signal processing algorithms. The re-deployable mobile sensor concept computes the mode shapes with the high spatial resolution by using only two sensors in contrast to the traditional high fidelity static dense sensor network which incurs huge costs and is resource-intensive. The two sensors are moved independent of the input traffic loading (position, speed and time of the vehicle covering the entire span), by progressive re-deployment in various segments along the monitored structure. The local acceleration measurements are then post-processed by a decentralized modal analysis technique to obtain a continuous global mode shape. For Structural damage localization using mode shapes, this paper employs a hybrid Continuous Wavelet Transform (CWT) – Fractal Dimension based methodology using only the output response measurements of the structure with damage. The data fusion of Katz Fractal Dimension (KFD) with CWT mode shapes help in suppressing the noise, representing the mode shapes in an enhanced time-frequency domain and intensifies the local singularities caused by the damage. Numerical and experimental investigation carried out on simple beam-like structures demonstrate that the proposed damage localization index based on CWT-KFD can able to localize and relatively quantify the damages including minor cracks and damages at more than one spatial location.

In this paper, a simplified prefabricated connection assembly is developed to act as a splice between top and bottom Steel-Foam Concrete Composite (SFCC) wall panel and also to connect with SFCC floor/roof panel at roof level of the building. The components of the connection assembly are SFCC connecting panel, top and bottom seat angles and bolts. SFCC connecting panel joins the top and bottom SFCC wall panel and is then connected to SFCC floor/roof panel by top and bottom seat angle connection by using bolts. The developed connection assembly is so devised that it develops rotational stiffness as sum of flexural stiffness of the wall panels and the floor/roof panel. The flexural stiffness of both the top and bottom wall panels is initiated by contact bearing of the both panels against SFCC panel in the connection assembly, whereas, the flexural stiffness of floor/roof panel is initiated by using top and bottom seat angle connection. In order to verify the flexural stiffness participation of the connection and the connected components, an experimental study is conducted on an exterior SFCC wall to floor joint, which utilizes the aforementioned connection. The failure is due to the plastic hinge formation in the mid span of SFCC floor/roof panel at the ultimate load of 107 kN. The connection possesses moment carrying capacity higher than the floor/roof panel capacity and is found to be adequate to be effectively used in buildings.

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Composite wall, a novel form of construction with profiled steel sheets as the facing material with an infill concrete intended for use as partition and shear walls in steel framed buildings has the potential to be used as structural elements in load bearing construction. The axial compression behaviour of two such composite walls of size (1m × 3m) and 130 mm thick utilizing profiled cold formed steel sheets of 0.8 mm thick and foam concrete of density
850 kg/m3 is studied by conducting experiments. The interaction between sheet and concrete is achieved by using through-through mild steel studs. Brittle foam concrete gained enough ductility by the steel facing and also enhances the local buckling capacity of thin steel sheet. The number of studs and their spacing are sufficient enough to cause the failure of wall panel by yielding of steel sheets rather than buckling, which is the design criteria. Composite wall panels showed gradual load-displacement behaviour up to the failure load and exhibited ductile deflections in the post-peak behaviour by sustaining almost 30% of the failure load due to the confinement action of steel sheet and the studs. The composite wall panel exhibited higher load carrying capacities and ductile deflections than conventional systems and has the potential to act as load bearing wall for G+3 buildings.

This research article presents an expeditious renovation technique for the promotion of the loading class of the through-type historic metal truss bridges. To develop this concept for real-time use, an existing bridge functional for more than 50 years was selected for the assessment. The bridge was modeled in the STAAD Pro software for the analysis of the existing state of the bridge and for the incorporation of the strengthening measures in the bridge model. The main feature of this renovation technique was the proper utilization of the open space available in the sections of the main members which overcome the deficiencies of the existing bridge in comparison to the well-designed conventional steel-concrete composite bridges and the double composite bridges. All the members were found to be safe in design and serviceability. The main concerns along with strengthening the structure were to preserve the historic appearance without replacing any member and to provide a handy and cost-effective method for the rehabilitation of such old bridges.

Steel girders with corrugated webs are gaining popularity over simple flat-web girders for their benefits, particularly in shear and torsion. Corrugations in the web enhance torsional stability and reduce the need for stiffeners. This study parametrically investigated the influence of geometric characteristics of steel I-girder flange, web, and corrugation folds on the nonlinear torsional behavior of corrugated-web steel girders (CWGs). The Finite Element (FE) modeling used in the study is validated against documented experimental results from the literature for five different loading cases applied on CWGs. In total, 35 nonlinear FE models with fixed-free (i.e., cantilever) boundary conditions were generated using various combinations of geometry parameters. The results showed that the web slenderness ratio and corrugation angle significantly influence the nonlinear torsional capacity of cantilever CWGs. Moreover, the flange width, thickness and girder span are other significant parameters affecting the torsion capacity in CWGs.

The manufacturing process of cement involves combustion of fossil fuels and calcination of limestone, resulting in emission of CO2 into the atmosphere. In recent years, blended cements with partial replacement of mineral additives have drawn significant attention with their ability to conserve the available natural resources and also to reduce the effect of global warming produced by greenhouse gases. Composite Cement (CC) is a cement involved with maximum utilization of industrial wastes such as Fly Ash (FA) and Granulated Blast Furnace Slag (GBFS) in Ordinary Portland Cement (OPC) to develop low carbon binder and promoting the sustainable construction practice. In the present study, the share of OPC, FA and GBFS is optimized at 50%, 20% and 30% respectively by interblending these constituents in accordance with the IS 16415:2015 specifications. CC being a newly developed ternary blended cement, before putting this into construction practice, it is important to study the behaviour of CC in development of hydrates of cement which are responsible for the strength and performance of any concrete. The present study mainly focuses on the manifestation of phase changes involved in hydrates of cement with progressive curing and the same is studied using SEM, EDX, BSE, XRF and FT-IR techniques. The mechanical behaviour of CC mortars is compared with reference OPC mortars by correlating with microstructure analysis.

Along with commonly occurring Reinforced Concrete (RC) narrow normal beams, RC wide beams also find place in different kinds of structures. Wide beams have width to depth ratios more than one. The shear strength of normal RC beams with well distributed shear reinforcement along the span can be safely predicted by many national codes. But in wide beams, not only, the shear reinforcement demand has to be satisfied along the span, but also, across the beam width, adequate number of vertical legs have to be provided in each stirrup. Tests in this investigation were conducted on five RC wide beams; two beams had low shear stress, while three beams had high shear stress. The test specimens were 1700mm long, 250mm deep and 600mm wide. For all the beams the width to depth ratio was 2.4. In the two low shear stress beams, the stirrup legs varied from two to four. The three high shear stress beams HSB1, HSB2 and HSB3 had 2, 4 and 6 stirrup vertical legs respectively. In the two series of beams, the stirrups satisfy the requirements span wise and width wise. Exhaustive investigation, undertaken herein on wide beams, revealed several significant findings, for useful adoption by structural engineers. Among the many conclusions one is, for the realisation of design shear force, the spacing of stirrup legs across the width should be limited to lesser of effective depth and 300mm, for low shear stress, for beams with high shear stress, leg spacing should not exceed effective depth/2.

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Usage of Recycled Coarse Aggregate (RCA) in construction industry is the need of the era to achieve sustainability. To improve the performance of RCA, adhered mortar is removed by different physical and chemical treatments. This study investigates the practice of processed RCA in Self-Compacting Concrete (RCASCC) for replacement levels (0%, 25%, 50%, 75% and 100%) by abrasion for 500 and 1000 revolutions. The objective of the study is to optimize the number of revolutions and the replacement percentage of processed RCA in the mixes A and B. The study includes the mechanical parameters such as compression, split tension, flexure and bond strengths. Further, to understand and compare the stiffness behaviour of processed and unprocessed RCASCC, stress strain relationship is examined. From the findings it was observed that, with increase in the number of revolutions the performance of processed RCA is decreasing. Also, the results showed a relative improvement in performance of SCC mixes for 500 revolutions at 50% replacement level when compared to unprocessed RCASCC. The outcomes of the study facilitates an experimental evidence for the use of processed RCASCC in structural applications and fulfil the need of replace and reuse of construction demolition waste for achieving sustainability.

Fragility curve is a powerful tool in performance-based analysis to assess the seismic risk of the structural system. Many parameters like transitional damage states, plan asymmetry and different measures of seismic intensity and damage measures influence the fragility curves. It is essential to establish fragility diagrams for shear wall system where torsion is exhibited. In the present paper, the fragility diagrams of torsion imbalanced steel-concrete composite shear walls (CMSWs) building is developed. In current work, trapezoidal plan building frame-CMSWs structure is simulated to one fourth extents to substantiate analytical findings of modal and corner point’s characteristics with AZALEE shake table results of SMART 2008 project. Incremental Dynamic Analysis is conducted using a suite of fourteen real bi-directional orthogonal horizontal ground motion records. Further, fragility curves of composite shear wall building are compared using pre-defined damage thresholds of SMART 2008 project and HAZUS 2003 technical manual. Damage states of SMART 2008 have been derived for torsion induced Nuclear Power Plant building situated in France. While HAZUS defined limit states for common reinforced concrete buildings with shear walls situated in the United States. The damage states for asymmetric plan building with CMSWs are not prescribed by any seismic code. Hence, damage indices are established in the context of naturally generated incremental dynamic curves for the structural model to obtain more realistic results.

The present work aims to study the effect of light weight aggregates on structural performance of concrete. In this study, experiments were conducted to study modulus of elasticity, stress-strain behaviour, bond strength, flexure behaviour at different span to depth ratios on light weight and normal concrete specimens for appropriate comparison. For the tested specimens, significantly lower modulus of elasticity was observed for light weight concrete than normal concrete. Light weight concrete was found to be more brittle in nature i.e., the specimen failed rapidly after reaching peak stress. From the pull-out test, the bond strength of light weight concrete was found to be about same as that of normal concrete. For the both flexure dominated and shear dominated beams, significant difference was not observed between strength and stiffness of two types of concrete. The comparison between experimental and ACI 318-2019 theoretical short-term deflections showed that the equation gives lower values for both lightweight concrete and normal concrete beams. The work does not aim to arrive at generalized conclusions but to create confidence in engineering community for the promotion of structural grade light weight concrete and the scope of this study is limited to M40 grade concrete.

