Analysis Of Ultimate Load-carrying Capacity Of Long Span Cable Stayed Bridge With Separate Steel Box Girder

The second Wuhu Yangtze river road bridge with 806m central span length is a great cable-stayed bridge of separate steel box girder, four cable plane structure characteristics, these characteristics making each single girder with great independence as it suspended by two cable planes, as the same time two girders with good entirely as they connected by cross beams in certain distance. This paper studied the ultimate load-carrying capacity of the second Wuhu Yangtze river road bridge and the parameters affecting the ultimate load-carrying capacity of the structure, in order to clarify the mechanism of ultimate load-carrying capacity of the cable-stayed bridge with separate steel box girder, mastering the ultimate load-carrying capacity behavior of the bridge and the safety reserve of the structure from the overall level. These works could not only provide design reference for the same type of bridge, but also give the basis for the design of the second Wuhu Yangtze river road bridge healthy monitoring system.The main research work and conclusions are as follows:1. The finite element model of the second Wuhu Yangtze river road bridge was built to analyze the elastic buckling of the structure as well as the effect of the stiffness of the cross beams to the elastic buckling of the cable-stayed bridge of separate steel box girder. The result showed that the first modal of the buckling is inside buckling, increasing the stiffness of the cross beams will increase the overall stability of the structure.2. The ultimate load-carrying capacity of the second Wuhu Yangtze river bridge is calculated with material nonlinear and geometric nonlinear considered. The influence of the nonlinear factors of the structure to the ultimate load-carrying capacity is discussed and the failure path is analyzed. The results point out that the stay-cables of mid-span yield leading to the failure of the structure under the whole span load; therefore the ultimate load-carrying capacity of the cable-stayed bridge is controlled by the material nonlinear of the stay-cable.3. This paper analyzed emphatically the influence of parameters on the ultimate load-carrying capacity of long span cable-stayed bridge with separate steel box girder. Compared the ultimate load-carrying capacity and the Integral internal force of three kinds of structural system of cable-stayed bridge; discussed the effect of different load distribution on the ultimate load-carrying capacity of structures; analyzed the transverse distribution of the cable force under the single uniform live load; finally, the influence of structural design parameters on the ultimate load-carrying capacity is discussed in detail. The results show that the performance of the floating system and half floating system are very close, the ultimate load-carrying capacity of the rigid frame system is the best. The distribution of distributed load has obvious effect on the ultimate load-carrying capacity. The stress increment of the four cables is basically linear in the critical section under the single uniform live load. Therefore, the transverse distribution of the cable force under the ultimate load is uniform, separate box girder is still maintained in a good working state. The spacing of cross beams had an important influence on the ultimate load-carrying capacity of the structure under the asymmetric load. By changing the distance of the auxiliary pier to the side pier, the internal force and deformation of the structure near the auxiliary pier are obviously influenced, and the ultimate load-carrying capacity of the structure is not obvious.