Research On Long-term Deflection Control Of The Long-span PC Continuous Rigid Frame Based On Load-balancing Method

Long-span continuous rigid frame bridges has developed rapidly in recent years for its advantages of handy construction, economical cost, reasonable internal force and comfortable driving. However, excessive deflection in mid-span is a widespread problem of the rigid frame bridges,it is very meaningful to study how to control long-term deflection of long-span rigid frame bridges.In this paper, the load-balancing method is applied to the deflection control after analyzing the main factors influencing the deflection and the relationship between the internal force and displacement,Studying how to control long-term deflection of long-span rigid frame bridges.1. Analyzing the causes of excessive deflection based on Finite Element Analysis, prestress, box girder rigidity, first time loading age of element, shringkage and creep model are studied to compare their influences on deflection.Then, the amount of prestressed reinforcements,internal force under cantilever stage,internal force and displacement under completion stage and long-term displacement of rigid frame bridges are analyzed to find their relationship.2. In order to explore the application of the load-balancing method, The prestressed reinforcements are redesigned on the basis of the load-balancing theory, the internal force and long-term displacement are compared with the original design,and the method of controling deflection based on the load-balancing method are proved feasible.3. The combination of load-balancing method and light-weight concrete is used to control the deflection. Designing the prestressed reinforcements according to the load-balancing method and using light-weight concrete in mid-span,the results are compared with the original design and the design of using load-balancing method only.The feasibility and advantage of the method discussed above are proved.