Research On Structural Design Parameters And Three Dimensional Mechanical Properties Of Long-Span Curved Extradosed Bridge

Extradosed bridge is a new type of composite bridge between continuous beam bridge and cable-stayed bridge,including superiorities of both combined and being cost-effiective.In recent years,the structural features and mechanical properties of extradosed bridges are studied detailly by many expertise and scholars.However,research on structural design and mechanical property of long-span,multiple cable plane,curved and wide extradosed bridge is rare.Hence,it is necessary to do research on this kind of bridge in order to comsumate design theory of extradosed bridge.In this thesis,based on Huanglongdai curved extradosed bridge,the structural design parameters and spatial mechanical properties of curved and wide extradosed bridge are well studied,which can provide reference for future bridge design and construction of the same type.Main works are as follows:(1)The research achievements of extradosed bridges around the world are collected.Then,the reasonable structural forms and parameters are summarized by doing regression analysis to main structural design parameters of curved extradosed bridges,such as structural system,ratio of side to main span,height of main tower,radius of curve and so on.(2)Finite element models are set up based on different structural systems and design parameters,utilizing MIDAS/Civil finite element software.The influence of different design parameters selection on mechanical properties of Huanglongdai Bridge is analyzed in order to optimize design and choose right structure type and parameters.(3)The whole finite element model of Huanglongdai Bridge is built based on spaitial beam finite element software-TDV RM,in order to comprehensively analyze its performance in construction,completion and operation periods,complying with exisiting design codes.At the same time,aiming at verifying security and rationality of this design,the sensitivities to design parameters of this long-span curved and wide extradosed bridge are detailly studied.(4)By comparison between solid and beam model,the heterogeneity and peak value of the stress in the section of the girder are researched,providing reference for the control and slection creteria of stress in the girder.In the meantime,the distribution of shear stress in this wide box girder with three webs in Huanglongdai Extradosed Bridge are studied,as well as the distribution of normal stress in the bottom slab.(5)Using spaitial solid finite element software-MIDAS/Fea,the detail model of anchorage zone of the cable and the girder is built,in order to analyze the distribution of local stress and verify the security of the structural design of this anchorage zone.The transmission and distribution of vertical force in the cables located at the end of the long cantilever flange is analyzed to provide reference for the anchorage design of the cables at the end of long cantilever flanges.