PASSIVE CONTROL-SYSTEMS FOR SEISMIC DAMAGE MITIGATION

This paper proposes a simplified theory to predict and compare the sei smic performance of viscoelastical (VE)- and elastoplastical (EP)- dam ped passive control systems, and to demonstrate their ability to prote ct structures during a major seismic event. Closed-form expressions fo r ''equivalent period'' and ''equivalent damping'' of these systems ar e proposed by idealizing them as linear single-degree-of-freedom (SDOF ) systems. The expressions are used to clarify and compare the structu ral parameters, seismic drift, and force for the systems, based on a c ommon high-damping linear spectrum. By extending the SDOF theory, a se ismically deficient 14-story steel moment resisting frame (MRF) is upg raded by inserting VE or EP dampers. Extensive three-dimensional multi -degree-of-freedom nonlinear dynamic analyses are performed for the MR F, VE system, and EP system using earthquakes of various intensities. The 14-story VE and EP systems responded as predicted by the SDOF theo ry. They show much smaller drifts than the original MRF, keep frame me mbers elastic, and protect nonstructural components, even against majo r earthquakes.