In order to develop full stress, rebar needs to be extended beyond a section for a length equal to development length in a reinforced concrete member. U-Hook or bent up bar is a solution to overcome the problem of development length, but congestion of reinforcement is an issue. Many a time, there will be shortfall, and mechanical anchorages or headed bars in place of hooks were used to overcome the congestion issue. An alternative method of anchorage with Helical End Rebar (HER) was investigated by conducting a pull-out test. HER may not fully address the issue of congestion. Parameters considered in the investigation are the diameter of the coil, pitch of coil and number of coils embedded in concrete. All these are combined as helix coefficient. It is found that the helix coefficient influences the anchorage of Helical End Rebar.

Standing Seam Metal Roofing (SSMR) systems have advantages of weather tightness, leak-proof performance, durability, and cost-effectiveness. Codification of SSMR designs is quite complex due to the interaction of several components. The design of supporting purlin is also difficult when the resistance from sheeting is accounted for. Since numerical models have limitations to capture this interaction, experiment based empirical equations are the only way to design these systems. Two types of profiles namely Flexlok® and Tracdek® profiles are widely used in practice. In the former, the roof sheets under upward wind depend on the clamping force between the sheet profile and a clamping device called a halter. The latter gets its strength from the integral folding of the sheet with the mechanical clamping device. Although these two systems have different load carrying mechanisms, the behavior of both has an impact on the secondary load carrying systems such as purlins. Unless this interaction of the sheeting and the secondary frame systems are experimentally evaluated, the design does not become rigorous. This paper presents experimental studies on the interaction behavior of two types of SS MR systems subjected to wind uplift. A special vacuum chamber is fabricated as per specifications in ASTM E1592 - 05(2017) for creating air-pressure differences. The various modes of failure in these two types of roof systems are captured in the experiments which will influence the overall behavior of the roof systems. The halter panel disengagement failure mode observed in Flexlok® panels and Tracdek® system undergo failure by the fracturing of sheets. During the interaction, the Flexlok® system experiences component failure, and hence its effect on the secondary frame is not significant. However, the Tracdek® system has a big influence on the interaction due to the larger restraints provided by the integral folding of clips with sheeting. The present design methods currently used to design the SSMR systems, underestimate the interaction effect in the Tracdek® system in which there will be a combined failure of purlins and the roofing sheets. However, purlins supporting flexlok system won’t fail since the sheet disengages early. The present experiments bring out the various failure modes and their failure load which are very essential for the codification of SSMR designs.

The postbuckling response of functionally graded hybrid composite plates subjected to combined uniaxial and in-plane shear loading conditions is numerically investigated in the present study. The finite element formulation-based software ABAQUS has been used for the numerical study. Eigen buckling analysis and Tsai-Hill failure criteria are used to determine critical buckling and first ply failure loads, respectively. Functionally graded composite plates with and without cutouts are considered for the study. Five different shapes and three different sizes of cutouts at the center of the plate have been taken to examine the response under the combined in-plane loads. Effect of (0/90)4s, (+45/-45)4s, and (+45/-45/0/90)2s fiber stacking sequences are also examined. It is shown that, diamond-shaped cutout of small size among the cutouts performs better in terms of buckling and first ply failure loads of the plates under compressive loads combined with negative in-plane shear load. The (+45/-45)4s stacking sequence has the highest buckling and failure loads in comparison to other layup sequences.

Parallel Kinematic Machines (PKMs) are widely used for precise applications to achieve complex motions and variable poses for the end effector tool. PKMs are found in several fields, including medical, assembly, and manufacturing, needing higher tracking accuracy. It is often desired to have a compact and simple architecture for the robotic mechanism. This paper explains the kinematic analysis of a 3-PPSS (P-Prismatic joint, S-Spherical joint) parallel manipulator with an equilateral mobile platform. The underlined joints indicate active joints. The forward and inverse kinematics for the proposed six Degrees of Freedom (DoF) mechanism is formulated using the Denavit-Hartenberg (DH) technique. A numerical algorithm is explained to solve the inverse kinematics for the mechanism. The Jacobian matrix has been derived for the mechanism considering its closed-form architecture. The Jacobian matrix is necessary to perform the singularity analysis and further determine the optimized dextrous workspace for the manipulator.

This paper investigates the buckling performance of FRP strengthened aluminium cylindrical airframe shells with initial geometric imperfections. This is studied for the shells with different r/t ratios undergoing different modes of buckling viz. elastic, transitional, and plastic. The difference in buckling response of FRP strengthened and corresponding bare metallic shells with variations in imperfection magnitude are brought out. This study demonstrates that 1) the elastically buckling shells display higher sensitivity to imperfection as compared to plastically buckling shells, and their buckling capacity and axial stiffness increase with FRP strengthening but decrease with increase in imperfection magnitude for both bare and FRP wrapped shells; 2) the transitional buckling shells display three distinct stages of buckling behavior with an increase in imperfection magnitude; and 3) higher number of FRP wraps stabilizes the metallic shell and leads to a uniform increase in buckling capacity at all values of imperfection.

The enthusiastic behaviour of people on structures can cause synchronized rhythmic movements which may lead to resonance between forcing frequency and one or more natural frequencies of the structure. Such a human-structure synchronization results in strong vibrations that affect structural stability and create discomfort among people. The Indian codes and standards do not consider Crowd-Structure Interaction (CSI), resulting in an unreliable vibration assessment of structures. The present work investigates the effect of CSI on the dynamic behaviour of pedestrian bridges in the vertical direction. The system is modelled as a two degree of freedom mass spring damper system and the modal properties are determined. The modal properties and response of the system are studied for varying crowd parameters such as size and location. A probabilistic sensitivity analysis is carried out to understand the sensitivity of modal properties and response of the CSI system to the parameters of crowd and empty structure, using a variance based method. Monte Carlo simulation is used to simulate samples of the random parameters. Crowd activity frequency and generated load factor are observed to be the most sensitive parameters affecting the vibration of the structure.

High performance Carbon Fibre Reinforced Plastic (CFRP) composites are widely used for launch vehicle and spacecraft structural applications. They offer the advantages such as high specific strength, specific stiffness and tailorability. Sandwich construction with CFRP skins and aluminium honeycomb core is extensively used for light weight construction. Embedment of plastic protective films in the CFRP skins is a potential failure mode that needs to be addressed in the composite manufacturing process as part of online quality control. In one of the launch vehicle components, a control coupon extracted from the parent CFRP sandwich structure failed at less than half the load compared to that of the remaining coupons. The failure was observed to be due to the presence of a plastic protective film in one of the skins. Ultrasonic through transmission testing, the primary Non-Destructive Testing (NDT) technique could not detect the embedment of the protective film. Due to this observation, the acceptance of an entire set of panels realised was in question. An alternate NDT method was required to confirm absence of such films in them. In this paper, the feasibility studies carried out and use of laser shearography technique in the clearance of the sandwich panels are presented. Comparison of test results on reference specimens using pulsed thermography is also presented.

Bolted joints are widely used in assembled structures. An introduction of a joint induces nonlinearity due to the presence of friction at interface. To understand the nonlinear characteristics of a bolted joint under dynamic loading, nonlinear parameters are identified based on equivalent single degree of freedom model of assembled beams with a joint. Subsequently, the governing equation is solved to obtain modulation equation using multiple scale method. Nonlinear analysis is done by analysing frequency response curves at different nonlinear parameters of bolted joint. The developed model can be used to identify bolted joint response with change in its preload.

In this study, short glass fibers with 1/4-inch average length and 16-μm diameter are uniformly dispersed into the epoxy system up to 3% volume fraction. Thus, prepared matrix system is used to fabricate 16 layered bidirectional glass fiber laminates by using hand layup technique and the effect of slender filler content on the mode-I fracture toughness of the laminated composites is investigated. Double cantilever beam specimens are machined from the cured laminates and fracture tests are performed under quasi-static loading conditions by following ASTM D5528-13 standards. Experiments suggest that filler reinforcement has marginal influence on the crack initiation toughness (GIi) of the laminates, however, the steady state and maximum energy release rates (GIc and GImax, respectively) are significantly improved in the case of filler reinforced laminates. The enhanced fracture characteristics due to reinforced fillers is attributed to the fiber bridging, short-fiber pull-out and crack branching.

In this study, concrete is modelled at meso-level (10-4 - 10 cm) where aggregates, mortar and/or the Interfacial Transition Zone (ITZ) are explicitly considered. Aggregates are generated based on a given aggregate gradation and then, those are placed randomly (uniform distribution) in the concrete domain. The remaining space of concrete domain is then filled with cement mortar. In this numerical concrete model, both cube (150 mm × 150 mm × 150 mm) and cylinder (diameter 100 mm × height 200 mm) specimen are modelled, and their behaviour is simulated under uniaxial compression at ambient as well as at higher temperature. The results are validated against corresponding available experimental results reported in the literature. The results indicate that meso scale model of concrete can automatically capture the effect of specimen shape on compressive strength of concrete, consider transient creep strain and help to identify both local and global failure pattern. Such meso-scale based approach makes the modelling more robust with explicit consideration of the effect of aggregate and mortar. Simulated results also show that different random configurations of aggregates have negligible effect on the homogenised compressive strength of concrete.

The research on an experimental investigation of fly ash-GGBS Based with high performance geopolymer concrete is done with an exclusive vision of not only to endeavor in the pursuit of reducing Global Warming on the earth and CO2 emission, but also for saving the earth from being affected by environmental pollution due to industrial waste. Geopolymer Concrete is used as an alternate for cement and M sand by a composition of Alkaline Activator Solutions (AAS) and Copper Slag (CS). To produce High Performance Geopolymer Concrete (HPGC), an experimental test was conducted by means of 11 (eleven) different mixing proportions with the replacement of binder material fly ash by Ground Granulated Blast of Furnace Slag (GGBS) with a proportion from 0% to 100% by weight at an increment of 10% with M sand as filler materials. Towards attaining the next stage of polymerization, Alkaline activator solutions (14 molar Sodium Hydroxide and Sodium Silicate) were used in this trail test and researched for polymerization. To adopt different mixing proportions, the specimen was cast and heat curing was done by maintaining 70 degree Celsius for 24 hours. The strength parameters of concrete such as compressive strength, split tensile strength and flexural strength were tested on the specimen. The test results show that the combination of 60% GGBS and 40% fly ash has produced high compressive strength of 71.70 N/mm2. Another trail test was made with the same proportion of binder material and the filler material of M sand is replaced with Copper slag from 0% to 100% by weight at an increment of 10%. By adopting eleven different mixing proportions, the result indicates that the substitution of 50% copper slag by M sand has yielded high compressive strength of 80.30 N/mm2. The HPGC has thus resulted by the above mixing combinations.

