Seismic Detailed Design Of Small And Medium-span Highway Bridge Based On Ductility

Through the investigation of earthquake damage at home and abroad:the lack of the pier shear strength and ductility of column is an important reason causing destruction of column. To ensure that the bridge piers have good ductility and energy dissipation capacity under seismic action, is an important prerequisite for the performance-based seismic design of bridge. The guidelines of our country for seismic design of highway bridges have no specific provisions for the ductility seismic design, especially that considering different performance requirement There is no detailed instructions for the calculating of capacity protected members. Therefore, it is necessary to deepen and refine the ductility seismic design based on the principle of performance design. The research combined with analysis、 theoretical calculation and numerical simulation.The main contents of this paper are as follows:(1) The ductility index and quantitative standards for column is determined. Through the analysis and comparison of domestic and foreign relevant specifications and main research results, preliminary determine the ductility index and quantitative standards. Study on the interrelation between displacement ductility factor, curvature ductility factor and drift ratio. Take the displacement ductility factor as the index of the ductility for the global structure system.(2) Put forward the multiple performance objectives for small and medium-span highway bridges. The multiple performance objectives are as follows:Performance level I-The bridge is in elastic state under E1 earthquake and minor damage under E2 earthquake; Performance level Ⅱ-The bridge is in elastic state under E1 earthquake and repairable damage under E2 earthquake; Performance level Ⅲ-The bridge is in elastic state under E1 earthquake and Serious damage without collapse under E2 earthquake.(3) Put forward suggestions for improving the calculation formula of shear strength of column. The calculation method of the disadvantageous axial force is defined. It is necessary to considing the ductility capacity for the design of shear strength.(4) The main parameters that affect the ductile capacity of RC continuous girder bridge like section form, concrete strength, longitudinal reinforcement and stirrup were quantitative researched, and put forward the design proposals. At the same time, the dynamic axial force affecting the ductility in the lateral direction is also studied.(5) The simplified design method binding the needs and capacity based on ductility is determined. The simplified design method adapts to small and medium-span highway bridges that can be transformed into single degree of freedom.(6) Make clear the idea and implementation method of the design based on multiple performance objectives. Put forward design schemes of hollow slab bridge, the composite girder bridge and other typical bridge to achieve different ductility capacity and performance objectives using pushover method.