箱桁组合梁铁路斜拉桥动力特性有限元建模方法研究

摘要

为实现箱桁组合梁铁路斜拉桥动力特性的精准模拟计算，对箱桁组合梁开口断面斜拉桥空间杆系模型、空间板梁组合模型和空间板壳模型3种有限元建模方法进行研究。以某跨径布置为（98＋140＋406＋406＋140＋98） m的三塔双主跨箱桁组合梁铁路斜拉桥为背景，采用子空间迭代方法对比分析了不同模型的模态特性，并在此基础上计算了不同模型主梁单位长度的等效质量及其惯性矩。研究结果表明：3种模型计算得到的模态分析结果基本吻合，空间板梁组合模型和空间板壳模型得到的频率及主梁等效质量基本相同，但空间杆系模型不能准确得到高阶侧弯模态的主梁等效均布质量。作为特例，进一步对无桁架钢箱梁开口断面斜拉桥的动力特性进行分析，结果表明：空间板梁组合模型和空间板壳模型吻合良好，但空间杆系模型得到的1阶扭转模态下的主梁等效均布质量惯性矩误差接近9％；桁架对主梁的侧弯基频影响较小，但能提高主梁的竖弯基频和扭转基频，有利于桥梁抗风。%To realize the accurate simulation calculation of the dynamic performance of box‐truss composite girder railway cable‐stayed bridge ,the three finite element modeling schemes of the box‐truss composite girder cable‐stayed bridge with open cross section are studied ,including the spatial bar element model ,combined space plate and beam element model and spatial shell ele‐ment model .A three‐pylon two main spans box‐truss composite girder railway cable‐stayed bridge with span arrangement of (98+140+406+406+140+98) m was taken as the study background . The sub‐spatial iterative method was used to comparatively analyze the modal characteristics of the different models ,and based on w hich the unit length equivalent mass and inertia moment of the different main girder models were calculated .The results of the study show that modal analysis re‐sults gained from the three model calculations are basically consistent , the frequency and main girder equivalent mass gained from the combined plate‐beam element model and spatial shell ele‐ment model are approximate ,nevertheless ,the spatial beam element model could not accurately calculate the main girder uniform equivalent mass of the high‐order lateral bending modes .As an exception ,the dynamic performance of the steel box girder cable‐stayed bridge without truss and with open cross section was analyzed independently .The results of the analysis show that the com‐bined plate‐beam element model and spatial shell element model are in good agreement ,but the in‐ertia moment of the main girder uniform equivalent mass under the first order torsional mode gained from the spatial beam element model reveal an error of 9% .T russ has slight influence on the lateral bending frequency of the main girder ,but can improve the vertical bending frequency and torsional frequency of the main girder ,w hich is favorable for the wind resistant performance of the bridge .