悬索桥主缆时变可靠度研究

Research on Time-variant Reliability of Main Cable in Suspension Bridge

悬索桥服役期内由于长期暴露在潮湿的大气环境中,极易受到大气、风雨的侵蚀,导致主缆承载力发生退化,会严重影响桥梁运营安全,需要评估腐蚀后主缆的可靠性。文章以某悬索桥为工程实例,建立了Midas Civil有限元计算模型,得到了主缆控制截面恒载和车辆荷载的荷载效应。根据主缆失效模式建立了极限状态方程,计算了主缆抗力年平均损失率为0.2%~0.4%时主缆控制截面的时变可靠度指标。研究表明,当主缆抗力退化较快时,运营80 a主缆的可靠度指标低于规范值,在设计时应采取防护措施降低运营期间主缆的腐蚀程度,以延长主缆的使用寿命。

During the service period of suspension bridge,due to long-term exposure to humid atmospheric environment,it is extremely vulnerable to atmospheric,wind and rain erosion,resulting in the degradation of the bearing capacity of the main cable,which will seriously affect the safety of bridge operation.It is necessary to evaluate the reliability of the main cable after corrosion.Taking a suspension bridge as the engineering example,this paper establishes the Midas Civil finite element calculation model,and obtains the load effect of main cable control section constant load and vehicle load.According to the failure mode of the main cable,the limit state equation is established,and the timevariant reliability index of the main cable control section is calculated when the annual average loss rate of the main cable resistance is 0.2% and 0.4%.The research shows that when the resistance of the main cable degrades rapidly,the reliability index of the main cable in operation for 80 years is lower than the standard value,and protective measures should be taken to reduce the corrosion degree of the main cable during operation in the design to prolong the service life of the main cable.