大跨组合桁梁桥全焊接节点局部应力有限元分析

大跨组合桁梁桥节点采用全焊接形式时,存在局部应力放大现象,可能影响桥梁疲劳性能。针对天津海河吉兆桥,基于有限元软件ANSYS采用热点应力法对焊接节点的疲劳性能进行分析。初步分析结果表明,采用ANSYS自带的Smart划分方式及高阶单元进行有限元分析所得到的结果具有足够的精度,节点焊缝处未产生应力集中现象,模型边界条件对结果影响较大。通过不同工况的对比分析,发现节点处斜腹杆的剪力和弯矩作用对节点板外侧转角处的应力有一定影响,但与轴力相比影响程度较小。通过对该桥焊接节点的局部应力有限元分析,证明节点板关键部位在全桥实际荷载作用下的应力水平处于安全范围内,为结构的设计施工提供可靠依据,并可为今后该类节点的疲劳分析提供参考。

LOCAL STRESS FINITE ELEMENT ANALYSIS OF ALL-WELDED JOINT IN LONG-SPAN COMPOSITE TRUSS GIRDER BRIDGE

When joints in long-span composite truss girder bridges are welded,the amplification effect of local stress may influence the fatigue performance of the bridge. Based on the engineering background of Tianjin Jizhao Bridge,a fatigue analysis of welded joint is conducted by means of finite element program ANSYS and hot spot stress method.The preliminary analysis shows that sufficient accuracy can be guaranteed when the Smart mesh method and high-order element provided by ANSYS are adopted. The stress amplification effect is not evident in the region adjacent to the weld. The boundary condition of the model may significantly influence the simulation results. Based on the comparative analysis under different load cases,it is found that the shear force and bend moment on the diagonal web member has some influence on the stress distribution of joint plate,but less than the influence of axial force. It is proved that the key part of joint plate is in a safe stress range under actual load. The present study can provide reliable basis and reference for the engineering and similar analysis in the future.