Study On Probabilistic Seismic Demand And Capacity Analysis For Regular Bridges

Regular bridge, as one of the most widely used types of bridges in highway engineering, meanwhile one of the most vulnerable types of bridges under the action of earthquakes, whose seismic design has been the focus of earthquake researchers. In this paper, the key issues about seismic demand and capacity in performance-based seismic design for regular bridge have been studied. The main research works and conclusions are as follows:(1) Based on the previous researches, the damage states of pier are proposed as the basis of the performance levels of regular bridge. This paper describes five limit states of pier with the corresponding control conditions. According to the five limit states proposed by this paper, the performance levels of regular bridge are divided into six states criteria.(2) Displacement drift ratio was selected as the design parameter of regular bridge. The probability distribution of target displacement drift ratio is researched based on the statistical analysis results of cyclic test for flexure dominated reinforced concrete piers. This paper identifies the one-side lower confidence limits of the target displacement drift ratio with 95% confidence on the basis of mathematical analysis software. At last, the practical performance quantitative index for regular bridges is determined.(3) A large number of earthquake records are selected to perform a series of time history analyses for the simplified models of regular bridge based on the software of OpenSees in order to consider the uncertainty of ground motion. Using the results of comprehensive dynamic analyses, series "clouds" of IM-EDP (intensity measures-engineering demand parameters) pairs of different soil sites and different fundamental period are generated. It is suggested that the spectra acceleration and drift ratio present definite linear relation in natural logarithmic coordinates.(4) Through the regression analysis of the "clouds" of spectra acceleration-drift ratio pairs in natural logarithmic coordinates, simplified calculation formula of probabilistic seismic demand of regular bridge is derived. It shows that the simplified calculation formula has a satisfactory accuracy on estimating the seismic response of regular bridge from the case study of an actual project.