高速铁路下承式板桁结合梁的受力分析

Force of through Plate-truss Composite Beam on High-speed Railway

为了了解下承式板桁结合梁的受力性能,根据京沪高速铁路上的1座简支下承式板桁结合梁桥,设计制作了1个4节间下承式板桁结合梁模型,并分3个阶段10种荷载工况进行了模型试验,对主桁和纵梁的挠度,横梁的竖向、水平位移,纵、横梁、主桁各杆的应力,混凝土板上的应力、裂缝分布及宽度进行了分析,研究了混凝土板与主桁结点是否直接相连以及制动撑对结构的影响。试验结果表明:主桁的挠度和内力与按平面桁架计算的结果相比相差不大;在桥面系中,最大应力发生在横梁2上,混凝土的受力状态以竖向荷载作用下的弯曲为主;在竖向荷载作用下,制动撑的作用不大,但在水平荷载作用下,制动撑的作用明显;设计时可不考虑各种偏载的影响。

Through plate-truss composite beam is a new-type bridge structure for the longitudinal and transverse beam on floor system to combine with concrete slabs and it will be used widely to the bridge on high-speed railway. To know the force-bearing properties of this structure, a through plate-truss composite beam model with four spaces is designed and made according to a through plate-truss composite beam in simple suppurations on Beijing-Shanghai high-speed railway. Through the model test in 3 stages and including, 10 work cases, the displacements and stresses of main trusses, longitude beams and horizontal beams, as well as stress distribution and the width of fissures in concrete slab are analyzed. The problem of whether main truss links with concrete slab directly and the influence of braking ties on structure are also observed. The results show that displacements and internal forces of main truss are equal approximately to those of plane truss, the max stress on floor system is in No.2 longitudinal beam, the concretes are mainly suffered bent at vertical loads, the role of braking ties can be ignored, and the structure design is not controlled by deflecting loads.