The Analysis Of Initial Stress And Separation Problem Of Concrete-filled Steel Tube Arch Bridge

Because of its merits of high carrying capacity, upstanding plasticity and toughness,construction convenience, better economic effect and better fire performance, the concretefilled steel tube bow string arch bridge is one of the bridge structures that have broadprospects for development. Along with the applying of concrete-filled steel tube technology inbridge engineering,many problems are exposed, the initial stress and separation are the mostcommon problems. These problems have brought a negative impact to the development ofCFST arch bridge. So it is necessary to summarize and analyze the existing problems in orderto take effective measures to avoid these problems during the new bridge design andconstruction.But this kind of bridges has a short development period in China, and the aspectsare studied insufficiently. The situation will bring the adverse effect to the concrete filled steeltube string arch bridge’s development. The paper study GaoYang bridge with the universalFEM software ANSYS and build different3-D finite element models to study the influence ofthe displacement, stability, dynamic characteristics of arch bridge by the initial stress andseparation problems.1) In construction of Most of CFST long-span arch bridge, the main methods arenon-bracket construction technology or the swing technology. Under these methods, beforethe formation of CFST arch bridge, steel tube will withstand the weights of itself and the wetconcrete, this will cause the initial stress of the steel tube inevitably. The initial stress forcesthe steel tube to prior reach the yield point of material, which will affect the bearing capacityof CFST arch bridge. The paper build ANSYS3-D finite element model to consider theinfluence of dynamic performance of CFST arch bridge by initial stress,and study the effect ofdegree of initial stress,steel ratio and so on.2)Because the effect of the load, difference in temperature, shrinkage and creep ofconcrete, construction quality and so on, the large span CFST arch bridge have differentdegrees of separation problem, the actual mechanical behavior of CFST arch bridge should bebetween complete debonding and complete bonding. The paper build different3-D finiteelement model according to complete debonding and complete bonding. Firstly, the staticforce, stability, dynamic characteristics of the bridge in the state of the two stations are analyzed in the paper. The results indicated that separation reduce structural stability andstiffness, but the separation effects on dynamic characteristics are very small. The actualCFST arch bridge are generally not achieve fully the extent of complete debonding. So theconception of separation ratio are used to describe the part debonding phenomenon of CFSTarch bridge. Besides the degree of the effect has the relationship with separation ratio, steelratioan and height of truss.Finally the paper proposed some effective measures in common use to prevent and curethe initial stress and separation problem in combine with the analysis result. The conclusioncould offer viable reference of this type of bridge design and construction, and provided forsome effective basis of health inspection and maintenance for CFST arch bridge.