Stochastic analysis of seismic base isolated structures

ABSTRACTIn the last decades, many sever earthquakes shaked-up the world.~ These earthquakes orientJengineers to search for safe and economicapproach to protect structures from the hazardous effects of the nextearthquake.The ”Base Isolation System” provides a new method to control theseismic response of building structure and it is very effective, safe,simple and can be used in very wide range. It can keep the structureworking in elastic range in earthquake, so it can be used in differentkinds of important buildings in different seismic zones. It can be used innew buildings, also can be used in existing buildings to improve itsearthquake resistant ability.Due to the large uncertainty III peak acceleration, vibrationcharacteristics, and the time duration of the ground acceleration, theinput dynamic excitations and the structural responses are treated asrandom time functions.The stochastic analysis of base isolated structures is studied alongwith all important subjects needed for the study. The theories of randomvibration are represented and applied on linear analysis of structures.Also, The statistical linearization technique is used to investigate thestochastic non-linear behaviour of structures, under excitation of filteredand white noise processes.The results of stochastic analysis of base isolated structures arecompared with the fixed base structures. A parametric study is carriedout to investigate the efficiency of base isolation technique. Theparameters are base frequency ratio, base mass ratio, post-pre yieldstiffness ratio of isolator device, isolator yield displacement,superstructure damping ratio, and isolator damping ratio.