The Studies On Seismic Reliability Of Isolated Structure Based On Probability Statistics Method

Seismic isolation is a technique to reduce earthquake excitation by placing horizontally flexible isolation devices at the base of the structure to physically decouple it from the ground. For earthquake excitation reduced,floor acceleration and inter-story drift demands on the superstructure(structure above the isolation system) are reduced by comparison to the equivalent non-isolated structure, thus isolated structures should have better seismic performance, but in the Code for Seismic Design of Building, isolated structures seismic performance is still satisfied to the targets, i.e, undamaged under frequent ground earthquake, repairable under basis ground earthquake, uncollapsed under rare ground earthquake. Moreover, the above targets are expressed as the certainty index. Considering randomness of earthquake and structure parameters, this paper investigates dynamic reliability of isolated structure under the various earthquake levels. The main content is following:1. The performance function of isolated structure under different level of ground motion are defined. The approximate seismic reliability method of isolated structure is obtained.2. The finite element model of two isolation buildings are obtained and the response of buildings are calculated by inelastic time history analysis. Based on the results, the response probability parameters value and probability distribution law of isolated buildings are analyzed by probability statistics method.3. Combining numerical simulation with experimental data of properties of rubber bearings, we can obtain the probability distribution law and probability statistics parameter of ultimate properties of Chinese rubber bearings.4. Considering the failure of isolation bearings and superstructure, the failure modes of isolated building are given. The dynamic reliability of two isolated building are calculated by the approximate seismic reliability method and the seismic performance of the two isolated buildings under different level of ground motion are investigated.The main conclusions are obtained:(1)The responses of isolated structures, including the maximum floor drift ratio of superstructure, the maximum floor acceleration of superstructure, shear strain of rubber bearing, and compressive stress of rubber bearing, all follow logarithmic normal distribution.(2)The ultimate shear strain and ultimate compressive stress of rubber bearing all follow lognormal normal distribution. The mean of ultimate shear strain is 390% and the mean ultimate compressive stress is 28 MPa.(3) If isolated structures meet the Code for Seismic Design of Building, they can reach the demands, i.e, undamaged under frequent ground earthquake, repairable under basis ground earthquake, uncollapsed under rare ground earthquake. Moreover, they can reach the high demands, i.e, undamaged under basis ground earthquake, repairable under rare ground earthquake, uncollapsed under very rare ground earthquake.