大跨铁路梁桥最大悬臂阶段的静风安全性分析

Aerostatics Safety Analysis of Long-span Railway Girder Bridge at the Maximum Cantilever Stage

在桥梁挂篮悬臂浇筑施工过程中,风荷载与桥梁结构的相互作用是一项工程风险因素。为评估桥梁挂篮悬浇施工过程中结构的抗风安全性,同时为桥梁抗风设计提供有效依据,以某大跨铁路连续梁桥为背景,基于CFD数值模拟结合规范建议公式确定了桥梁关键截面的三分力系数,而后采用Midas Civil建立了考虑桥梁施工全过程的有限元模型。针对主梁最大悬臂阶段将均匀对称、非均匀对称和龙卷风荷载分别与对称及非对称施工荷载工况组合,将结构预存状态与静风荷载效应叠加,以此全面分析主梁最不利施工阶段的静风安全性。结果表明:静风荷载引起主梁横向位移最大值可达到6.98 mm,竖向位移最大值可达到5.03 mm,龙卷风工况对结构位移最为不利;各关键位置应力最大值,最小值均出现在对称均匀加载工况,对称均匀加载工况对结构应力最为不利。为确保结构安全建议在桥梁挂篮悬臂浇筑施工过程中,考虑风荷载效应的影响。

During the traveler cantilever casting construction of bridge,the interaction between wind load and bridge structure is an engineering risk factor.In order to evaluate the wind resistance safety of the structure during the cantilever casting construction of the bridge,and provide an effective basis for the wind resistance design of bridge,a large-span railway continuous girder bridge was used as the background.Based on the CFD numerical simulation combined with the tormual suggested by the code,the coefficient of tri-component of the key section was detremined,then Midas Civil was adopted to establish a finite element model considering the whole process of bridge construction.For the maximum cantilever stage of the main girder,the uniform symmetric,non-uniform symmetric and tornado loads were combined with the symmetric and asymmetric construction load conditions.The combination superimposes the pre-existing state of the structure and the static wind load effect to comprehensively analyze the aerostatics safety of the most unfavorable construction stage of the main beam.The results show that the maximum lateral displacement of the main girder caused by static wind load can reach 6.98 mm,and the maximum vertical displacement can reach 5.03 mm.Tornado conditions are the most unfavorable to the structural displacement.The maximum and minimum valnes of stress at each key position appear in symmetrical and uniform loading conditions,which is the most unfavorable to structural stress.In order to ensure the safety of the structure,it is recommended to consider the effect of wind load during the traveler cantilever casting construction of bridge.