大跨度板桁加劲梁桥简化建模方法研究

摘要

大跨度板桁加劲梁桥的抗风研究需建立全桥模型分析桥梁的动力特性,针对全桥精细化有限元模型单元数多,计算费时等特点,基于桁架和正交异性板的连续化等效板厚公式,将板桁加劲梁的正交异性板简化为桁架,使其成为空间桁架结构.为了保证空间桁架的力学性能与板桁加劲梁等效,分别确定桁架各杆件的截面特性,形成新的简化建模方法.最后以主跨跨径为1 386 m的某板桁加劲梁悬索桥为例,分别建立精细化模型和简化模型,通过分析动力特性对简化建模方法进行验证.结果表明:精细化模型与简化模型的自振频率吻合良好,简化建模方法能满足动力特性的分析要求.%To study wind resistance of the long span bridge with plate-truss stiffening girder,the whole bridge model is built to analyze the dynamic characteristics.In view of the characteristics of high precision finite element model with multiple elements and low computational efficiency,the orthotropic plate of plate-truss stiffening girder is simplified to a truss to form a space truss structure based on the formulas for continuous equivalent plate thickness of the truss and the orthotropic plate.In order to ensure the equivalency of the mechanical properties between space truss and plate-truss stiffening girder,the cross-section characteristics of each bar of the truss are calculated respectively,then a new simplified modeling method is formed.Finally,the high precision model and simplified model are built with reference to a suspension bridge of 1 368 m span with plate-truss stiffening girder.The simplified modeling method is verified by analyzing dynamic characteristics of the suspension bridge.The results show that the natural vibration frequency of the high precision model agrees well with that of the simplified model,and the simplified modeling method meets the requirement of dynamic property analysis.