K-130, a Room temperature cyclotron building is one of the essential facilities in Variable Energy Cyclotron Centre (VECC), Kolkata, used mainly for research and development. Due to expansion of facilities a requirement was raised by the Radioactive Ion Beam Development Division (RIBD), VECC to test the electron Linac (e-Linac) injector in HR cave-1, which was the only shielded area for same machine. This in turn led to increase structural demand. Therefore, to facilitate the system and keeping the structural integrity intact, a demand reduction approach has been adopted without much changes in the dynamic properties of the structure. This paper brings out a retrofitting scheme with the introduction of composite beam concept in an existing structure to meet the demand of increase in superimposed dead load. Seismic feasibility of the structure has been concluded based on an indirect approach. Further, arrangements have also been shown to take care of the stress concentrations and ensure safe load transfer near cut-outs.

This study highlights the generation of truss-like patterns for Strut and Tie Modeling (STM) using bidirectional evolutionary topology optimization in concrete structures. STM is an effective approach for the design of Discontinuity regions (D-regions) where standard Bernoulli’s hypothesis cannot be applied. As the conventional methods of STM generally follow a trial and error procedure, the final solution may not be unique. Topology optimization is classified under structural optimization to find the effective layout of structure based on the load path method. It is a scientific method that relies on structural mechanics; the inaccuracies related to STM can be avoided with the aid of topology optimization. In static problems, minimizing compliance leads to reasonably more stiff structures. In free vibration problems, the maximization of eigen frequency can be taken as an objective to get the maximum stiff structure. Solid Isotropic Material with Penalization (SIMP) material model assumes a constant and isotropic material properties in each discretized rectangular element. Evolutionary optimization derives the optimum structural layout by removing the ineffective elements and adding the effective elements in subsequent iterations. Method of Moving Asymptotes (MMA) developed by Svanberg (1997) is a kind of convex approximation has also been implemented in static problems.

In most cases, the local failure of the connection in a steel framed structure affects the serviceability criteria of the entire structure. Hence, it is necessary to study and understand the behaviour and failure mechanisms of connections used in steel framed structures. In view of this, the paper describes the experimental, theoretical and numerical investigations conducted on the bolted moment end plate splice connection joining Hollow Tubular Sections (HTS). In this study, a four-bolt end plate connection configuration is adopted for the fabrication of splice connection, and also a parametric variation of the dimensional properties of the connection components such as thickness of end plate, diameter of bolt, and thickness of HTS member is considered. In the theoretical analysis, using the stub tee analogy method new design equations are predicted to compute the ultimate moment capacity of the proposed splice connection. In the numerical analysis, the behaviour of end plate splice connection (with the parametric variation) is studied using finite element package ANSYS in detail. Finally, a comparative study is done between the obtained results of theoretical, numerical with the experimental results to validate the accuracy of predicted design equations and the proposed numerical model.

Gusset plates are subjected to complex stresses and obtaining the design thickness is not straight forward as the stresses depend upon the thickness of gusset itself. In this study, a typical case of a corner gusset plate connected to tension member (bracing / diagonal) in a braced frame or a truss girder bridge is considered. It is assumed that the gusset plate is welded at the beam-column joint in a braced frame or at corner joint of a truss girder bridge and connected to the tension member by bolts in double row. Simple 2-D model of gusset plate is developed and non-linear finite element analysis is carried out with the help of ANSYS, a commercial finite element software, for varying load magnitudes. Four, six and eight bolt cases are analyzed. On performing several trails the required thickness of gusset to prevent net section rupture as per the non-linear analysis is noted based on the obtained von-Mises stresses and plastic strains for all the cases. Later the required thicknesses of gusset plates as per Whitmore’s theory and Indian, European, American and Canadian codes of practice are also calculated. Significant discrepancy was noted between the results of finite element analysis, Whitmore’s theory and the various codes of practice considered in this study. On examining the obtained results, probable design thicknesses of gusset plates are proposed for each case. The presented design thicknesses may be useful as a reference / guide for design engineers in fixing the initial thickness of gusset plate to prevent ‘net section rupture’.

This paper presents the study of design methods for checking of Reinforced Cement Concrete (RCC) circular columns crack width control. The various case studies of design explain the importance of crack width control in addition to design for limit state of collapse ie., strength requirements. In the beginning, this paper explains the cases for which the higher area of reinforcement is required for crack width control than the requirement for strength aspect. The sample design calculation for crack width checking is also presented. Next, this paper explains the safe zone in P-M interaction curve as per SP-16 of Indian standards, where the circular sections are safe in both strength as well as crack width control requirements. The unsafe zone in P-M interaction curve describes the circular sections are safe as per strength but unsafe as per crack width control requirements. Finally the method for modification of P-M interaction curve in unsafe zone is explained by increasing the percentage of reinforcement to satisfy the crack width control. The modified design charts for calculating area of reinforcement required are presented. These modified design charts provide guidance to the structural designer while designing for limit state of serviceability for RCC circular columns.

The paper deals with the experimental and theoretical results of elastic constants of polymer modified high strength concrete with high fibre volume fraction. To evaluate elastic properties of this composite system, compressive strength, flexural strength, shear strength and corresponding load deformation responses were examined experimentally. Elastic properties such as modulus of elasticity, shear modulus and Poisson’s ratio are first obtained based on experimental results. Simplified equations based on micromechanics, and solid mechanics theories are utilized for the evaluation of elastic properties of polymer modified randomly oriented short steel fibre reinforced high strength concrete. The micromechanics equations for the modulus of elasticity, the shear modulus and the Poisson’s ratio are based on the fibre volume fraction and the elastic moduli of the fibre and polymer modified concrete matrix. The existing empirical equations are also used to obtain elastic constants. These equations are applied in the full range of fiber volume fraction (1% to 10%). The comparison of experimental results with theoretical values shows the good agreement with each other. The novelty of the present paper is that the modulus of elasticity of this composite system is obtained experimentally using four point bending test and the Poisson’s ratio is obtained as a function of flexural and compressive strengths with sufficient accuracy.

Self-Compacting Concrete (SCC), is a highly workable material, compacted by its self weight without observable segregation and bleeding. In this study, Support Vector Machine (SVM) and particle swarm optimization based SVM models are employed to predict the 28 days compressive strength of individual SCC mix. A database of 62 no’s of SCC compressive strength from literature with cement partially replaced by fly ash is used for training the models. The test data consists of two groups, an individual study consisting of 9 datasets and other combination of three studies with 19 datasets tested separately. Similar input parameters from the train data is extended for testing the models prediction accuracy. Statistical parameters such as correlation coefficient, root mean square error and scatter index are used to evaluate the models’ prediction results. The particle swarm optimization based SVM model is capable of selecting appropriate SVM parameters to increase the prediction accuracy. From the results, it is seen that both SVM and particle swarm optimized SVM models have good capability in predicting the SCC compressive strength.

The complexity in modeling Un-Reinforced Masonry (URM) buildings to understand their behaviour under seismic loading has been recognised in literature. The main objective of this study is to identify a methodology for quantification of seismic safety of URM building through incremental dynamic analysis. Prathmic Swasthya Kendra a single storey hospital building constructed in 1960 located at Uttarakhand, India, has been considered for this study. In the present study, equivalent frame modeling procedure for URM building has been adopted. User-defined shear hinge and flexural hinge properties are developed and are used in the analysis. Fragility curves are developed for the URM building from the incremental dynamic analysis, wherein, uncertainty in the characteristics of earthquake time histories are accounted by the use of suite of far-field ground motions. Fragility curves for different performance levels similar to that of. Immediate Occupancy (IO), Life Safety (LS) and Collapse Prevention (CP) as specified in FEMA 356 (2000) have been developed and collapse margin ratio is estimated. Adjusted Collapse Margin Ratio (ACMR) has been evaluated and comparisons are made with the minimum acceptance criteria specified for collapse limit state. As a part of the methodology, response reduction factor (R) is obtained for the URM building and the comparison has been made with the respective specification for URM building specified in Indian seismic standard. The methodology proposed can be adopted for seismic safety evaluation of existing or new URM buildings.

The seismic crack propagation in a typical Zoned Roller Compacted Concrete (ZRCC) gravity dam is modeled and analyzed by using extended finite element method (XFEM). The cracking process of Koyna dam due to 1967 Koyna earthquake is carried out considering the dam-reservoir-foundation interaction for validation of modeling process. Zoned Roller Compacted Concrete (ZRCC) gravity dam, viz., Gibe-III dam is considered to be a case study for the seismic crack propagation analysis. The dam is analyzed with different initial cracks at selected positions of the chosen ZRCC gravity dam by considering rigid and flexible foundation conditions. The effect of initial crack location on the crack propagation mechanism due to the seismic reaction is observed.

The paper investigates the behaviour of diagrid structures in comparison to conventional framed structures when subjected to earthquake ground motions. The work involves experimental study using a uniaxial shake table, on models fabricated in the laboratory, and numerical simulations of the same in ETABS. Scaled-down models of a four-storey structure mimicking a conventional framed building and a diagrid building are used and linear time history analyses for different earthquake ground motion are performed. The results of the experimental studies indicate that the diagrid model performs in a better way compared to the conventional framed structure in terms of storey drifts, top storey accelerations and displacements. Substantial reduction in the top storey displacement is observed by employing diagrids. A pushover analysis performed towards the end shows the necessity to conduct nonlinear analysis to ensure the stability and ductility of the diagrid structure.

An experimental study on the sensitivity of the Acoustic Emissions (AE) to the stress field and steel reinforcement in concrete beams is reported in this article. The Reinforced Concrete (RC) beam specimens were tested under a monotonically increasing load in the laboratory. Three large RC beams with shear reinforcement and another two large RC beams without shear reinforcement were tested. The aim is to study the sensitivity of the AE to the stress field and the steel reinforcement. Gaussian Mixture Modelling (GMM) algorithm of AE was implemented for the crack classification in the RC beams. Further, sifted b-values were used to improve the interpretation of the conventional b-value analysis. AE generated during tensile cracking and shear cracking were compared with the AE based sifted b-values for RC beams with shear reinforcement and RC beams without shear reinforcement. The AE based sifted b-values, which reflects the extent of the fracture process, decreased with the increase in mid-span deflection. When the generation of AE related to tensile cracks was less, the sifted b-values decreased gradually. In the shear failure beam, the AE related to shear cracks constituted a higher percentage of total hits, and sifted b-values sharply decreased. The observations may provide a reference for the studies related to AE testing of RC structural members.

