Vertical progressive collapse mechanism and influencing factors of base-isolated structures
DU Yong-feng1,2, DUAN Hao-cai2, XU Tian-ni2
1. MOE Western Engineering Research Center of Disaster Mitigation in Civil Engineering, Lanzhou University of Technology, Lanzhou 730050 China;
2. Institute of Earthquake Protection and Disaster Mitigation, Lanzhou University of Technology, Lanzhou 730050, China
Abstract：The vertical progressive collapse mechanism of base-isolated structures and influences of structural parameters on the collapse mechanism were studied. Firstly, vertical pushdown tests of a single plane RC base-isolated frame were used to verify its simulation model built with the finite element software SeismoStruct. Then, SeismoStruct software and the nonlinear pushdown analysis method were adopted to analyze and compare multi-group FE structure models with different slab types, isolation bearings and aseismic designs. The results showed that slabs enhance the progressive collapse resistance capacity of base-isolated frames with beam action mechanism; the anti-progressive collapse capacity enhancement of frames with catenary action mechanism depends on the action width of slabs; With increase in fortification intensity, the anti-progressive collapse capacity of frames under both beam action mechanism and catenary one increases, but the capability increase in frames under beam action mechanism is more obvious; compared with non-base-isolated structures, the failure of base-isolated frames under beam action mechanism can be delayed in some cases due to constraints reduction of isolation layer; while the effects of increase in isolation layer horizontal stiffness on the vertical relative load-bearing capacity of base-isolated structures are small.
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