Effects of the Mechanical Characteristics of LRB's on Structural Response of Base Isolated Buildings

Abstract eng:
This study examines parametrically the response of a seismic isolated multistory-structure. The characteristics of the isolation system are based on the analytical investigation and results from a dynamic thermo mechanical analysis (TMC) of a characteristic Lead Rubber Bearing (LRB). The parametric analyses of the structure are based on seismic records and provisions for seismic isolation. For the aforementioned structure, nonlinear dynamic history analyses are performed using three accelerograms in order to have a more accurate picture of the contribution of the base isolation system to the total seismic forces that are developed at the superstructure during seismic excitations. It must be noted that the response of the superstructure is considered to be elastic, while the response of the seismic isolation bearings is inelastic. For the time-history analysis the model is subjected to three scaled seismic excitations, given by the horizontal accelerograms of El Centro, Kalamata and Thessaloniki earthquakes. Furthermore, an iterative process has been adopted to design the bearings according to code provisions and researches on seismic isolation of structures. The aim of these parametric analyses is to investigate the influence of the LRB mechanical characteristics in the superstructure response. More specifically, the superstructure response is examined for the expected variations of the lead’s yield stress values. These variations are related to the temperature that is developed in the lead core of the LRB, due to the convertion of plastic work into heat by the seismic excitations.

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