A non-linear static pushdown analysis was used to evaluate the progressive collapse potential of all-steel Buckling Restrained Braced (BRB) frames. The frames were modelled using alternate path method in SAP2000®. In framed structures, adequate lateral resistance can be provided with steel braces. But, in seismic areas, these tend to buckle and exhibit reduced strength, stiffness, and resistance under periodic loading. All-steel BRBs are excellent in dissipating energy due to their high stiffness and ductility with reduced cross-sectional area. In this paper, a comparative study was performed to evaluate the improvement in energy dissipation of frames with ordinary concentric steel bracing and all-steel BRB. Firstly, frames with two different types of all-steel BRB obtained from literature were compared. Secondly, the effectiveness of all-steel buckling restrained braced frames under three bracing patterns, namely, double X, inverted V and hexa-bracing patterns were investigated. The progressive collapse potential was estimated from the variation of vertical deflection with the percentage of load. The ductility and support rotations were then determined from the estimated progressive collapse potential. These were then used as acceptance criteria for investigating progressive collapse as per General Service Administration (GSA) specifications.

In the present study, investigation on mechanical properties of effect of grading of aggregate, size of fly ash and polymer content on Polymer Concrete (PC) with fly ash as fillers was conducted. The polymer-based concretes were also exposed to elevated temperatures and tested to study the change in its mechanical behavior. The mechanical properties, i.e., compressive strength, split tensile strength, flexural strength, stress-strain behavior and modulus of elasticity of PCs and Ordinary Cement Concrete (OCC) were determined. The polymer and fly ash content were kept between 12.4%-13.2% and 7.6%-9.6%, respectively. The results obtained show that the PC possess significantly higher mechanical strength as compared to the respective OCC. Also, the polymer and fly ash content have to be controlled properly in order to achieve higher strength. The mechanical properties of PC depend on grading of aggregate and particle size of fly ash. The mechanical properties of PC exposed to elevated temperatures show satisfactory behavior up to 240°C, beyond which it decreases significantly.

There is a pressing need for an alternate solution for the natural fine aggregate in the construction industry since the availability of natural resources is decreasing tremendously due to urbanization and industrialization. On the other hand, increased waste generation enormously, the disposal of the industrial waste efficiently and economically is another big task. Therefore, utilization of industrial by-product in concrete is not only a method to dispose the industrial waste but also enhances the construction industry. In this paper, we discuss in detail the possibilities of utilizing copper slag, a by product obtained during the smelting and refining of copper as an alternative for manufactured sand as fine aggregate in reinforced cement concrete through systematic evaluation of physical, mechanical and chemical properties. Various mix designs of M25 and m30 are prepared and the fine aggregate is replaced with copper slag in different proportions and conducted the strength tests. Nondestructive tests, durability tests, and compositional analysis (SEM-EDAX). The results suggest that copper slag can indeed be used as a fine aggregate replacement for manufactured sand reinforced cement concrete, without compromising on the quality, thereby contributing to the direction of environment friendly building materials with economic benefits, which is the need of the hour.

This paper aims to illustrate the influence of Brick Masonry Infill (BMI) in reinforced concrete (RCC) building-composite shear walls dual system using the capacity spectrum method. The capacity spectrum method captures the unpredictability and ambiguity related to capacity spectrum properties, damage states, and characteristics of ground motion. Spectral displacement-based fragility curves and damage probability matrices subjected to different damage states are generated for the bare frame, frame with only BMI and frame-steel concrete composite shear walls (SCCMSWs) system with BMI. From the comparative study of the damage probability matrices, it is concluded that frames with BMI and SCCMSWs have shown better performance during the action of the lateral load.

In the present experimentation, Fibrous Self-Compacting Concrete (FSCC) using mixed fibers (steel and glass, steel, and polypropylene) have been studied for its mechanical properties. It is attempted to know the effect of fiber percentage as well as the aspect ratios of steel fibers in various combinations. The aspect ratios of steel fibers tried were 20,30 and 40. Total fiber percentages adopted were 0.2, 0.4,0.6 and 0.8. Glass and polypropylene fibers have constant aspect ratios. By this, the smooth, uninterrupted flow of fibrous Self-Compacting Concrete (SCC) was obtained. The extent to which these fibers improve the mechanical properties of SCC is studied. Mineral admixtures of flyash and Condensed Silica Fume (CSF) were employed at 20% and 10% respectively as replacement of Ordinary Portland Cement (OPC) for additional beneficial properties. This investigation brings out the influence of mixed fibers at different percentages with different aspect ratios of steel fiber on the structural properties of SCC. The admission of fiber at a certain percentage contributes towards more compressive strength. A combination of glass with steel fiber contributed better tensile strength and flexural strength compared to polypropylene with steel fibers.

This paper assesses the current local buckling requirements of carbon cold-formed steel hollow sections under axial compression, using data from literature. A total of 39 Circular Hollow Steel Sections (CHSS s) are analysed, and these include 19 columns of mild steel and 20 columns of high strength steel. Variables in the study includes the length, diameter, thickness and material properties. The outside diameter-to-thickness ratio (d/t) for CHSS s of mild steel ranged from 48.72 to 249.23, while the outside diameter-to-thickness ratio (d/t) for CHSS s of high strength steel ranged from 16.15 to 46.84. The corresponding yield stress for mild steel ranged from 203.80 MPa to 622.80 MPa, while that of high strength steel ranged from 1341.00 MPa to 1405.00 MPa. A comparison with CAN/CSA-S16-09 and EN 1993-1-1, shows the limits of both standards to be too conservative. New slenderness limits are proposed to improve the design of these sections.

This research entails the analysis of Taguchi optimization for AISI 1045 steel considering tool life and surface roughness as the noise factors. The research investigation has been used to optimize the cutting parameters such as depth of cut, cutting speed and feed rate affecting the performance characteristics of the cutting tool used for turning operation. The L9 orthogonal array, Signal to Noise (S/N) ratio and analysis of variance (ANOVA) were used during the optimization process of the turning operation using a tungsten-carbide cutting tool. Furthermore, a confirmation test has also been performed to estimate the improvement of the noise factors such as tool life had an increase by 190% and decrease of surface roughness by 40%.

A typical petrochemical complex consists of various components of different complexities such as structures of various proportions, critical piping, tanks and massive compressors. The consequences of a seismic event in a process plant is severe compared to conventional civil structures considering that damage to even a single component would result in release of toxic gases and lead to an interruption in the production causing economical losses and threat to society and environment. Pipe rack structures with the supported piping systems represents an important item in petrochemical complexes, refineries and LNG plants as they run in kilometres of length connecting various process units in the complex. The seismic hazard posed by such structures is evident in that they carry piping systems with hazardous fluids and support other critical equipments such as air coolers and exchangers. The paper presents the seismic fragility assessment for a typical steel pipe-rack structure adapted from a petrochemical complex built in a region of moderate seismicity. Pipe rack structure is first verified for its capacity as per the European codes. The Incremental Dynamic Analysis (IDA) is then performed to obtain an insight into the dynamic response of the structural system in both the transverse and longitudinal directions. The fragility curves developed for different performance levels based on the IDA data are used for the seismic assessment.

Even though there are extensive studies conducted on the mineral admixtures to control chloride permeability, the very few studies were conducted in India on the usage of corrosion inhibitors in concrete in order to delay the corrosion process. The results of the laboratory studies conducted using two commercially available corrosion inhibitors to determine the effectiveness and their influence on strength and durability parameters of Portland cement concrete are presented in this paper. This study examined the workability, compressive strength, split tensile strength, flexural strengthdevelopment in concretes mixed with anodic inhibitor (calcium nitrite based) and bipolar corrosion inhibitor (amino alcohol based). The durability tests such as the Rapid Chloride Permeability Test (RCPT) and Water Permeability Tests (WPT) are also conducted to determine the effectiveness of inhibitors.Test results showed that addition of calcium nitrite based inhibitor has resulted in marginal increase of compressive strength of concrete at 28 days, whereas, the addition of bipolar inhibitor has resulted in marginal decrease of compressive strength of concrete at 28 days. Addition of both the inhibitors has improved the split tensile strength but reduced the flexural strength. The resistance to the penetration of chloride ions of concrete is marginally improved by adding both the inhibitors. Water permeability resistance was improved by adding both the inhibitors at 5% dosage.

Monitoring of the large structural systems for purposes of assessing the potential degradation of structural properties by identifying the dynamic characteristics is needed for assuring the safety of the system. Measurements made at a single point in the structure can be used to detect, locate and quantify the damage. In this work, a method for determining the damping characteristics and identifying the presence, location and severity of structural damage by observing the potential degradation of modal characteristics is presented. This method uses the dynamic properties obtained from the vibration response of the structure both in damaged and undamaged conditions. A three-storied aluminium base frame and 8 damage induced frames were experimentally studied by horizontal shake table. The damage was induced in the base frame by reducing the cross-section of the column. The experimental observations in terms of frequency, displacement and acceleration were used to obtain the dynamic characteristics of the structure. By comparing both theoretical and experimental results of the storey level deflection, the damping ratio of the structure is identified. The identified damping ratio corresponding to each frame is used in the damage assessment algorithm. This algorithm gives reduced storey level stiffness of the structure. The characteristics of the damage in 8 damage induced frames are identified from the results. The method is verified by comparing obtained reduced stiffness with manually calculated stiffness value. The reduction in the stiffness of each storey reflects the location of the damaged column. The analytical results show that the presented method can lead to satisfactory results in most cases.

