顶板横向预应力作用下连续刚构的横向受力分析

Analysis on Transverse Force of Continuous Rigid-Frame Bridge under Transverse Prestressing Forces

连续刚构桥梁截面为宽箱薄壁梁,该类截面特点为顶面宽、悬臂长、腹板间距大,因此截面顶板横向受力复杂,易出现纵向裂缝。以某高速公路中连续刚构桥为研究对象,通过有限元方法分析了桥梁纵向几个典型横断面在恒载、横向预应力及车辆偏载工况作用下箱梁顶板横向受力性能的变化情况。结果表明,横向预应力显著降低了截面顶板的横向拉应力,横向预应力对桥梁截面悬臂部分受力改善很大,而对箱室中间部分受力性能影响很小;横向预应力使原本在恒载作用下的受拉部分变为受压状态,且增强了桥梁横向整体刚度;横向预应力有效削弱了车辆偏载作用下箱梁顶板在腹板处的拉应力峰值,同时可以对外荷载进行有效分配,改善箱梁顶板整体受力;合理设置横向预应力钢束间距,可以使横向预应力分布趋于均匀,避免出现应力薄弱处,减少裂缝。

Continuous rigid-frame bridge section adopts wide-box thin-walled girder,which is characterized by the wide top slab,long cantilever and large web spacing.Therefore,the transverse force of the section top slab is complex where is easy to appear longitudinal cracks.In this paper,relying on a continuous rigid frame bridge,the finite element method is used to analyze the variation of transverse mechanical properties of the top slab of box girder under the conditions of dead load,transverse prestressing and partial load of vehicle.It is revealed that the transverse tensile stress of the section top slab is significantly reduced by the transverse prestressing.The results show that the transverse prestressing has a great impact on the stress of the cantilever section of the bridge,but has minor effect on the stress performance of the middle section of the box chamber;the transverse prestressing changes the original tension part due to the action of dead load into the state of compression and enhances the overall transverse stiffness of the bridge;the transverse prestressing can effectively weaken the peak tensile stress of the box girder top slab at the web under the action of partial load,and can effectively distribute the external load to improve the overall stress of the box girder top slab;and reasonable spacing of transverse prestressed steel bundles can make the distribution of transverse prestressing tend to be uniform,avoid stress weakness and reduce cracks.