Effects of Fundamental Natural Time Periods on the Seismic Performance of Base Isolated Multistory Buildings

Abstract

This research is mainly dealt with determining the effectiveness of base isolation in multiple degree of freedom systems (MDOF) of different fundamental natural time periods (FNTP). Base isolation devices avert the detrimental ground shaking to maximum extends and mitigates the lateral forces caused by earthquakes. In this research, it is intended to study about under what circumstances base isolation system will be effective in reducing the lateral forces caused by earthquakes. Every MDOF system will be having its own FNTP with respect to its mass, stiffness and damping matrices. In order to determine the effectiveness of base isolation, five number of five-story buildings of different FNTP, i.e., 0.4 sec, 0.8 sec, 1.2 sec, 1.6 sec and 2.0 sec had been selected. Different FNTP were obtained by maintaining constant mass as well as damping matrices while changing stiffness matrix for each building. Subsequently, comparison was made between the structural responses of buildings with and without providing base isolation. Finally, it was found out that a building of lower FNTP was performing well when it was provided with base isolation.