地裂缝活动对城市连续梁桥作用的力学分析

A mechanical analysis on the effect of ground fissure activity on urban continuous beam bridges

由于城市交通的工程线型特点,其建设与运维无法避免会受到地裂缝活动的影响。基于MIDAS GTS NX建立一个三跨连续梁桥正交跨越地裂缝的有限元模型,分析在地裂缝不同沉降量下连续梁桥箱梁及墩台的位移场和应力场变化规律。结果表明,箱梁结构在不同沉降量条件下的主要差异沉降区范围基本相同,且与地裂缝影响带宽度基本等同,即上下盘各20 m长,共计40 m;箱梁的变形可分为三段:抬升区、不均匀沉降区和整体沉降区;地裂缝的上盘箱梁表面受压,而下盘箱梁表面受拉更为明显,处于桥墩位置处的箱梁应力显著增加,箱梁结构的破坏易因拉应力的陡增而发生在地裂缝的下盘桥墩处。地裂缝影响范围内的中跨两侧墩台产生显著的差异位移变化量,而地裂缝影响范围外墩台所受影响较小。研究成果可为已建和规划中的跨地裂缝连续梁桥的致灾机理研究及灾害防治提供重要参考。

The construction and operation of urban transportation cannot avoid the influence of ground fissure activity due to the linear characteristics.The finite element model of a three-span continuous beam bridge orthogonally crossing ground fissure was established based on MIDAS GTS NX.The variation of displacement fields and stress fields of the continuous beam bridge’s box girder and pier under different settlement of ground fissure were analyzed.The results show that under different settlement conditions,the differential settlement areas of the box girder structure remain the same,and the width is basically the same as that of the influence zone of ground fissure:both the longth of hanging wall and foot-wall are 20 m,40 m in total.The deformation of the box girder can be divided into three sections,that is,uplift area,differential settlement area,and overall settlement area.The surface of box girder at hanging wall is mainly subjected to compressive stress,while that at footwall is mainly subjected to tensile stress.The stress of box girder at the position of pier increases significantly,and the failure of box girder structure tends to occur at the footwall pier of ground fissure due to the sudden increase of tensile stress.The differential displacements of bridge piers on both sides of the mid-span within the influence range of ground fissure significantly change,while the piers outside the influence range of ground fissure are less affected.The research results can provide an important reference for the research on the disaster-causing mechanism and disaster prevention of the existing and planned continuous beam bridges.