The Test And Theory Research On Structure Behaviour Of Plate-Truss Composite Girder

Cable-stayed bridge is an important structural type of long-span bridge. The plate-truss composite structure, in which the concrete deck and steel main truss co-act together, has come into use in long span cable-stayed bridge for both highway and railway because of its many advantages. But no refrences are available about this kind of bridge, which employed in Wuhu Yangtz River Bridge with both highway and railway because of its functional needs. Bridge engineers want to comprehensively understand its mechanics charactisitic. In view of this, author has adopted many test resrarchs and analysis for its important technicality problems. The test and theory researchs contain following works:(1) In the dissertation, based on the principle of nonlinear continuum mechanics, the geometric nonlinear analysis theory of structure is prescribed thoroughly. The difference between Total Lagrangian Formulation and Updated Lagrangian Formulation are also discussed. Furthermore, the causes of geometric non-linearity in long-span cable-stayed bridges are analyzed. The equivalent modulus of elasticity and the stability functions considering beam-column effect of tower and main girder are deduced in the paper. It is pointed out that S5 in Fleming's stability functions has singularity. At the same time, the methods to cope with various factors of geometric nonlinearity are estabilished.(2) The spatial mechanics model of the cable-stayed bridge, Wuhu Yangtz River, with plate-truss composite beam, which can take the couple function of local and global deformation in to accounts, is set up. The main beam is discreted into finite segment elements of plate-truss composite beam that involve tension, compression, bending, twisting, section distortion, warping deformation, secondary stress of truss, local bending and shear lag effect of deck plate. Based on the thoughts that the total displacement of particles is the sum of the displacements caused by global and local deformation, the displacement model and calculating formulae are formed.(3) In order to investigate static characteristics, dynamic characteristics and rational rigidity of Wuhu Yangtz River bridge. The model test of global structure for Wuhu Yangtz River bridge with reduced scale 1:50 was carried out. Test contents had been containing:stress distribution and spread, secondary stress distribution of main truss member, shear lag distribution of deck plate et al. for construction process and working state of bridge.(4) According to the reduced scale 1:5, on engaging in local model experiment with 7 segment for Wuhu Yangtz River Bridge, a thorough investigation and study has been made for following problems:(a) auxiliary truss property of force bearing; (b) internal force distribution between deck plate and upper chord of truss; (c) shear connector property of force bearing; (d) internal force distribution between lower lateral bracing and railway floor system; (e) secondary stress of main truss member; (f) stress distribu tion of deck plate.(5) The monolithic gusset plate experiment has been completed, its goal was to comprehensively understand fatigue property and stress distribution state of monolithic gusset plate.