三主桁斜边桁空间桁架公铁两用桥节点局部应力分析

郑州黄河公铁两用桥主桥采用无竖杆的三主桁斜边桁的空间桁架形式,其节点构造及受力复杂,为了解该新型节点板处结构的局部受力,采用有限元软件对该主桥第2联有代表性的典型节点(E20)进行局部应力分析,并探讨局部模型边界处理方式对计算结果的影响。计算结果表明:在荷载组合仅考虑主力组合情况下,与节点E20相连的各构件的Von Mises应力较大,但未超过Q370qE钢材屈服强度的要求,结构强度满足安全需要;仅以整体分析得到的变形或内力作为局部分析模型的边界条件进行局部受力分析,所得结果与利用圣维南原理计算得到的结果有较大偏差;应当严格按照圣维南原理的要求进行局部边界条件施加才能得到合理的结论。

Analysis of Local Stress of Joint of a Spatial Steel Truss Girder Rail-cum-Road Bridge with Three Main Trusses and Inclined Side Trusses

The main bridge of Zhengzhou Huanghe River Rail-cum-Road Bridge employs the spatial steel truss girder with three main trusses and inclined side trusses without vertical members and the structural formation and force conditions of the joints of the truss girder are complicated.To understand the local force conditions at the structure of the new type joint plates of the girder,the finite element software was used to analyze the local stress of the typical joint(E20) of the second unit continuous girder of the main bridge and the influences of handling ways of boundary conditions for the local model on the calculation results were discussed.The results of the calculation show that when the principal force combination is considered only in the load combination,the Von Mises stress of various members connected with the joint E20 is great,but is not greater than the yield strength of Q370qE steel and the structural strength can satisfy the safety requirement.When the local stress is analyzed by using the deformation or internal force obtained from the global analysis as the boundary conditions for the local model only,the results of the analysis have considerable difference with the calculation based on the Saint Venant′s principle.It is therefore required that the boundary conditions should be provided strictly in accordance with the Saint Venant′s principle in order to come to rational conclusions.