Analyses of Seismic Structures and effect of Higher Modes on Residual Mode Method

Abstract

In earthquake resistant design of building structures, priority is given to protection of human lives against infrequent but large earthquakes. Following the experiences of building performance from a large number of recent earthquakes all over the world, a lot of research is being carried out in this field. Based on the concept of saving human lives, in conventional seismic design, acceptable performance of a structure during earthquake ground shaking is linked to the lateral force resisting system being able to absorb and dissipate vibrational energy due to ground motions in a stable manner for a large number of cycles of motions. Energy dissipation generally occurs in specially detailed ductile plastic hinge regions of beams and column bases, which also form part of the gravity load carrying system. The proposed methodologies used and recommendations specified by seismic structure codes of training for the seismic analyses of structures, when high frequency modal responses are involved are reviewed. The effect of the damping ratio on the rigid response coefficient is studied for different earthquake ground motions.