板桁梁抗扭惯性矩的计算方法

抗扭惯性矩是考察大跨度板桁梁受力性能的重要参数，但板桁梁精细化的有限元建模分析较复杂，结构模型试验成本较高，简洁可靠的计算分析方法是更好的选择。首先，针对桁架结构，基于剪切刚度相等原则，提出了考虑弦杆框架效应的桁架等效板厚度的解析表达式。其次，考虑桥面板与U肋在水平方向剪切变形的一致性，改进了正交异性板的等效板厚度的计算公式，给出了板桁梁扭转惯性矩的解析公式。最后，以实际板桁梁为例，采用精细化的有限元模型验证了该文计算方法的正确性。结果表明，提出的板桁梁抗扭惯性矩的计算方法具有较高的精度。

A COMPUTATIONAL METHOD OF TORSIONAL INERTIA FOR PLATE TRUSS GIRDERS

The torsional inertia is an important parameter to measure the mechanical performance of long-span plate truss girders. As a detailed finite element model of plate truss girders is complex and the model test is costly, a succinct and reliable computational method is a better choice. First, the analytic formula of equivalent plate thickness of the main truss, taking into account the chord framing effects of the truss structure, was derived based on the shear stiffness equality principle. Secondly, the analytic formula of equivalent plate thickness of the orthogonal plate was improved based on the consistency of horizontal shear deformation between the bridge panel and the U-rib, and the calculation formula of torsional inertia of the plate truss girder was presented. Finally, the detailed finite element model of a practical plate truss girder was taken as an example to prove the validity of the computational method. The results show that the proposed method for calculating the torsional inertia of the plate truss girder has a high degree of accuracy.