The Movement Characteristics Of Near-fault Ground Motion And Influence On Fragility Analysis Of Base-isolated Structure

With the study of base isolation technology and the experience accumulated, base-isolated structure is more and more widely used at home and abroad. But due to the limited number of base-isolated structure and the fewer times are subjected to real earthquake or other reasons, resulting in earthquake engineering lacks a certain amount of base-isolated structural earthquake damage data, particularly of base-isolated structure subjected to near-fault ground motions of the performance. To better understand the seismic performance of base-isolated structure, it is necessary to analyse the fragility of structures. Therefore, the performance issues of structure were analyzed by the near-fault ground motion. The near-fault ground motion characteristics, the structural performance level, the performance indicators corresponding to each limit states, and the fragility were also researched. Details are as follows:(1) The research results and trends on isolated structure at present were summarized and analyzed. The seismic performance of isolated structure has aroused wide attention after the damage of strong earthquakes in recent years. So it is significant to research the fragility of isolated structure based on near-fault earthquake of movement characteristics.(2) Based on near-fault earthquake of movement characteristics(velocity pulse effect, fling-step effect, hanging wall effect, and directivity effect), choosing Taiwan Chi-Chi to near-fault ground motions by the analysis required, and examining the effects on dynamic frequency spectrum characteristics by the characteristics of near-fault ground motions.(3) Introducing the earthquake reaction analysis method on base-isolated structure. Based on near-fault earthquake of movement characteristics, choosing split forward directional pulse type, and sliding rushed effect pulse type, and no pulse type amounted to 30 ground motion records. Choosing PGA as the ground motion intensity index, the incremental dynamic analysis(IDA) method is used to calculate the structure, and the peak inter-story drift ratio of super structure and the isolation bearing deformation are selected as structural performance index, a classification of performance level and the limits of quantitative index for base-isolated reinforced concrete frame structure are suggested on the basis of previous studies.(4) Considering the hanging wall effect of near-fault earthquake of movement characteristics, selected 20 near-fault ground motion records from the ATC-63, choosing PGA as the ground motion intensity index, by dynamic nonlinear analysis, structural fragility curves obtained. And the analysis results showed that the obvious hanging-wall effect.(5) Considering the directivity effect of near-fault earthquake of movement characteristics, selected 20 near-fault ground motion records from the ATC-63, choosing PGA as the ground motion intensity index, by dynamic nonlinear analysis, structural fragility curves obtained. And the analysis results showed that the obvious directivity effect.Results above can provide a reference for engineering design, and the fragility curve be obtained provides the basis for the development of disaster prevention and post-disaster assessment.