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

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.