单箱大悬臂组合梁桥桁架式横隔板斜撑疲劳研究

Fatigue Study of Inclined Struts of Truss Diaphragms of Long Cantilever Single Box Composite Girder Bridge

为了解单箱大悬臂组合梁桁架式横隔板斜撑的疲劳特性,以沪杭高速公路跨大蒸港主桥(2×75m的钢-混凝土连续组合箱梁桥)为例进行研究。采用ANSYS软件建立该桥全桥的空间有限元模型,对1/4,1/2,3/4跨和中支点位置桁架式横隔板内、外斜撑的两端节点进行疲劳分析。首先采用容许应力法验算斜撑节点疲劳强度是否满足要求,然后采用安全寿命法计算不满足疲劳强度节点的疲劳寿命。分析结果表明:单箱大悬臂组合梁桁架式横隔板斜撑节点应力幅较大,如果采用疲劳强度低的细节,设计使用期内很可能会出现疲劳破坏,在设计中应引起足够的重视。

To understand the fatigue behavior of the inclined struts of truss diaphragms of long cantilever single box composite girder bridge,the main bridge （a steel and concrete continuous composite box girder bridge with span arrangement 2 × 75 m） of the Dazheng Harbor Bridge on Shanghai-Hangzhou Expresswaywas cited as an example and studied.The software ANSYS was used to establish the spatial finite element model for the whole bridge of the bridge and the fatigue analysis of the two-end joints of the internal and external inclined struts of the truss diaphragms of the bridge at the locations of 1/4,1/2,3/4 span and at the intermediate support was carried out.The allowable stress method was firstly used to check if the fatigue strength of the joints of the struts could meet the requirements and then the safety life method was used to calculate the fatigue life of the joints that did not meet the requirements.The results of the analysis indicate that the stress amplitude of the joints of the struts is great.If the details of low fatigue strength are used,the fatigue failure will mostly take place in the designed service period and therefore sufficient importance should be attached to the failure in the design.