Research On Design Of Longitudinal Prestressed Tendons Of PC Continuous Rigid Frame Bridge

The large-span PC continuous rigid frame bridge has been favored in the field of bridge construction in recent years due to its unique advantages such as convenient construction,low cost,reasonable stress,and smooth driving.With the rapid development of the world economy,PC continuous rigid frame bridges Develop faster.In recent years,some PC continuous rigid frame bridges have had a problem of excessive deflection in the middle of the span after the bridge is built.Therefore,it is of engineering significance to regard the bridge formation state for the purpose of controlling long-term aging deformation as a reasonable bridge state.In view of the reasonable bridge formation status,further research is needed on the prestressed design of continuous rigid frame bridges.Based on the reasonable completion status of PC continuous rigid frame bridge,this paper studies and analyzes the longitudinal prestressed bundle design of PC continuous rigid frame bridge,and mainly completes the following aspects:(1)Reviewing the existing literature of PC continuous rigid frame bridge,this paper summarizes and analyzes the development process and trend of PC continuous rigid frame bridge,describes the common diseases of large-span continuous rigid frame bridge at present,and expounds the research status of prestressed design at home and abroad aiming at the diseases.(2)Relying on the actual project,Midas/Civil is used to analyze the large cantilever state and completed state of two single-leg hollow pier rigid frame bridges respectively,to explore the relationship between internal force state and deflection,and to obtain that increasing the ratio of prestressed bending moment to dead load bending moment is a way to reduce the long-term deflection of PC rigid frame bridges.(3)This paper introduces the application of the zero moment method theory in cantilever prestress design.Based on this theory,a design method of cantilever prestress is proposed in combination with prestress allocation sequence.The characteristics of the method in internal force,stress,displacement and other aspects are analyzed through a cantilever beam example.In addition,the principle of load balance is introduced to configure the prestress of closure section.From the angle of mid-span bending moment contribution and downwarping control,the reasonable configuration length of prestressing force in closure section is discussed by force method and graph multiplication.(4)Based on the characteristics of reasonable bridge state,the prestressed design method proposed in this paper is used to design the longitudinal prestressed tendons of a PC continuous rigid frame bridge,and Midas/Civil is used for analysis.The comparison with the original design scheme is made from the internal force,cross-sectional stress and deflection deformation of the beam body,respectively,to verify that the bridge-forming state after re-tendon matching is more in line with the target characteristics.(5)Using Midas/FEA to perform local stress analysis on the zero block of the prestressed redesigned rigid frame bridge.Introduce the steps of model establishment,boundary condition application,equivalent load simulation,etc,and analyze the stress distribution of No.0 block from the four working conditions of maximum double cantilever in the construction process,maximum negative bending moment and maximum shearing force in the operation stage,so as to judge the rationality of prestress allocation.