Boundary conditions are one of the key parameters that have a significant effect on postbuckling response. In the current paper, flexural and in-plane boundary conditions are considered to study their effects on buckling and postbuckling responses of functionally graded hybrid plate with and without cutouts subjected to positive and negative in-plane shear loads. The quasi-isotropic (±45/0/90)2s layup sequence is considered in the plate for the numerical investigation with various shaped cutouts. The flexural boundary conditions include all four edges simply supported, two edges simply supported, and two edges clamped, and all four edges clamped while the in-plane boundary conditions are simply supported on all edges with different in-plane boundary restraints. The analysis is based on finite element method-based software ABAQUS. Postbuckling strength is predicted by non-linear analysis static-riks method in which geometric imperfections are incorporated and the first failure is predicted by Tsai-Hill failure criterion. The effect of flexural and in-plane boundary conditions on postbuckling strength of composite plates is explained distinctly. Buckling and postbuckling strengths are observed to be higher in plates with all edges clamped while it is lower in case of plates with all edges simply supported in case of flexural boundary conditions. PBC1 in-plane boundary restraint is having high buckling and postbuckling strengths amidst all in-plane boundary conditions. Though plates without cutout have higher buckling capacity, it is worth noting that functionally graded hybrid composite plate with diamond shaped cutout can resist higher in-plane shear buckling load than other shaped cutouts for both flexural and in-plane boundary conditions.

A structure subjected to operational dynamic loads or moderate levels of ground shaking is expected to remain elastic. However under severe earthquakes, which are not very frequent, the same structure is designed to exhibit inelastic behaviour and sustain some damage so as to achieve an economical design. This dual strategy of seismic design makes understanding of elastic as well as inelastic behaviour of structures important. The present study devises an algorithm to assess effects of soil-structure interaction on elastic and inelastic seismic response of structures with kinematic hardening using the substructure approach. The critical step involved in this approach is the determination of dynamic impedance functions. The dynamic impedance functions have been obtained from literature. Wherever required, plots in Gazetas (1991) have been digitized to obtain polynomial expressions. The dynamic analyses on SDOF idealizations of structures have been performed in MATLAB using Newmark γ-β method. Effects of few engineering design parameters, which encompass material and geometrical properties of a soil-structure system, on the structural response of SSI systems have also been explored. The present study is restricted to moment resisting framed reinforced concrete buildings founded on embedded raft foundations.

The prediction of shear strength of RC walls by various empirical, semi-empirical and code equations is highly deviating. The accuracy of such predictions is a great concern for the designers. Such deviation in the prediction needs to be addressed. Several predicting equations proposed and reported prominently in various sources have been assessed through statistically based 333 selective experimental data points. The box and whisker plot has been developed for the scatter of the ratio of predicted-to-measured ultimate shear strength for all the predictive equations. The deviation of the predicted shear strength of RC walls as per the existing equations has been inferred. The prediction of the shear strength of RC shear wall by very few equations are in close proximity with the statistical experimental data. Though several factors influence the shear strength of RC walls, the role of vertical and horizontal reinforcement, axial load, and boundary elements is still debatable. The selective main factors influencing the shear strength of RC walls have been emphasised. The refined predictive model has been described from the assessment of the data in terms of influencing factors on the shear strength and behaviour of RC shear wall. The best predictions have been validated with the popularly accepted experimental results.

This paper presents the results of experimental studies conducted on a small-scale model of a shear building subjected to ground motions. Performance of a Tuned Mass Damper (TMD) as a linear Dynamic Vibration Absorber (DVA) and a track Nonlinear Energy Sink (NES) as a nonlinear DVA are compared considering their effectiveness when employed in this model. Experimentation is carried out in a uniaxial shake table for 32 different earthquake ground motion time histories. The results show that the track NEShas a versatile nature in response control and is inherently stable, whereas the TMD in the presented form lacks versatility and has stability issues. As far as the reverse flow of energy from the DVA to the primary structure is concerned, track NESshowed better performance. The study also reveals that TMDhas a high potential as a vibration control device to reduce the maximum response.

In a precast concrete wall type building, the joints between the precast wall panels are critical interfaces of force transfer. This paper investigates the influence of modelling the grouted vertical joints (considered to be emulative joints) between the wall panels on the behaviour of a building under lateral loads. To quantify the influence, three different types of models were investigated (i) monolithic model without considering the joints, (ii) walls with gaps for the joints and (iii) walls with shear link: elements for the joints. Next, two different modelling approaches were considered: (i) reference models using two-dimensional (2D) membrane elements and (ii) simplified models using one-dimensional (1D) equivalent column elements. Nonlinear static pushover analysis was carried out on standalone wall panel assemblages (with and without openings) and on a typical midrise building. To capture the material nonlinearity under increasing roof displacement (drift), multi-layered membrane elements and point plasticity in the column elements were used for the two types of models, respectively. From the observed results, it was found that a model with gaps for the joints gives an overestimation of drift and conservative estimation of lateral strength compared to the model with link elements. Also, it was observed that the behaviour of a wall panel assemblage modelled using column elements was comparable to that of a model using membrane elements till the peak strength, with acceptable variation in the post-peak behaviour. Hence, it can be inferred that a model using column elements for the panels and link elements for the joints as demonstrated in this paper, is suitable for the pushover analysis of large buildings made of precast wall panels.

Underground metro stations are susceptible to the significant external loads such as earth pressure, water pressure, bedding stiffness and backfill soil cover. The ground imposes formidable challenges in design due to geological complexities, ground water, induced stresses, geological formation history etc. At the initial phase of project, the design is carried based on the available limited geotechnical information. However, further analysed and modified based on the detailed investigation. Hence, it is important to study the influence of earth pressure coefficient at rest (ko), Ground Water Level (GWL) and bedding coefficient (ks) on the design of underground metro stations to establish graphical interaction. The paper presents a parametric soil structure investigation for shallow cut and cover underground metro station having soil cover of minimum 2m on roof. The wide range covers most of the geotechnical conditions across cities in India. 3D Finite element models are analysed considering variation in governing loads and design bending moments at about 20 key locations are presented graphically. The study includes wide range of 132 non-linear 3-D finite element structural models. The sensitivity analysis benefits for optimisation, reducing risk due to uncertainties and to develop the preliminary structural analysis with respect to lower bound and upper bound parameters.

Shear failure in a reinforced concrete beam is a sudden failure which is associated with crushing of concrete and is a brittle failure. A structural designer should be aware of various components of shear resisting mechanisms particularly the shear resistance of concrete. In this regard, an experimental investigation was carried out on forty simply supported reinforced concrete beams, to examine their shear performance of with and without shear reinforcement. This paper reports the results of a laboratory based experimental study aimed at studying shear performance of blended concrete beams with fly ash and recycled aggregates. Blended concrete beams of M35 and M45 grades were produced by partially replacing the cement by 25 percent fly ash and the Natural Coarse Aggregates (NCA) were replaced by Recycled Coarse Aggregates (RCA) in different fractions of 0,25,50,75 and 100 percentages. The experimental shear strength of blended concrete beams was then compared with predicted shear strength evaluated from various international codes and some existing empirical models in order to adjudicate the relevance of the experimental shear strength with the predicted shear strengths for beams without shear reinforcement.

This study presents the synergistic effects of polymer and steel fibres on high strength concrete. The various physical/mechanical properties considered in this study are workability, compressive strength, flexural strength, shear strength and toughness. The reference mix having strength of 50.96 MPa is used throughout the study. The dosages of SBR latex (polymer) are varied as 5%, 10% and 15% by weight of cement and steel fibre content varied from 1% to 10% by weight of cement at the interval of 1%. Two curing regimes were considered in this investigation. Standard cubes of size 150mm, prisms of size 150  150  700mm, push-off specimens of size 150  150  450mm for single shear were prepared. A comprehensive casting and testing program was carried out with 324 specimens for 28 days. The workability of fresh concrete is found to be increased with addition of polymer in fibre reinforced concrete. The significant improvement in various strengths and toughnesses is achieved compared to the reference concrete.

A study on simply supported single-cell skew reinforced concrete box-girder bridge is presented herein. The analysis is carried out using a finite element based software SAP 2000 v.14.0.0. An existing model is considered first to validate the present results with the reported one. A convergence study is then performed for the model, considered for investigation, to decide the mesh size for ensuring reliable results. Total 64 models, subjected to dead load and IRC class-A wheel load, are considered for investigation. An exhaustive parametric study is carried out in which the maximum bending moment, maximum shear force, maximum torsional moment, and reactions in girders are calculated. Further, stresses and vertical deflection of bridges are calculated. The results are presented in the form of force ratios between the skew bridge and the straight bridge. The skew angle effect, up to 30°, is almost negligible on forces and deflections, and thus such bridges can be analyzed as a straight one. The influence of other factors like span, span to depth ratio, and girder spacing are also considered for investigation. The results obtained in the syudy may be useful to the design of skew box-girder bridges.

This paper deals with nonlinear analysis of slender steel I-girders as well as horizontally curved slender steel I-girders under normal conditions and elevated temperature conditions. Under normal conditions, the effects of temperature on the analysis were neglected and under elevated temperature conditions, the temperature varies gradually from 0°C to 800°C. Three different girders, one straight and two curved girders, were modelled using the ABAQUS software. Effect of slenderness ratio and radius (for horizontally curved girders) were studied for 30m long slender I-girders as well as 30m long slender horizontally curved I-girders under normal conditions and elevated temperature conditions. It was found that slenderness ratio affects the axial force in the straight girders but does not have any significant influence on mid-span deflections at elevated temperature. For horizontally curved girder, the effect of angle subtended by the whole girder at the centre (radius of curvature) does not seem to have any significance for gradually elevated temperature. When temperature reduces from 800°C (i.e. cooling) to 0°C, a significant reduction in mid-span deflection was observed for straight girders but no significant reduction in mid-span deflection of curved girders was found. Finally, it can be concluded that horizontally curved girders are badly affected by elevated temperature compared to straight girders.

In this paper, the study of the buckling modes and the effective length of bars in steel welded space frames has been carried out experimentally and numerically using FEM based software. A 3D model of the under-slung bridge has been used for the experimental and numerical study. The bridge model has been designed in such a way that buckling takes place in the top chords. Effective length for each buckling bar is obtained by experimentation and comparison has been done with simulated results. For the calculation of effective length using simulated results, the distance between the points of contra-flexure has been used. This study provides an insight into the significant variations in the buckling behaviour of the frame members with the change in the buckling modes and with the change in the size of the members connected with the buckling member.

