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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。
When the joints of the long-span composite truss girder bridge are all welded, there is a phenomenon of local stress amplification, which may affect the fatigue performance of the bridge. According to the auspicious bridge in Haihe, Tianjin, the fatigue behavior of the welded joints was analyzed by the hot spot stress method based on the finite element software ANSYS. The preliminary analysis results show that the results obtained by ANSYS-built Smart partitioning method and high-order element are accurate enough, stress concentration is not generated in the joint welds, and the model boundary conditions have a great influence on the results. Through the comparison and analysis of different working conditions, it is found that the shear force and bending moment of the diagonal webs at the node have some influence on the stress at the corner outside the joint plate, but the impact is less than the axial force. Through the finite element analysis of the local stress of the welded joints of the bridge, it is proved that the stress level of the key parts of the joint plate under the actual load of the full bridge is within the safe range, which provides a reliable basis for the design and construction of the structure and can be used for future Fatigue analysis for reference.