A Study On Seismic Fragility Analysis Of Continuous Rigid-Frame Bridge Based On Chinese And American Seismic Design Standards

Earthquake is a common natural disaster with high randomness and strong destructive power. Bridge, a lifeline engineering, plays an essential role in the process of earthquake relief work. In the field of anti-seismic control of highway bridges, different standards for antiseismic design are formulated according to various natural conditions and operating requirements of each country. With the rapid development of road and bridge transportation network, continuous rigid frame bridges have become one of the main bridge types which can cross deep grooves and dangerous ravines for the advantages of great crossover capability, good ride performance and adaptation, as well as reasonable force. Continuous rigid frame bridges are progressing toward high pier and large span. However, its seismic design is comparatively lagging behind its practical application. Seismic fragility curves, as one of the most efficient approaches to express the correlation between structural damage probability and ground motion intensity, have important significance for the appraisal of economic losses and structural performance, as well as the project maintenance after the earthquake. Therefore, the study on continuous rigid frame bridges based on different standards for anti-seismic design and seismic fragility has great significance for ensuring the anti-seismic safety of such bridges.This article is aiming to perform seismic design of 98m+180m+98m large-span prestressed concrete continuous rigid frame bridge with double thin-wall piers, based on Chinese current Guidelines for Seismic Design of Highway bridges(JTG/T B02-01-2008) and American AASHTO Guide Specifications for LRFD Seismic Bridge Design 2011.The author analyzes the bridge seismic fragility of engineering project by modeling and nonlinear timehistory analysis. It hopes to provide reference for the seismic design of continuous rigid frame bridge in China by comparing and analyzing the results. This article performs the following sections:(1) After a review of a large number of domestic and foreign materials and literature, the author summarizes the seismic design concepts frequently-used in bridge seismic design and research achievements related to bridge seismic fragility; introduces the principles of seismic fragility analysis; summarizes the construction method of seismic fragility curves;(2) The author summarizes the theoretical similarities and differences of Chinese and American seismic design standards; performs design calculation of Canglangzhou Hanjiang Bridge in Yunxian County by dynamic and time-historical analysis under two standards and then carries out a contrastive study.(3) Based on Midas-Civil bridge structure analysis software, three-dimensional numerical models for bridges are built according to above results; piers are stimulated using elastic-plastic fiber. The author simulates the dynamic response of bridge examples under 40 natural seismic waves by nonlinear time-history analysis and analyzes the seismic fragility of damages of key cross sections in two modeling.(4) By comparing the two seismic fragility curves, it is not hard to find that the exceedance probability of continuous rigid frame bridge in collapse state designed based on AASHTO s below that designed based on Guidelines for Seismic Design of Highway bridges 2008. This is because AASHTO has set more specific provisions on ductility of pier structure, which bring the ductility into full play.