The Research On Fold Option And Coustruction Control Of Mulit-span-short Tower Cable-stayed Bridge

Multi-span-short tower cable-stayed bridge is a new bridge type between beam bridge and cable-stayed bridge ,the requirements of its construction is high. Short towers cable-stayed bridge although started quite late, but it has many advantages, which is developing very quickly. The structure system of multi-span-short tower cable-stayed bridge is complex, high times super statically determinate and construction process is complex, the internal structure of construction stage and the linear constantly change with construction state . So the effective controlling to construction can ensure the structure construction process safety and take the internal force of structure and the linear of structure comply with the design of requirements ,fixed various influences of the target of bridge error of parameters, ensure the structure construction process safety and take the internal force of structure and the linear of structure comply with the design of requirements. Closure option of short towers cable-stayed bridge has direct impact to its bridge state ,it is particularly important to short towers cable-stayed bridge .This paper use the West river bridge as project background ,setting up the finite element model to researching some details as follows:(1) Introduces briefly the origin, the development situation, Structure and mechanical characteristics and some problems existing in the development of short tower cable-stayed bridge .Also summarize the construction control of the short tower cable-stayed bridge.(2) Working out three closure options establish a finite element model of West river bridge , through the test calculate method to determine the sequence of three fold pushing force and corresponding counterweight imbalance, and compared with the structural internal force of the top thrust and not add it.(3) Comparative analysis in three fold scheme of the structure deflection and stress condition after loaded and phase constant bridge five years later ,to get more reasonable fold sequence. Then select one of the optimal order , When the piers in plastic stage and elastic stage, of some analyses force of the piers.(4) To do sensitivity analysis of the main structure influencing parameters of large span bridge in construction process, include :girders density,Stay-cables structure,rigidity of structure and loss of prestress and so on. Get the influence of the girder bridge condition and main alignment design parameters and the secondary design parameters, and using mathematics method (orthogonal experiment design method) to demonstrate it. The conclusions can provide some references for the same type bridge in design and construction .Using Midas/civil model , analyzed the influence of local temperature and the overall temperature to cantilever structure of construction stage before fold .(5) It introduces the present condition forecasting method, using least-square method to distinguish the parameters of main design parameter .