STUDY ON FORTIFICATION CRITERION AND QUANTIFIED PERFORMANCE INDEX FOR REINFORCED CONCRETE BRIDGE STRUCTURES IN PERFORMANCE-BASED SEISMIC DESIGN

Because the consideration is quite simple in an earthquake hazard level and a marked difference in probability of exceedance between earthquake action E1 and earthquake action E2 in guidelines for seismic design of highway bridges, a new definition of earthquake action E1′ with the occurrence probability of 40% in 50 years and earthquake action E2′ with the occurrence probability of 2%-3% in 50 years is proposed, and the bridge structure performance levels categorized into five grades are established. Seventeen structure performance objectives and four seismic fortification criteria are formed. To relate bridge component to its mechanical properties at the five designated performance levels, component performance levels for different seismic fortification criterion in C bridge structures are established. It is expected that performance-based seismic design for bridge structure can be improved. Based on the statistical data of 127 seismic performance tests of RC bridge columns with circular section subjected to flexural failure, five indices for the same five designated performance levels are put forward. Comparing the drift ratio of five designated performance levels with the provisions among New Zealand standard, Japan design code, and American design code, the results show that the drift ratios for five designated performance levels is reasonable and effective. It can be used to determine displacement of pier top in the performance based seismic design. In view of performance objectives dependent on a large amount of experimental results, evaluation template for experimental results is proposed.