Study On Spandrel Structure Design Of Extra Long-span Deck CFST Arch Bridge

Since the first concrete-filled steel tubular(CFST)arch bridge was built in the1990 s,the CFST arch bridge has developed rapidly.According to incomplete statistics,over 400 CFST arch bridges have been built or been constructing,while a span reached530 m.Guangxi Pingnan Third Bridge under construction will be the longest span CFST arch bridge with a span of 575 m.Although most of the CFST arch bridges over 200 m are half-through arch bridges,deck arch bridge is often an ideal bridge type in the mountainous valleys.The structure of reasonable light deck system can reduce the weight of the deck system and the arch ring,affect the spandrel structure and the layout mode,which has become an important factor to affect the further development of the deck arch bridge.At present,the researches on the arch structure of the large-span through-tube CFST arch bridge are relatively rare.Therefor,the studies of the spandrel column and the structure of the deck system are carried out by regarding the Xianghuoyan Bridge as background.(1)Relevant data of CFST arch bridges built and under construction at home and abroad is collected and collated,the structures of the spandrel column and bridge girder from material type and cross-sections is summarized.(2)For the steel-concrete composite beam bridge system,stress features,material usage and operational difficulty of the steel-concrete composite beam with different number of longitudinal girders are analyzed.The advantages and disadvantages of steel box girder,steel box-concrete composite girder,truss-concrete composite girder and steel-concrete composite girder are compared and analyzed,the respective scope of application is obtained.(3)Based on the theory of elastic stability,the influence of the stability problem of high column under boundary conditions is studied,and the relationship between critical force and the cross-section’s structure of column is analyzed by using the formula for stabilization of compressive bar.Combined with the deformation characteristics of the main arch ring under vehicle loads and changed temperature during the service stage,the connection between the deck system and the spandrel column,the influence of the connection on the stability of the high column and stress on the main arch ring are analyzed.(4)The effect of the steel ratio of Xianghuoyan Bridge’ CFST arch ring on the steel pipe and the concrete in pipes is analyzed by using MIDAS/Civil program.The stress of the main arch ring,the stability of high column,the material usage of engineering and wall-thickness of the steel pipe of steel-concrete composite girder and prestressed concrete girder under three different bridge system structures are studied.