Recently Completed Projects
Development of Mitigation Strategies for Structures Located in Seismically Prone Regions
- Towards developing innovative experimental and analytical methodologies for mitigating seismic distress of seismically vulnerable structures, dynamic characterization studies were carried out on supplemental damping devices like Shape Memory Alloy(SMA) wire damper, Lead Extrusion damper, X-plate Metallic Elasto-plastic damper, Rubber based Visco-elastic damper for passive control and Magneto-rheological (MR) damper for semi-active control.
- A methodology to assess the level of severity of Open Ground Storey (OGS) building was developed Displacement Demand Capacity Ratio (DCR) was used to evaluate the severity of risk of an OGS building for local seismic hazard. The proposed methodology was validated with the pushover analysis made on typical multi-storied building model using SAP software and shake-table experiments conducted on a three storey model OGS building. The proposed methodology was found to give fairly good matching in case of plan symmetrical buildings.
- The seismic distress mitigation methodology developed for seismically vulnerable OGS structures was successfully implemented in a seismically damaged three storey RC frame building retrofitted using X-plate ADAS elements. The building was locally repaired in the ground floor columns using Geo-polymer concrete composite and seismically retrofitted using X-plate based ADAS elements in the bottom storey. Reaction mass shaker test followed by shake table tests were performed on this retrofitted OGS structure and the improved seismic due to retrofit were evaluated.
Shake table testing of OGS building retrofitted with X plate metallic supplemental devices
Shake Table Studies on RC and Brick Masonry Buildings
In the past, during earthquakes, numerous RC buildings had been damaged due to structural irregularity, including torsional and vertical irregularities. Irregularity in structural configuration of a building thus plays an adverse role in its seismic behaviour and has to be studied experimentally and analytically. With the state of art facility available, CSIR-SERC has
- Investigated on comparative Seismic Performance of Model RC Frames with/without Vertical Irregularity,
- Involved in development of suitable retrofitting schemes for the various structural elements and systems,
- Evaluated the performance of soft storey buildings and retrofitted brick masonry structure under seismic loading.
Development of Passive Energy Dissipaters / Semi Active Dampers for Seismic Protection of Structures
Development of Passive Energy Dissipaters / Semi Active Dampers for Seismic Protection of Structures
- A novel design philosophy of seismic resistant design using dampers is being actively pursued. The seismic dampers have many variants, depending on the philosophy of energy dissipation.
- CSIR-SERC has designed, developed and patented many of these devices after subjecting them to a rigorous experimentation regime.
The type of dampers include
- metallic-yielding based X-plate
- triangular devices and lead extrusion dampers
- visco-elastic solid high damped rubber based devices
- semi-active magneto rheological fluid based devices and re-centering
- shape memory alloy based devices
The design methodology developed is validated with shake table testing on model structures with dampers
Seismic Base Isolation Device
- CSIR-SERC in collaboration with M/s Rubber board of India has developed cost-effective and indigenously designed and developed natural rubber based seismic isolators, as an effective device for seismic mitigation.
- Software for carrying out the design of seismic base isolators has also been developed.
- An elaborate testing programme, including shake table testing is being conducted towards bench-marking the robustness of the material and its design philosophy.
- Suitable and ready-to-use design charts are also developed for use by design engineers.
Stability and Seismic Fluid-Structure Interaction Studies on Spent-Fuel Storage System
- Seismic safety of liquid-filled containers is of great concern in view of the potential economic loss that might be incurred due to structural failure of the liquid container as well as the potential environmental impact, the spilling of the contained liquid might have to the surrounding area.
- Various codes specify lesser values of response reduction factors and higher importance factor as they have higher utility and damage consequences. But there exists significant qualitative and quantitative differences among various codes of practice.
- Experiments using simulated loading facilities help to understand the behaviour of structures during seismic loading.
- Towards this, a tank has been designed to suit the experimental requirements. The seismic tests were carried out on the shaking table and the quantities of interest such as hydro dynamic pressure on the wall, accelerations inside the liquid and outside tank wall, sloshing height of the liquid have been examined. These experimental results were used to refine the analytical prediction of structural and hydro-dynamic response parameters. Sophisticated instrumentation like underwater accelerometers, high speed camera based displacement measurement devices were used for this test.