In the Yangtze Basin and southern China, there are a large number of rural buildings with rowlock wall. Because China is an earthquake-prone country, the application and strengthening of rowlock wall houses in earthquake region is a critical issue. However, strengthening of rowlock wall house is lack of a clear code or specification. This study presents the cyclic loading test of four rowlock walls with different strengthening details. The test results demonstrate the damaged rowlock walls can restore their original ultimate bearing capacity; it is also indicated that the use of cracking mending with steel mesh mortar covering repaired the walls improves the seismic behavior of the rowlock wall.

Pond ash is byproduct of thermal power station which is generated due to deposition of felled fly ash and bottom ash in large ponds. This paper discusses the development of Fuzzy Multiple Criteria Decision Making (FMCDM) model for estimation of Optimum Percentage of Pond Ash in Concrete (OPPAC). An every year huge amount of ash remains unutilized and dumped in ash ponds. Its leads to different types of pollutions like air pollution, water pollution and land pollution. One of the effective ways to utilize this waste is to replace cement partially with pond ash and to achieve sustainability in concrete construction. Here, a fuzzy model is developed to use appropriate percentage of pond ash in concrete. The fuzzy technique used in present study, estimates the optimum percentage of pond ash in concrete, taking into consideration the concrete performance parameters i.e. Workability, compressive strength, physical properties, chemical properties and setting time and not only compressive strength.

Alkali Activated High Performance Concrete (AHPC) is an innovative concrete that belongs to the spectrum of alkali activated materials. AHPC uses the concept of involving two different domain of concretes such as Alkali Activated Slag Concrete (AASC) and High Performance Concrete (HPC) in a right manner to obtain sustainable HPC. In the current study, Ground Granulated Blast furnace Slag (GGBS) is used as full replacement to Ordinary Portland Cement (OPC). GGBS is a byproduct obtained from iron-steel making industries. This binder contains silicates and aluminates, which acts as a precursor to AHPC. This study aims to optimize the different parameters like GGBS content (500, 550, and 600kg/m3), Silica Fume (SF) content (10, 15, and 20% of GGBS), and Quartz Powder (QP) content (10, 15, and 20% of GGBS) to obtain AHPC using Taguchi method of design of experiments. Further, to optimize different mixture proportion, Desirability Function Approach (DFA), Grey Relational Analysis (GRA), and Technique for an Order of Preference by Similarity to Ideal Solution (TOPSIS) were adopted. Results show that AHPC mixtures can produce 28 days compressive strength in the range of 91-107 MPa with flow value of around 150-170mm.

The Non-Structural Components (NSCs) of the structures require more awareness for seismic design so that it not only save the life but also minimise the economic loss. For the design of NSCs, the acceleration amplification factor is important, which is observed by inertia force exist in the building. Previous researchers worked in the field of amplification factor for higher hazard level and proposed that the amplification factor depends only on normalising height (ratio between height of the floor to total height of the building concerning base) and fundamental period of the structures for any peak ground motion, but it is found to be unsafe. However very few have paid attention to low to moderate hazard level. Even a low peak ground acceleration may amplify the strong acceleration significantly. In this paper, the peak horizontal floor acceleration of NSCs for low to moderate hazard level have been obtained. For this 2,4,6,8 and 10 stories moment-resisting RC frame models with low to moderate hazard level (0.01g-0.31g) have been considered. For the analysis 32 ground motion data in the range of 0.01g to 0.1g, 29 ground motion data in the range of 0.1g to 0.2g and 31 data in the range of 0.2g to 0.31g are considered using linear time history method. Based on analysis results, mathematical models are proposed to determine the absolute acceleration amplification factor. On comparison to other models it could be found that proposed mathematical models predict realistic values of acceleration for the safe design of NSCs.

Finite Element Method (FEM) of analysis is a very powerful computational tool. The objective of the paper is to summarize the theory and the associated programming algorithms developed for a 3 dimensional, 8 noded brick element employing isoparametric formulation. The dynamic elasto-plastic analysis is required for analysis of special problems in civil engineering like analyzing the effects of collision due to a vehicle or an errant ship on bridge structure, application of a moving force like wheels of a loaded truck moving on the deck. A set of connected subroutines were developed to investigate concrete bridge piers subjected to collision loads. The developed subroutines can also be employed to investigate the elasto-plasticity induced in concrete subjected to any dynamic load, with a few modifications as required by the user. The programs are validated using ANSYS software with acceptable difference in the results. An attempt is made to document a systematic algorithm of the programs developed to solve the problem of material non-linearity in concrete coupled with dynamic analysis using a three dimensional element.

This study focuses on the effect of corrosion in concrete due to change in parameters like w/c ratio, cover depth and reinforcement diameter. For this an experimental approach is carried out in laboratory where accelerated corrosion in the concrete was introduced by impressed current technique. In order to quantify the amount of corrosion occurred in concrete beams half cell potential method was used. Various results and patterns observed in this study is tabulated and thoroughly discussed in successive chapters. In order to find the change in mechanical strength in concrete due to corrosion flexural strength of beams were determined using center point loading method. Faraday’s law is used to find theoretical mass loss in reinforcement due to corrosion and results were compared with that obtained from experimental investigation. For the purpose of experimental investigation two different types of additives were added during casting of concrete. Firstly ultra fine slag Alccofine-1203 is used as partial replacement of cement. Addition of alccofine increases the packing density of concrete thus making concrete less permeable and due to which concrete becomes resistant to corrosion. Other additive used in this research work is crimped steel fibers 1% by weight of volume fraction of concrete as per previous literatures. Addition of steel fibers hinders the electrochemical process at reinforcement surface by reducing the availability of water and oxygen. Different sets of combinations of theses additives were used and tested in laboratory to observe their effect in hardened concrete to counter corrosion.

Recycling and reuse of waste products are required for achieving sustainable development in construction sector. In order to meet the growing demand for fine aggregates, numerous research studies have already been reported in literatures on the feasibility of using several industrial byproducts such as copper slag and waste foundry sand as partial replacement material for conventional fine aggregates, and promising results have been obtained. In this research, an attempt is made to use Recycled Plastic Wastes (RPW) obtained by recycling only plastic carry bag wastes as fine aggregates in cement concrete production. Different percentages of untreated and chemically treated RPW fine aggregates were used to replace conventional fine aggregates, and the properties of concrete such as compressive strength, flexural strength and splitting tensile strength were determined. Scanning Electron Microscopy (SEM) images were obtained from the tested samples of concrete. The quality of concrete with RPW fine aggregates was determined using Ultrasonic Pulse Velocity (UPV) method and compared with that of control concrete. The test results showed that concrete with treated RPW fine aggregates achieved higher strength than the concrete with untreated RPW fine aggregates. Concrete with strength up to 80% of control concrete could be achieved by using 10% of treated RPW fine aggregates for replacing conventional fine aggregates. The quality grading of concrete based on UPV tests was “excellent” or “good” for all levels of replacement considered in the present study. Equations based on regression analysis were proposed to predict the flexural and splitting tensile strength of concrete with untreated and treated RPW fine aggregates.

The idealization of support conditions for the hyperbolic cooling tower shell has significant influence on the free vibration response of the shell. Although considerable research is available in the literature regarding the behavior of the shell under different support conditions independently, the comparative study of different idealizations of support conditions on free vibration response of tower shell is the objective of the current study. Most of the researchers considered the pinned support or the fixed support for the shell and inferred that these idealizations adequately represent the free vibration response of the shell supported on columns. However, the current study indicates that the natural frequencies of the column supported shell is closer to the fixed/pinned idealization with the variation of 6-10% for the initial few modes only and vary to 40-50% in the higher modes.

In present study, seismic fragility curves are developed for a typical pile supported wharf, for some important port sites in Gujarat i.e. Mundra, Kandla, Navlakhi, Dahej and Hazira, thereby representing highest and moderate level of seismic zones of India (Zone V and III). Curves are developed for three levels of ground shaking i.e. Serviceability Earthquake (SE, 72 years return period), Design Based Earthquake (DBE, 475 years return period) and Maximum Considered Earthquake (MCE, 2475 years return period). The structural model of wharf is prepared in SAP 2000 using Winkler model to represent soil pile system. Pushover analysis is performed to obtain the capacity curve of wharf. Damage states - serviceable, repairable, near collapse and collapse; are established as per PIANC. Site specific spectra is constructed using geotechnical report of port sites with reference to ASCE7-05 and correspondingly 5 pairs of seismic events are selected, normalized and scaled to 0.1g, 0.2g,…1.0g to represent demand. Using Capacity Spectrum Method, maximum displacements at deck are obtained and response matrix is created. Based on the damage states and the response matrix, the fragility curves of the wharf are constructed. It is revealed that port sites Mundra, Kandla and Navlakhi are most susceptible to seismic risk, while Dahej and Hazira are comparatively at lower risk. Further, the specified spectra given in Indian standard underestimates the ground motions, particularly in zone V. Hence, site specific spectrum is essential for seismic design of port structures. At the same time a need is felt to strongly revise the Indian standard.

In present study, effect of micro carbon fibers on strain sensing property and structural behaviour of the reinforced concrete (RC) beams in absence of stirrups was experimentally investigated. A total of three RC beams of medium scale having dimensions of 125mm width, 350mm height and 1500 mm long were constructed without stirrups. All the three beams had different longitudinal reinforcement ratios (0.92%, 1.03% and 1.43%). All the beams had Carbon Fiber Based Concrete (CFBC) at top and bottom surface of the beam in mid span for a length of 350mm and depth of 78 mm. All the beams were tested to failure under four point bending test for evaluating strain sensing property and structural behaviour of Carbon fiber based concrete. Fractional Change in Resistance (FCR) was calculated for top and bottom surface of beam that had carbon fibers and co-relation between FCR of CFBC, concrete strain and strain in tensile reinforcement is plotted. It was observed that as load increases on the beam the FCR was increasing for bottom surface (tensile surface) and decreasing for top surface (compressive side). The trend of change in FCR for top and bottom surface is observed to be same as strain in tensile reinforcement and concrete changes respectively. It was also observed that this FCR can be used for strain and damage detection in beam as a NDT health monitoring approach. Further electrical properties and structural behaviour of all the beams is explained in detail.

