The use of innovative base isolation systems to achieve complex seismic performance objectives

Description

To investigate possible improvements to the design of isolated structures, an extensive research program was conducted. Analytical and experimental investigations are presented to characterize multi-stage spherical sliding isolation bearings capable of progressively exhibiting different hysteretic properties at different stages of response. This newly developed triple pendulum isolator incorporates four concave surfaces and three independent pendulum mechanisms. This thesis summarizes shaking table test results on a 1/4-scale seismic isolated steel braced frame on multi-stage bearings. Harmonic characterizations tests and earthquake simulations were conducted considering various levels of response, multi-component excitation, bearing uplift, and superstructure response. These experimental results are used to validate an analytical model which is then implemented as part of a parametric study of single- and multi-story buildings incorporating a wide class of isolation systems. Behavior of the new triple pendulum bearing is compared with that of linear isolation systems with both nonlinear viscous and bilinear hysteretic energy dissipation mechanisms. From both incremental dynamic analysis and an ensemble of response history analyses, important response parameters for the isolation system and superstructure are reported for all cased considered. Results of parametric analyses are used to develop a multi-level, performance, design framework. The new triple pendulum bearing, along with certain classes of viscous and hysteretic devices, are found to exhibit favorable characteristics toward achieving complex seismic performance objectives.