Calculation Of Stress-free Configuration And Application Of Steel Truss Girder Cable-stayed Bridge

In recent years, with the rapid development of China's steel smelting technology and construction technology of girder beams, steel truss girder cable-stayed bridge using truss as main girder sprung up in abundance, especially the long-span bridges in the mountains and across the river grow with each passing day.At the same time, due to the complexity of girder beams construction, variety of structure bars, a set of systematic construction control system is needed to ensure the geometric linear and internal force state after the bridge is finished. This paper takes unstrained geometry method using in the construction control of steel truss girder cable-stayed bridge as main lines, some research has been done and the corresponding conclusions are obtained as follows:(1)This paper introduced the general research situation about construction control of cable-stayed bridge, describes the calculating theory of unstrained geometry control method, makes elaboration for the geometric nonlinear problem of long-span bridges, studies the difference as well as relationship between fabrication geometry, assembled geometry and unstrained geometry, then the conclusion that assembled geometry cannot replace fabrication geometry is obtained, while the initial calculation point coordinates of theoretical calculation model should be point coordinates of fabrication geometry.(2)The calculation method for determinated the steel girder nodes, segmental dividing point and unstrained position of anchor is stated, the precise calculation principles, methods, steps and processes of steel truss girder unstrained geometry is studied systemically, as well as the considering factors and principles of gusset plate types combination. For the problem that calculating the unstrained geometry of concerned girder, the calculation method of adjacent beam opening value, unity of gusset plate types and the relationship between screw hole of gusset plate and opening value is studied and analyzed systematically, the control system of calculation of girder unstrained geometry.(3)By making further study to the stiffness equivalent analysis of steel truss girder, the stiffness correction coefficient of plane brace resulting from theequivalence between Pratt,Warren truss pace model and plane truss, single beam is obtained, as well as it is relation curve and fitting formula with truss height,internode length, the plane model after the equivalence reduces the element number and node number of model, significantly improving the efficiency of analysis and calculation.(4)The finite element numerical model of zhongjian river bridge is established,providing a simple processing method for temporary consolidation, boundary conditions, loading of steel truss girder cable-stayed bridge. Precise control system of girder unstrained geometry is used in this bridge, thus the gusset plate,that has less types, unified specifications, convenient construction and be easy to manage,is obtained.(5)Basing on the sensitivity analysis to the structural design parameters, a conclusion that the sensitive degree from high to low are in order of girder weight,cable weight, temporary construction load, elastic modulus of girder, elastic modulus of elastic modulus is reached; at the same time, as the measured geometry after the closure of middle span girder coinciding well with the theoretical geometry, the success of the practice that applying the unstrained geometry control method to steel truss girder cable-stayed bridge is proved.