三门峡黄河公铁两用桥钢桁梁顶推动力学分析

Dynamic Analysis of Incremental Launching Construction for Steel Truss Girder in Sanmenxia Yellow River Rail-cum-Road Bridge

研究目的:有关钢桁梁顶推施工的研究大多局限于杆系有限元的静力学分析,然而钢梁顶推是一个动态过程,桥墩-钢梁-滑块-滑道梁相互作用成为三维空间体系,力学机制复杂,目前对顶推动态过程的计算分析较为少见.鉴于此,本文采用数值模拟和试验监控相结合的手段,对三门峡黄河公铁两用桥钢梁顶推过程进行动力学分析,以便明确各细部结构的受力状况,为主体结构的安全施工提供技术保障.研究结论:(1)顶推过程中墩身承受交替变化的拉/压应力,初始阶段的拉应力和变形较大,随着向托梁中部顶推,桥墩拉应力和变形减小,易开裂区向弧形帽梁底部扩展;(2)滑道梁的应力和变形随着滑块接近托梁中部逐渐减小且分布趋于均匀,最大应力出现在腹板与加劲肋连接位置;(3)滑块在顶推初始阶段出现类似"爬坡"的现象,与滑道梁接触面的受力、变形不均匀,且存在静-动摩擦系数的转变,导致桥墩在顶推开始时刻承受一定水平力;(4)本文研究可用于指导高墩多跨连续钢桁梁的顶推施工.

Research purposes:The researches on the incremental launching construction for steel truss girder are mostly limited to the static analysis of bar-system finite element.However,the jacking construction of steel beam is a dynamic process,the pier,steel beam,slide block and slipway beam form a three-dimensional space system with complex mechanical mechanisms.At present,the calculation and analysis for dynamic process of jacking construction are relatively rare.In view of this,this paper uses a combination of numerical simulation and experimental monitoring to carry out a dynamic analysis for the jacking process of the steel truss girder in Sanmenxia Yellow river rail-cum-road bridge,so as to clarify the actual mechanical behaviors of the detailed structures and to provide technical supports for the safe construction of the main structures.Research conclusions:(1)The pier body is subjected to alternating tensile/compressive stresses during the incremental launching process,and the tensile stresses and deformations in the initial stage are relatively large.With the jacking towards the middle of the concrete joist,the pier tensile stresses and deformations decrease,and the crack-prone zone extends to the bottom of the arc-shaped cap beam.(2)The stresses and deformations of the slipway beam gradually decrease as the slide block approaches the middle of the concrete joist,and the distribution tends to be uniform.The maximum stress occurs at the connection position of the web and the stiffener.(3)At the initial stage of the incremental launching,the slide block experiences a phenomenon similar to"climbing",the contact surface between the slide block and the slipway beam is uneven in force and deformations,which results in the bridge pier bearing a certain horizontal force at the beginning.(4)The research results can be used to guide the incremental launching construction of continuous steel truss girder with high piers and long spans.