The Study Of Mechanical Properties Of High-pier Large-span Continuous Rigid Frame Bridge

With the vigorous development of western mountainous area transportation infrastructure, long-span continuous rigid frame bridge with high piers has been widely used and developed. Pier height and main span tend to be increasing, the stability problems and dynamic analysis is necessary. In addition, there have been many problems in the application of continuous rigid frame bridge, such as creep deflection and cracking, Therefore, the researches of high pier on the basic mechanical properties of long span continuous rigid frame appears very necessary, In this paper, combined with a large span high pier continuous rigid frame bridge Qian Jiang bridge in the highway of Guang Xi Gui Ping to Lai Bin, some mechanical problems of the continuous rigid frame bridge are studied, the following work was completed:(1) A comprehensive review for the origin, development and structure mechanical characteristics of long span continuous rigid frame bridge is made.(2) The plan comparation for the form of Qian Jiang bridge is consulted and the design of Qian Jiang Bridge is finished based on the detailed design of Qian Jiang Bridge, which is including upper and lower structure, construction process.(3)The three-dimensional finite element model of Qian Jiang bridge is built by bridge finite analysis software, various actions are considered, the whole process of bridge construction are analyzed in detail, focusing on the internal force analysis of three typical construction stages, internal force calculation and structural safety check is made for the durable bearing capacity limit state condition, Serviceability limit state and brief status, the result indicates that the design of the structure meets the specification requirements. At the same time, the dynamic characteristics analysis of the structure is carried on, verifying the correctness of structure analysis model further.(4)The influence of bridge pier stiffness on the of main girder internal force distribution is studied, the main girder internal force is considered based on three different pier cross-section sizes and three different kinds of main pier heights. The main girder internal force condition tends to be the stress condition of fixed end beam when the bridge pier rigidity increases. The girder internal force condition tends to be the stress condition of continuous beam when the bridge pier rigidity is small.(5)The structure stability of Qian Jiang Bridge is studied and the buckling stability is analyzed based on three typical construction stages(pier construction is finished, maximum cantilever stage, the whole bridge construction is finished). The first order buckling mode of the three typical construction phases is characterized by longitudinal instability of structure, the stable coefficient of the maximum cantilever state in construction process is relatively small, but it meets the specification requirements. The stability of the maximum cantilever state and bridge construction finished stage are analyzed through the main pier stiffness changes, the results indicates that increasing of cross section width or high pier is beneficial to enhance the structural stability, on the other hand, the structure buckling coefficient decreased, these features have good guidance meaning for the arrangement of bridge spans, the size of the proposed bridge pier and the guide for construction control.