- Number of stacks of spent fuel assembly that can be safely assembled in the water-filled tanks at each nuclear power plant is estimated by fluid structure interaction experiments of tanks with spent fuel storage stacks, enabling our nuclear plant system for a transparent verification by IAEA
Impact Load Testing of First Indian All-Composite Revathi Antenna
CSIR-SERC carried out Qualification tests on the design of the ship-mounted, all-composite, first Indian antenna through a specifically designed 25-g shock testing machine.
The experimental verification on these composite antennas in the three orthogonal directions viz. vertical, horizontal and longitudinal is the first time in the world using the newly developed experimental facility.
- The shock loading adopted in the vertical direction consisted of applying a specific number of half sine shock pulses of 25g magnitude and 6 milli-second duration.
- Similarly, the shock loading adopted in the horizontal and longitudinal directions consisted of applying a specific number of half-sine shock pulse of 12g magnitude and 6 milli-second duration.
- Instrumentation consisted of accelerometers and strain gauges and the displacements were captured using a high speed motion camera and processed by image processing software.
Multi-Support Excitation Experiments of Control and Safety Rod Drive Mechanism
The safety of the nuclear reactor and the fail-safe shutdown systems under seismic events is ascertained by these scram ability experiments and drop-time measurements of the CSRDM, DSRDM and PSS safety rods under site-specific seismic inputs.
- Done for the first time in south Asia, which has been pending in the Indian nuclear scenario for four decades.
- Seismic qualification of Control and Safety Rod Drive Mechanism (CSRDM) of a Prototype Fast Breeder Reactor (PFBR) was successfully conducted for the first time in India using the pseudo-dynamic test facility established at CSIR-SERC.
The safe functionality of the dropping mechanism was successfully ensured during multi-support seismic excitation under OBE (operational Basis Earthquake) and SSE (Safe Shutdown Earthquake) conditions.
Studies on Non-Linear Behaviour of Shear Walls
- Shear walls are the ideal choice to resist lateral loads in multi-storied Reinforced Concrete (RC) buildings. Shear walls provide large strength and stiffness to buildings in the direction of their orientation (in-plan), which significantly reduces lateral sway of the building.
- The promise of Performance Based Seismic Engineering (PBSE) is to design and construct structures, with predictable seismic performance. To translate this promise into reality, design of structures impose the criteria for ductile failure in addition to strength and stability criteria.
- Towards this, CSIR-SERC has carried out detailed Pushover monotonic load tests, Cyclic load tests and shake table tests on Shear Walls.
Improved Design and Retrofit Methodology for Seismically Vulnerable Open Ground Storey Structures
Open Ground Storey (OGS) structures bore the brunt of seismic damage in the Bhuj (2001) earthquake. Functionally, these are built for the purpose of parking of vehicles by removing the in-filled walls in the ground storey. This causes a discontinuity in the lateral stiffness and lateral strength along the vertical direction thus imposing large displacement demand on this open ground storey. Hence, a need exists for developing improved design and retrofit methodologies for these special class of buildings in India. Conflict demand between seismic safety and functional requirement, and moreover the huge number of OGS buildings in urban areas in India necessitates the seismic vulnerability assessment of existing OGS buildings. The project proposes a methodology for seismic vulnerability assessment of existing OGS buildings and design guidelines for new buildings. Feasibility of various retrofit strategies for OGS buildings will be explored.
Magneto-Rheological Elastomer based Smart Seismic and Vibration Isolators
- The project aims to develop Magneto-rheological elastomer (MRE) based base isolation systems as an adaptable smart base isolation system.
- The developed base isolation is adaptable, hence the large seismic gap demanded by the conventional seismic isolation can be controlled
- These isolators can be conveniently used in various ground excitations (near faults and far fault earthquakes), thus eliminating the need to design based on environmental conditions
- MREs are capable of adjusting their modulus or stiffness depending on the magnitude of the applied magnetic field. The isolated foundations supporting sensitive equipment that needs protection from incoming vibration and shock can be immensely benefited from the smartness of the MREs.
- Existing isolators for reducing the transmissibility of forces from machinery have been passive and are not adaptable. Conventional vibration isolators requires change in elastic properties and stiffness to cater to the changes in excitation frequencies. Use of MRE isolators shall ensure a constant isolation efficiency for a wide range of machine frequency excitations.