Stablity Analysis On Long-span Road-Rail Cable-Stayed Bridge

On account of the engineering background of a long span road-rail cable-stayed bridge, the stability was studied through theoretical analysis and finite element calculation. The distribution law of the stability of long span road-rail cable-stayed bridge was obtained, thus providing technical reference for future design. The works which had been completed in this thesis were shown below:(1) The development and structural features of road-rail cable-stayed bridges were elaborated, with the structural stability theory, method and the finite element theory of cable-stayed bridges described. Moreover, the safety factor standards of cable-stayed bridge stability are discussed in detail.(2) A large-scale finite element software, Midas Civil, was adopted to build a finite element model of the long span road-rail cable-stayed bridge. The stability of the construction state and completion state were also analyzed respectively. According to the calculation results, the trend of stability safety factor and buckling modes of the long span road-rail cable-stayed bridge were obtained. Results show that global stability problems were most critical in the completion state, while the local stability problems prone to occur in the construction state.(3) According to the equation of flexural compression members in the Design Code for the Steel Structures GB50017-2003and the Code for Design on Steel Structure of Railway Bridge TB10002.2-2005, the stability of local members were analyzed in the three typical construction stages, maximum double-cantilever stage, largest single cantilever stage and completion state respectively. It presented that numerical results obtained by theoretical formula and analysis results of the second type of finite element method for completion stability were in good agreement.(4) Based on the finite element model, the influences of the main truss type, the main truss height, the stiffness of pylon and the cable area were considered separately on the stability of the construction state. For the finite element model, considering the effect of changing construction methods on the construction state stability, results show that a significant impact on the stability of the construction state could be produced by changing in construction methods.(5) According to the finite element model, taking into account the influence of cable faults in different positions in the three typical construction stages, maximum double-cantilever stage, largest single cantilever stage and completion state respectively, it could be achieved that in a typical construction state, cable faults had an impact on the stability and it differed with different positions. Side cable faults had most obvious effect on the stability and stress performance of the long span road-rail cable-stayed bridge, thus requiring special attention on design, construction and maintenance to ensure safety.In conclusion, based on the finite element model of a long span road-rail cable-stayed bridge, its first and second kind of stability law were obtained, with the impact of design parameters on the construction stage and the stability of completion state considered, providing certain reference for future design of long span road-rail cable-stayed bridges.