高速铁路下承式钢箱系杆拱结合桥的受力分析

Mechanical analysis of through tied-arch composite bridge on high-speed railway

为了了解下承式系杆拱结合桥的受力性能,根据武广客运专线某140m下承式钢箱系杆拱结合桥,设计制作1个比例尺为18的全桥试验模型,并对桥梁在全桥均布、半桥均布、全桥偏载、半桥偏载和超载共5种工况进行加载试验和分析。研究结果表明:在均布荷载作用下,半桥加载方式引起的竖向挠度约为全桥加载时的2倍;在偏载作用时,重载侧与轻载侧竖向挠度之比小于它们的荷载之比;在受力上,拱肋、系梁和纵梁的半桥均布加载都比全桥均布加载时更不利;对于横梁,端横梁梁端面内接近固结,其他横梁梁端面内接近铰结,面外弯曲问题则可通过采用箱型横梁和加大端横梁截面尺寸等措施加以缓解;刚性吊杆既受轴拉作用,也受弯曲作用,以端吊杆受力最为不利,设计时需引起注意;混凝土板的受力状态以第一系统引起的轴拉作用与竖向荷载引起的弯曲作用为主,采用3%以上的高配筋率时裂缝宽度能得到有效控制。

To understand the force-bearing characteristics of through tied-arch composite bridge,a 1 8 scale model was designed and made according to a 140 m steel box tied-arch composite bridge on Wuhan-Guangzhou passenger special railway.Through the model test of 5 load cases including full-bridge uniform load,half-bridge uniform load,full-bridge bias load,half-bridge bias load and overload,the displacements and stresses of the bridge were analyzed.The results show that the displacement of the bridge under half-bridge uniform load is about twice as much as that of the bridge under the full-bridge uniform load.In the case of the bias load,the displacement ratio of the heavy load side to the light load side is less than that of the corresponding loads.The mechanical behavior of the arch ribs,tied-beams and the longitudinal beams in the case of the half-bridge uniform load are worse than those of the full-bridge uniform load.The ends of the first transverse beam are considered as fixed ends while those of the other transverse beams are more like hinge joints during in-plane bending moment.Adopting box beams and larger cross sectional dimensions,the out-of-plane bending problem of the first transverse beam is solved.The rigid hangers bear not only axial force but also bending moments.Owing to its greater bending moment compared with other hangers,special measures in design are needed for the first hanger.The concrete slab mainly withstands axial tensile force and bending moments under vertical load.Its crack width is controlled effectively if high ratio of reinforcement above 3%is used.