Reliability of semi-active seismic isolation under near-fault earthquakes

Abstract

Abstract Structural control can be used for protecting buildings and its vibration-sensitive contents from earthquakes. Seismic isolation is a passive control system that lowers effective earthquake forces by utilizing flexible bearings. However, supplemental damping in the isolation system may become necessary to reduce large isolator displacements under near-fault earthquakes. Semi-active dampers are preferred over passive dampers because of their capacity in minimizing possible amplifications in floor accelerations due to increased damping. Semi-active dampers are also preferred over the active ones because of their higher stability and lower power consumption. On the other hand, seismic performance of semi-active isolation may vary due to variations in the mechanical properties of semi-active devices and/or seismic isolators. Such uncertainties alongside the uncertainties associated with ground motion parameters should be taken into consideration to develop a realistic picture of the behavior of seismically isolated buildings equipped with semi-active control devices. The objective of this study is to examine the effectiveness of semi-active isolation in protecting vibration-sensitive equipment and integrity of a structure by considering the aforementioned uncertainties and present the reliability of semi-active seismic isolation under near-fault earthquakes. For this purpose, this paper introduces a method that uses synthetically generated near-fault earthquakes and Monte-Carlo Simulations. This method is used to determine the reliability of a 3-story and a 9-story benchmark buildings with semi-active isolation systems under near-fault earthquakes of various magnitudes and varying fault distances. The results are presented in the forms of comparative plots of probability of failure and reliability.