Dr. Irshad Qureshi, Assistant Professor, Department of Civil Engineering, University of Engineering and Technology, Pakistan

Biography: Dr. Irshad Qureshi is Assistant Professor at Civil Engineering Department of University of Engineering and Technology, Taxila. He obtained his Master and Doctor of Engineering Degree from the Asian Institute of Technology, Thailand. His doctoral research work was focused on the seismic behavior of rocking wall structures which included an in-depth modeling of static and dynamic behavior of rocking wall structures and the development of design methods to predict their seismic demands. He has also worked on several projects regarding the performance-based seismic evaluation of existing infrastructure in developing countries. Currently, he is involved in projects ranging from seismic risk mitigation to development of numerical models for innovative structural systems. His areas of interests are earthquake engineering, seismic risk mitigation and management, performance-based seismic design/evaluation and seismic performance of innovative structural systems.

Speech Title: Numerical Modeling of Rocking Wall Structures including the Impact-Induced Effects

Abstract: Recent earthquakes in various parts of the world have shown that life-safety performance of structures alone is not enough as the structures exhibited intense damage requiring a costly retrofitting or in some cases demolishing and rebuilding of structures. Therefore, focus is increasing on the use of resilient lateral force resisting system capable of not only surviving the earthquakes but also keeping the damage to a minimum level. Precast post-tensioned rocking wall system is such a solution and for it to be presented as a viable alternative to conventional shear wall structural system, reliable numerical models, capable of predicting their behavior both in static and dynamic domains, are required. Along with the modeling of geometric and material nonlinearity, the contact and impact behavior at the rocking joints poses unique challenges as for as numerical modeling is concerned. This talk is focused on the development and validation of fiber and finite element models using the results of a shake-table test. Experimental results showed the high-velocity contact at the wall-foundation joint to induce high-frequency acceleration spikes in both horizontal and vertical directions. Acting together, these acceleration spikes can cause shear slip and can jeopardize the overall stability of the system and therefore needs to be modeled accurately. The proposed numerical models have been found to be reasonably accurate in predicting the overall behavior of rocking walls including the acceleration spikes. Further investigation into these acceleration spikes based on the validated numerical models have shown that the acceleration spikes are dependent on the lateral velocity at impact and the initial contact stiffness. So, a velocity-dependent energy dissipation device along with a soft contact can reduce these effects significantly.