Study On Seismic Design Of Urban Viaduct Limit Device

During earthquake, some lateral shear keys of bridges suffered serious damage that is partly caused by pounding between shear keys and girders. If the shear key is not strong enough to prevent the motion of girders, large displacement of girders will be caused, or even lead to collapse of superstructures, therefore, improve adjacent beam and the pier’s transverse and longitudinal limit device can effectively improve the seismic resistance of bridge, The limit device of urban viaduct is studied in this paper, The collision mechanism between beam and limit device is analyzed, and it has important theoretical significance and value engineering for improving the urban bridge seismic safety. The main research contents and conclusions are as follows:(1) The destroy form of bridge structure in the earthquake is summarized; All of the standard for preventing and falling beam system provided in countries regulate and the research results of the limit device in China are introduced; The fiber model and the plastic hinge restoring force model for reinforced concrete bridge pier are introduced, the basic parameter and Hythesis Character of Takeda trilinear skeleton curve are analyzed; The isolation bearing types and restoring force model are introduced.(2) According to the structure and function mechanism of the shear sliding block, the collision sliding block and elastic-plastic limit block are put forward.(3) The equations of motion of bridge about collision is created by summarizing the existing structure collision research material, the advantages and disadvantages of several major collision models is introduced, the Kelvin model is used,which can simulation impact and collision energy loss in the process, the calculation method of damping coefficient is analyzed. The elastic-plastic collision model that can describe cant sliding block and block type elastic-plastic limit block proposed in this paper is adopted.(4) Taking Nanshan Road Donggang interchange in Lanzhou with engineering background, the finite element model of bridge considering the nonlinear of bearings, limit device’s contact and pier’s elastic-plastic is created by using Midas-civil finite element software. The influence of bridge structure seismic performance decided by limit device’s stiffness, initial clearance and damping is mainly studied. The results shows that:The collision force increased with the contact stiffness’s increase; the collision number between beam and block increased with the initial clearance’s decrease; considering damping will increase the demand of pier’s shear.(5) According to continuous girder bridge having cant sliding block and elastic-plastic limit block, the finite element model of bridge structure considering bearing nonlinear, spacing device and pier elastic-plastic is established, the influence of the change of the limit device yield strength of on the seismic performance is analyzed. Finally, through the comparative study of continuous girder bridge of infinite device, elastic limit device and elastic-plastic limit device. The results show that:yield block can reduce the impact of the upper structure, the yield strength of limit device is suggested taking a20%of the counter force...