Tall buildings are being constructed across the globe at an ever-increasing rate. The main reason for this is increasing population and paucity of land. Structural design of high-rise buildings is mainly governed by lateral loads due to wind or earthquake. Wind and earthquake loads are uncertain and random in nature. It is difficult to predict them correctly. Loadings on high-rise structures are different from low rise structures. Wind load is a major concern to high-rise structures, which not only causes vibration but may bring fatigue problems as well. To address this issue, in this paper an attempt is made to use, the equivalent structural stress method for the fatigue life assessment of a diagrid high-rise steel structure. Extended 3D Analysis of Building System (ETABS) 2017 software is used for modeling and analysis of structural system. By using the analysis results maximum stressed beam to column connection is identified. The finite element model of a welded beam to column joint is modeled and the corresponding loading is applied. ANSYS software is used for the finite element modeling and analysis. The results are presented and conclusions drawn show that the equivalent structural stress method is a mesh-insensitive method and it has the capability of unifying different stress-life curves (S-N curves) into a single master S-N curve.

In the present investigation, the linear free vibration of carbon nanotube (CNT) reinforced cylindrical shell panel with a cutout is studied using the finite element method based on a higher-order shear deformation theory. A higher-order theory is used to properly account for transverse shear deformation. An eight noded degenerated isoparametric shell element with nine degrees of freedom at each node is considered. Results are presented for the variation of the fundamental natural frequency of functionally graded CNT reinforced cylindrical shell panel with cutout size. A few typical mode shapes are also presented.

Concrete Filled Steel Tubular section (CFST) is found to possess high strength and stiffness properties and has been popularized in high-rise building projects. Nowadays, several alterations are made within this section to improve its structural performance at design as well as at the constructional level. Concrete Sandwiched Double Steel Tube (CSDST) is one such configuration that provides improved fire resistance, impact resistance and efficient connection detailing, in addition to high strength, stiffness and ductility properties. Since experimental investigations become very expensive to study the various parameters influencing their behavioural aspects, numerical techniques are adopted in recent studies. Even though numerical simulations bring ease in performing parametric studies, a well-established theoretical background is needed to correctly interpret its output data. In this study, a numerical model is developed for two types of sandwiched tubes, namely, circular inner and circular outer steel tubes (CSDST CC), and square inner and circular outer steel tubes (CSDST-CS), using ABAQUS software. Here, the concrete confinement equation proposed by the author for CSDST cross-section based on thick-walled cylinder theory is used for defining the concrete material model. The numerical model developed is validated with the experimental results available for CSDS T stub columns. Further, a parametric study is conducted to find the limitations on the proposed concrete confining stress. The proposed equation is found to be valid for a wide range of hollowness ratio of the cross-section with compact (class-1) outer steel tubes.

The paper presents an experimental investigation using Aramid Fibre Reinforced Polymer (AFRP ) composites on the retrofitting of corroded Circular Hollow Steel Tubular (CHST) column under axial compression. So far, the experimental investigation was limited to the use of FRP such as Glass Fibre Reinforced Polymer (GFRP) and Carbon Fibre Reinforced Polymer (CFRP) and also the way of application of FRP on the structure, i.e., the wrapping system. A study for the expediency of AFRP fabrics in the axial strengthening of CHST columns was done in this paper. The disadvantage of AFRP is the cost alone, so the full wrapping of the CHST sections with AFRP will be pricey. The assets of AFRP over steel structures are the low weight, ease in application and with a limited approach it can cover a maximum area. Total ten samples were tested including control and wrapped specimen in various techniques until the failure mode. The results obtained from different experiments were compared with the control sample and later the load-deflection and stress-strain properties were studied. The results from the experimental investigation admitted that, the external wrapping of AFRP fabric strips undoubtedly build up the load carrying amplitude of the CHST columns. The increase in the number of the layers of AFRP strips also effectively deferred the local buckling of the CHST columns by increasing the vertical displacement.

Seismic design codes recommend Force-Based Design method for design of Steel Special Moment Resisting Frame (SMRF) buildings. FBD relies on capacity design principles to contain inelastic action primarily in beams in SMRFs during strong earthquake shaking. Therefore, in line with the strength hierarchy required in capacity design, seismic design codes recommend guidelines/procedures for the design of capacity-protected components (such as connections, panel zones, and columns) in SMRFs. Although, the intent of the recommended procedures is same across various seismic design codes in this regard, few critical differences persist between the procedures outlined in Indian seismic design code and other seismic design codes (more specifically, the American and the European ones). The key differences are: (a) in recognising the expected increase in material yield stress from the minimum specified, or characteristic, yield strength of the material, (b) in estimating the demand on and the capacity of panel zones, and (c) in recommending a minimum column to beam strength ratio (CBSR ) for the design of columns in SMRFs. To assess the implication of the identified critical differences, two buildings, a 3-storey and a 9-storey with steel SMRFs, are designed compliant to the Indian code; then, the performance of the two buildings is evaluated using nonlinear static and dynamic analyses. The performance assessment of the designed buildings indicates undesirable behaviour wherein conventional expectation of resisting strong earthquake ground motion through ductile flexural plastic hinge formation at the beam ends is not realised. Finally, the two buildings are redesigned to account for the three issues mentioned above. The redesigned buildings are seen to demonstrate acceptable earthquake behaviour. Hence, a need is perceived to update the seismic design provisions of the current Indian code for steel SMRFs to ensure acceptable behaviour of such buildings during earthquake shaking.

Seismic activities demand special design and detailing of Reinforced Concrete (RC) structures, possessing adequate lateral strength, ductility and energy absorption capacity. The shear strength, ductility and energy absorption capacity need to be established for the type of concrete and detailing of lateral reinforcement for ensuring safety of RC joint region. In order to achieve adequate shear strength and ductility, beam-column joints in MRFs need to be designed with High Strength Concrete (HSC) and good reinforcement detailing. The premature joint failure can be prevented when HSC is used in the joint region and hence ensures sufficient load carrying capacity and energy dissipation. This study attempts to accomplish and investigate the performance of five geometrically identical exterior RC beam-column joints with different forms of detailing of reinforcement and also with steel fiber reinforced concrete in the joint region under reverse cyclic loading. The beam-column joints designed for gravity loads and routine live loads made up of low strength concrete are vulnerable to diagonal shear cracking under seismic loading. Adequate anchorage length of beam bars with closely spaced horizontal hoop reinforcement and use of fiber reinforced high strength concrete in the joint region plays predominant role in enhancing the shear strength and performance. Adequate anchorage length of beam bars and good detailing of reinforcement improve the joint shear strength and reduce the joint stiffness degradation. The joint shear strength, ductility, energy absorption and hysteresis pinching response have been improved under reversed cyclic loading with steel fiber reinforced HSC in the joint region. The deflection of beam and the corresponding load at the ultimate stage increase with good detailing in the joint region. The addition of small quantity of steel fibers in HSC could alter the failure of joint from brittle to ductile under reversed cyclic loads.

Earlier in India, for the design of concrete bridges, IRC 18 and 21 were used which are based on working stress method. Later the codes were combined to IRC 112-2011 which is based on ultimate limit state method. IRC 112-2011 provides a very interesting design method based on a three-layer sandwich model for the design of flexural members. This method is based on three dimensional linear elastic finite element analysis. The three-layer sandwich model got evolved from the Wood Armer method which was recommended in the earlier version of Eurocode; EN1992-1-1:2001. This paper intends to compare the area of reinforcement obtained from the two design methods with the popular effective width method provided in IRC 112-2011 which is an empirical method. Slab culverts with varying spans subjected to different loading conditions provided in IRC 6-2016 are compared for the parametric study.

The research paper presents the experimental results of mechanical strengths as well as the durability of nano-fine cement incorporated concrete. The present study is dealing with the pulverising the ordinary Portland cement to the nanofine scale (~250nm) using the high energy milling process, which is a top-down approach. The fine grind cement is explicated by particle size distribution analysis and by analytical techniques. Pulverising able to produce 50% of the cement particles < 250nm after 90 minutes milling. In the present research 0%, 10%, 20%, 30%, 40% and 50% of nanofine cement as partial replacement of cement in concrete mixture with 0.45 water-cement ratios was used. Mechanical strength properties of concrete have been investigated, and durability study includes corrosion resistance as well as resistance to chemical attack. Based on the experimental data, concluded that the 30% nanofine cement as a partial replacement, improves mechanical strengths and corrosion resistance of concrete.

Transmission Line (TL) systems and the TL tower as support structures are the vital infrastructure facilities. Conventionally these towers are fabricated using Hot Rolled Steel (HRS) angle sections. Nowadays, the use of Cold-Formed Steel (CFS) is gaining popularity in construction of general steel structures due to its cost effectiveness and numerous other advantages. An attempt has been made in this research work to carry out the experimental investigations on X-bracing panel replicating substructure of a TL tower made of CFS lipped channel sections. Prior studies by the authors on probabilistic analysis of capacity/resistance of CFS columns suggested the distribution of resistance, with modelling error as random variable seems to follow lognormal distribution irrespective of the design standards, and COV for simulated resistance with modelling error, as random variable is 0.3. The results of experimental investigations on CFS panel indicated that the individual member capacities calculated as per ASCE 10-15 (2015) standard are higher as compared to the member forces corresponding to panel failure load. Hence, it is proposed to carry out the system reliability analysis considering the possible uncertainty parameters. Present studies brought out the importance of consideration of the modelling error associated with the member strength estimation models given in design standards along with the variations present in material properties and loading. Further, estimations of component reliabilities for the panel members may not provide actual failure probability for the system and hence it is necessary to carry out system reliability analysis. While evaluating the safety margins for various failure modes, in order to determine the overall reliability of structural system, it is important to consider the correlations arising from the common sources of loading and common material properties. In this study failure probability has been estimated considering the series system for critical members contributing to overall failure of panel.

This study focused on the enhancement of quality of coconut shell aggregate using different pre-treatment methods and their effects in lightweight concrete. The degradability of coconut shell aggregate was tested by exposing the aggregate to severe alkaline, acidic and sulphate solutions. The quality of this aggregate was improved by providing pre-treatment with different chemicals. The properties such as water absorption, aggregate impact value and aggregate crushing value were tested. It was observed that coconut shell aggregate treated with 20% Poly Vinyl Alcohol (PVA) improved the performance of the aggregate. For instance, the water absorption of PVA treated aggregate was reduced to 42.27%when compared to that of non-treated aggregate. Furthermore, the aggregate treated with 20% PVA showed a marginal (only 5%) improvement in the strength of coconut shell aggregate concrete. Therefore, it may be concluded that coconut shell aggregate may not degrade when it is bound with concrete.

