To analyze the spatial mechanical performance and shear lag effect in both longitudinal and transversal direction, a three-span S-curve steel box girder bridge was regarded as research object. The 7-DOF beam element of Midas Civil considering warping displacement and Shell181 element of ANSYS were used for the whole bridge spatial simulation based on FEM theory. By detailedly studing the structure displacement, cross section stress, end reaction, and natural vibration characteristics under different loads, the most unfavorable situation of structure and its stress distribution rule were discovered and summarized. By comparing the calculation results of Midas and ANSYS, it can be known that the shell element model is more accurate than the beam element model when simulating the coupled effect of bending and torsion. In the actual design of structures, the shell element should be used for calculating as far as possible because its result can be more safety. In order to further study the shear lag effect, the ANSYS results of some key cross sections of steel box girder bridge were extracted and the change rules of shear lag coefficient in both longitudinal and transversal direction of the bridge were obtained, which can provide reference for design and calculation of similar bridges in the future.%为分析 S 型曲线钢箱梁桥的空间受力特性和纵横向剪力滞效应,基于 Midas 考虑翘曲变形的七自由度梁单元和ANSYS的Shell181壳单元,对一座四跨S型曲线连续钢箱梁桥进行全桥空间精细化仿真建模,研究其在不同荷载作用之下的结构位移、截面应力、支座反力及自振特性,并找出结构的最不利情况及其应力分布规律.经2种有限元单元的结果对比,可知采用板壳单元模型较之梁单元模型对该类桥梁弯扭耦合效应的模拟更为准确,其各项分析结果更偏安全,实际设计中对该类结构应尽可能采用板壳单元进行建模检算.为进一步研究其剪力滞效应,基于ANSYS计算结果研究了该桥各关键截面顶板的剪力滞效应,得出其剪力滞系数的纵横向变化规律,可为今后类似桥梁的设计提供参考.
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