DAMAGE FRAGILITY ANALYSIS FOR HIGH-PIER AND LONG-SPAN CONTINUOUS RIGID FRAME BRIDGE UNDER SCENARIO EARTHQUAKES

摘要

The primary target of performance-based earthquake engineering(PBEE) is to predict the seismic performance of structure with a certain level of exceeding probability, since there are uncertainties inherent for seismic demand and structural capacity. In this study, a pivot rigid frame bridge with high pier and long-span continuous girder is investigated based on fragility curve theory with incremental dynamic analysis (IDA) under 20 earthquake records selected, which is designed to the seismic code of railway engineering. And analytical damage fragility function is developed based on strain limit states defined in the stress-strain relation of confined concrete and steel from experimental damage data of bridge piers. The upper bound and lower bound of seismic performance of whole bridge are predicted from the fragility curves of the critical components. The result indicates that lower and moderate level of earthquakes result in damages with exceeding probability of 0.00128 and 0.11375 as upper bound of damage state, and high level of earthquakes can be controlled within the upper bound damage fragility of 0.74443 with extreme low probability for collapse, which qualifies the three level performance of seismic design in term of damage fragility.