Model Test And Fatigue Stiffness Study Of PPC Cable-stayed Bridge

Prestressed concrete(PC)cable-stayed bridge has become an necessary part of long-span bridges.The main girder of PC cable-stayed bridge usually designed with full PC part in the early age.With the limitation of full prestressed design in PC cable-stayed bridges and the related problems exposed continuously,design of partial prestressed concrete(PPC)has gradually entered the designation of concrete cable-stayed bridge.How to verify the feasibility of PPC design in the design of concrete cable-stayed bridge is the process that must be experienced in popularizing and applying for PPC cable-stayed bridge.The main work of the paper is as follows,1、Consulting relevant data and summarize the history and the development of concrete cable-stayed bridge and partial prestressed concrete(PPC)bridge,and the fatigue problems and current research status of partial prestressed bridge.2、The fatigue damage model and fatigue damage accumulation theory of concrete beams based on fracture mechanics are introduced in detail.Summarizing the fatigue damage model of every component of concrete beam,and the damage representation method based on deflection is derived.It provides a theoretical basis for further research,analysis and calculation3、We has built an scale model of the main span for 220m cable-stayed bridge,the main beam of the model designed in type B PPC part.Static load and fatigue tests were carried out according to relevant codes used to simulate the whole fatigue process in real bridges.The law of structural response under lane load and fatigue stiffness degradation under different initial damage has been acquired based on parameters of deflection,cable force and crack of main beam in test.The results show that the main beam before and after cracking,the net section stiffness of surface concrete decreases greatly,but the structure stiffness degradation is relatively little.Fatigue won’t cause structural stiffness degradation when the main beam without damage.Fatigue damage to structural stiffness is limited.Based on the above conclusions,the fatigue resistance of the PPC designed concrete cable-stayed bridge is preliminarily verified.4、Analyzed the basic data obtained in the test and selected the relevant calculation model.Construct the structural reference stiffness model,identify the variation of boundary conditions under different working conditions,and establish a unified whole structure stiffness correction model based on the actual crack measurement data.The results show that the stiffness decline of the structure is limited,the rate of fatigue stiffness degradation is related to the initial damage,and the stiffness calculated based on the written data is conservative.The fatigue resistance of the structure is superior.