In this study the long term compressive strength was evaluated for the concrete made with polypropylene fiber and copper slag. This study aimed to investigate the mechanical property of concrete and to develop regression equations to predict the long term compressive strength of concrete. Copper slag was replaced with fine aggregate by 0.0% (control mix), 20%, 40%, 60%, 80% and 100%. Fibrillated polypropylene fiber of 0.2% to 0.8% volume fraction was added as an admixture. Compressive strength of concrete was estimated at various curing ages of 7, 28, 56, 90 and 180 days. Copper slag 40% and PPF 0.4% gives an optimum value of compressive strength at 28 days. Compressive strength was predicted at these ages using SPSS tool. Compressive strength predicted by 28 days curing period shows good correlation with the experimental values at 56, 90 and 180 days.

Direct shear strength have been studied on conventional concrete and ternary blend fibre reinforced geopolymer concrete. Earlier studies indicate that when fibres are added to concrete, it enhances direct shear strength and contribute to a reduction in spacing and width of cracks. Studies on direct shear strength of Ternary blend Geopolymer Concrete (TGPC) has not been investicated. Also, the effects on the addition of fibres on TGPC is not yet studied. The paper is intended to provide a basic understanding of the direct shear behaviour of TGPC reinforced with steel fibers. This paper presents the results of the use of Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS) and Rice Husk Ash (RHA) as a ternary blend source material in Geopolymer Concrete (GPC). The study is limited to TGPC with 0.25%, 0.5%, 0.75% and 1% volume fraction of fibres. Push off specimen was used for studying the direct shear behaviour. It was found that fibre addition upto 1% delayed the crack propagation and showed better performance in the ultimate direct shear capacity and toughness than the conventional concrete specimens.

In recent times the Geopolymer Concrete (GPC) is gaining significance from the point of development of eco and environment friendly concrete using industrial by-products. The evaluation of mechanical characteristics of GPC paves the way for its structural use. In this paper the experimental study on shear strength of monolithic GPC interface is presented. This study includes different strength of GPC with and without reinforcement crossing the shear plane. The push off specimen prepared using GPC, were cast and tested. The results indicated that the shear strength of monolithic GPC interface has increased at higher rate up to GPC compression strength of 40 MPa. The presence of reinforcement across shear plane caused an increase of about 28% of the shear resistance against slip. The prediction equation proposed for the shear strength of GPC consists of contribution from friction, cohesion and dowel action of reinforcement at the interface. The push off test results was used to predict the coefficient of cohesion and coefficient of dowel action influencing the shear strength of GPC.

Concrete-Filled Steel Tube (CFST) columns combine the advantages of ductility, generally associated with steel structures, with the stiffness of a concrete structural system. Compared with the hollow steel tube columns, local buckling in the CFST columns is delayed due to the presence of concrete infill. Adding flutes to the columns can increase their moment of inertia and thus increasing the load resistance of the column. This paper presents the analytical and theoretical results of the study on behaviour of CFST columns with rectangular flutes. Normal grade concrete without reinforcement is used as in-fill. Number, position, and size of flutes are varied to understand the performance of flutes in structural strength enhancement of Concrete-Filled Rectangular Fluted Steel Tube Columns (CFRFST). Providing flutes is found to be beneficial and outward fluted columns are better than inward fluted columns. Four numbers of rectangular flutes provided outwardly of width D/3 and depth D/10 where D is the diameter of the CFRFST Column is found to be the most optimum cross-section of CFRFST columns considering the load carrying capacity and practical applications. Eurocode-4 is followed to generate non-dimensional P-M interaction curves for CFRFST columns with different steel contribution factors.

Shear strength is one of the important mechanical properties in the context of estimation of in-plane shear capacity of brick masonry piers or walls. This paper helps to identify the importance of standardization of test procedure and proposes a comprehensive test procedure for carrying out the shear strength test on brick masonry. Based on the identification that, dilatation is an important phenomenon in the shear strength test, a shear testing equipment that is capable for applying pre-compression using gravity is designed, fabricated and got employed in the experimental programme. The value of shear bond strength obtained from the test programme is quite comparable with the results available in the literature. However, for characterizing shear strength of brick masonry, results of the tests adopting a standardised procedure are required. It is also found that, in order to obtain COV of shear bond strength, it is important to carry out tests at more levels of pre-compression, not just three as is prescribed in many international standards.

The purpose of the present research is to investigate the shear behavior of fibre reinforced concrete beams under four point loading condition. Three types of fibres were examined: hooked-end steel fibre, crimped-steel fibre and continuous deformed-steel fibres. The experimental program consists of cubes to test the compressive strength of concrete, cylinders to test the tensile strength of concrete and beams to test the shear and flexure strength of concrete. Simply supported RC beams 150×150 mm cross section and 700 mm length were used in this study. The reinforcement was provided in three ways viz. conventional minimum steel reinforcement at top and bottom with stirrups in accordance with the provisions of IS 456, conventional minimum bottom steel reinforcement without stirrups incorporating crimped steel fibre in 03%, 0.4% and 0.5% dose and crimped steel fibre in 1.5% dose without top and bottom steel reinforcement and stirrups. The shear span to depth ratio was varied as 0.5, 1, 1.25 and 1.5. The experimental program consisted of twenty sets of beam specimens giving a total of forty beams in two replications each. The aim of this research is to investigate the effectiveness of fibres on the shear strength and ultimate load carrying capacities.

Presence of torsion makes the structural design of irregular buildings more complex and is prone to more severe damage. According to IS-1893:2016, a building is said to be torsionally irregular when the ratio of maximum horizontal displacement at any floor in the direction of lateral force to the minimum horizontal displacement at far end is more than 1.5. The torsional forces acting on a building are influenced by the relative location of the centre of mass, the centre of strength and the centre of stiffness. Therefore, these centres of significance shall be located aptly to minimise torsional effects on buildings to ensure efficient building structure. In this paper, the effects of strength eccentricity and stiffness eccentricity with respect to the centre of mass of the building are evaluated and non-linear dynamic analysis is carried-out to study the variation on torsional irregularity ratio and other torsional parameters. For the building structure, the structural configuration together with the sizes of structural elements are varied repeatedly to find-out the best locations of mass, stiffness and strength centres to minimize the torsional irregularity ratio. The study is found to be very productive as the torsional irregularity ratio gets reduced very significantly.

The main problem in the landing gear dynamics of the aircraft is either shimmy or brake induced vibration or ground induced longitudinal and lateral excitation due to runway unevenness. Neither of these vibrations is catastrophic, but still causes huge discomfort to pilots and passengers. Investigations on brake vibration were required, where a study of landing gear vibration due to brake chatter and squeal during taxi and landing was performed. It is essential to analyze vibration in aircraft due to the fact that while take-off and landing a very massive force acts on the landing gear, which tends to produce kinetic energy. Vibration would leads to the gradual deterioration of aircraft structure, which in turn affects both the passengers and crew. All vibrations have associated frequencies and magnitudes that should be identified. Basic dynamic theoretical studies of landing gear by modal and frequency response analysis using finite element method points out the design considerations required to reduce the level of vibration. An attempt has been made to reduce the vibration by providing stiffeners at the sensitive locations obtained using strain energy values and results were presented and compared for nose landing gear with and without stiffeners.

The technology of Geopolymer Concrete (GPC) is gaining importance in the present era because of the reduced carbon dioxide emission and low embodied energy, when compared with the conventional cement concrete. GPC is obtained by the activation of silica and alumina rich source materials in the presence of alkali activator. This paper evaluates the strength and durability characteristics of fly ash based GPC with ferrochrome slag aggregates. The fine and coarse aggregates in the GPC were replaced with ferrochrome slag in various proportions, and it was noted that the coarse aggregate replacement performed better than the replacement of fine aggregates. The optimum replacement percentage that gives the maximum strength in terms of coarse aggregate replacement was arrived at. The result concluded that the incorporation of ferrochrome slag as coarse aggregate at optimum level enhanced the strength characteristics in comparison with the conventional GPC with normal aggregates. The durability characteristics of the various replacement mix was carried out, and the results of the optimum replacement mix was compared with the conventional geopolymer mix. Apart from these, the feasibility of utilising ferrochrome slag as aggregates in concrete were also ascertained by leaching tests.

Axial force-moment interaction of Steel-Concrete Composite Shear Wall (SCCMSW ) under seismic loading is the focus of present study. Conventional Reinforced Concrete Shear Wall (RCSW ) is made composite by embedding vertical steel sections in the end zone. Current literature shows that, such composite sections are not addressed in developing countries codes. A new extended method to develop axial force-moment (P-M) interaction for SCCMSW , based on Eurocode 4 (2004) has been proposed and the results were compared with that obtained from SAP2000 v14 program for validation. Nonlinear static analysis has been performed to study damage pattern. It is concluded that the performance of frame with SCCMSW system is more efficient in terms of lateral stiffness and ductility than RCSW..

This paper reports the workability and compressive strength behaviour of geopolymer concrete using fly ash as the source material for the first part of the study. Also, partial replacement of fly ash by Ground Granulated Blast Furnace Slag (GGBFS) with 10%, 20%, 30% and 40% were investigated with varying NaOH concentrations of 8M, 10M, 12M and 14M. The workability of geopolymer concrete and its hardened properties were studied using different tests for flowability as per EFNARC specifications and Indian standard specifications, respectively. For the second part, the 28 days matured specimens were subjected to elevated temperatures from 200°C to 1000°C with an interval of every 200°C and their corresponding weight loss and deferred strength were studied. The test results indicated that the compressive strength of specimens under normal air curing increases with addition of GGBFS as partial replacement of fly ash up to 30% beyond which the strength decreases marginally. Also, the compressive strength values increase with increase in NaOH concentration up to 12M. Further, the increase in NaOH concentration to 14M shows a decrease in the compressive strength of Self-Compacting Geopolymer Concrete (SCGC) irrespective of the addition of GGBFS dosage. Tests on SCGC subjected to elevated temperatures showed that for all cases, the compressive strength value decreases gradually with an increase in temperature up to 400°C beyond which a steep decrease in compressive strength was found until 1000°C. The effect of elevated temperature on the compressive strength of SCGC had a direct relation with that of the weight loss with increase in temperature. The SCGC specimens prepared with 12M NaOH concentration and with 30% GGBFS as partial replacement of fly ash yielded the maximum strength with the different combinations experimented.