Research Of Key Technique In Construction Control Of P.C. Cable-stayed Bridge

The cable-stayed bridge is an indeterminate structure with high degrees,and it is hard to design and construct this bridge. Because cable is the key component of cable-stayed bridge,the cable tension directly decides the security and economical efficiency of the structure. For the segmental-construction P.C. cable-stayed bridge,difference in temperature,shrinkage and creep sophisticatedly affect the course of its construction. After closure,with the strength of concrete,the adjustable range of internal force and configuration is narrow. So,rigorous control of construction is the guarantee of achieving design objective. Basing on WenHui Bridge (the cable-stayed bridge),optimization of cable tension under dead loads,control of the course of cantilever casting concrete,and Spatial analysis of the pylon and gird during construction were discussed in this paper.Seek the sound cable tension to aim at minimum of maximum stress by the method of FEM analysis combined with optimization. During optimization,use virtual lamina beam element to analyze the structure. The result of optimization of the cable tension of WenHui Bridge shows this method is easy,effective and applicable. According as distortion harmonious condition of traction cable's anchorage on cable-suspended traveler,increasing amount of cable tension during casting concrete was computed,and under every key operating condition of casting concrete,traveler's frontend elevations were educed. We seriously controlled WenHui Bridge's course of cantilever casting concrete by this method,which assured that the bridge's construction went on successfully. And then,it was discussed how to simulate the effect of prestressing force in spatial analysis. Equivalent node load can well simulate the effect of prestressing force,and the lost of prestressing force can be well considered by dividing it into two sort.According as the field situation,three-dimensional model was set up to analyze the stress state during building pylons of WenHui Bridge with degenerated solid elements. The measured result of pylon's stress was compared with theoretical value. The comparison shows that non-stress ingredient could be mostly excluded by deducting initial value,and that the modified test-result of stress could well display the real stress state.Three-dimensional model was also set up to analyze the structure's distortion,cable tension and stress state during the segmental-construction of WenHui Bridge's girder with degenerated solid elements. The effect of prestressing force and concrete's creep were considered in analysis.The results of spatial analysis and planar analysis were finely compared with the measured value. By comparison,some conclusions are obtained:model's errors are in evidence,when using planar model to analyze the cable-stayed bridge in building,especially for girder's distortion;the transverse distributing of direct stress along axis of bridge is apparent;and the method of planar analysis can't satisfactorily solve asymmetry of stress's transverse distributing.