FATIGUE RELIABILITY ANALYSIS OF MULTI-LOAD SUSPENSION BRIDGES USING A NONLINEAR FATIGUE MODEL

摘要

Fatigue is one of the most crucial structural safety issues for suspension bridges subject to railway,highway and wind loading. Fatigue damage within bridge's service life accumulation is a nonlinear process,in which lots of uncertainties are arising from both fatigue loading and resistance. This study presents a framework for fatigue reliability analysis of a multi-load suspension bridge using a nonlinear fatigue model,and the Tsing Ma suspension bridge equipped with Structural Health Monitoring System (SHMS) is taken as a case study. The nonlinear continuum damage mechanics (CDM) model is first introduced and simplified for the fatigue analysis of long suspension bridges,and then a framework is proposed for fatigue reliability analysis using the CDM model. As a main concern of fatigue reliability analysis,the daily sum of m-power stress ranges are estimated in the concerned period based on the measurement data acquired from the SHMS. Finally,the failure probabilities at the end of 120 years are estimated under different assumed future loading scenarios. The results demonstrate that the health condition of the bridge is satisfactory at the end of its design life under current traffic conditions without growth,but attentions should be paid to future traffic growth because it may lead to a much greater fatigue failure probability.