钢桁腹式混凝土组合箱梁翼板纵向应力的计算方法研究

Research on calculation method of longitudinal stress on flange plate for concrete composite box girder with steel truss webs

为研究钢桁腹式混凝土组合箱梁翼板纵向应力沿横桥向的分布情况,运用有限元软件ANSYS建立一座35 m等截面简支钢桁腹式混凝土组合箱梁的有限元模型,考虑斜向腹杆杆力作用会使翼板产生附加轴力及相应的附加应力,故利用能量变分法原理推导出组合箱梁的翼板纵向弯曲应力和纵向附加应力计算公式,并据此探讨适用于计算组合箱梁的翼板纵向应力的方法。将有限元值和理论值进行比较,吻合程度良好。研究结果表明,组合箱梁的下翼板纵向应力可采用纵向弯曲应力计算公式进行计算;为获得组合箱梁的翼板附加轴力,可将组合箱梁的钢桁腹杆和混凝土纵梁取出,认为两者通过节点构造共同构成平面桁架,翼板附加轴力即为平面桁架的弦杆杆力;组合箱梁的上翼板纵向应力可通过纵向弯曲应力和经修正的纵向附加应力叠加获得。

In order to study the transversal distribution of longitudinal stress on the flange plate of concrete composite box girder with steel truss webs,the FEM of a real bridge of a 35 m-long constant section simply supported concrete composite box girder with steel truss webs is established by using the finite element software ANSYS,in consideration of the additional axial force and corresponding additional stress on flange plate generated owing to the action of oblique steel truss webs members' rod forces,the formulas for calculating the longitudinal bending stress and longitudinal additional stress on flange plate of the composite box girder are derived accordingly.Then the method for calculating the longitudinal stress on flange plate of the composite box girder is discussed.The finite element results show good agreement with the theoretical results.The results of the study show that:for lower flange plate of the composite box girder,the longitudinal stress can be calculated directly by the formula for calculating longitudinal bending stress;in order to obtain the additional axial force on flange plate of the composite box girder,the steel truss webs and stringers of the composite box girder can be taken out separately,it is considered that both of them form plane truss systems,and the additional axial forces on the flange plate are the rod forces of the chords on the plane trusses;for upper flange plate of the composite box girder,the longitudinal stress can be calculated by adding together the longitudinal bending stress and modified longitudinal additional stress.