Seismic Response Analysis Of Rigid Frame-continuous Composite Girder Bridge

Continuous bridges are advanced in better mechanical performance and perfect technique, but need rubber bearings with large tonnage, and large amount of maintenance work. The fixed pier of continuous rigid-frame bridges improves the mechanical performance of structure under horizontal load( such as the action of earthquake). This structure has better crossover capability, but its serviceable range is limited because of the complex stress of fixed pier. Rigid frame-continuous composite girder bridges have the advantage of both styles and overcome their disadvantage. They are particularly good in mechanical characteristics, using functions and environment adaptability, because the demand of the height of fixed pier is reduced compared to that of long unit and long span continuous rigid-frame bridges.Modern economy depends on the traffic line more and more. Once bridges - the key projects of traffic line- were ruined in earthquake, it would lead to great losses of life and property. Therefore, Seismic Response Analysis and necessary preventive measure must be taken to protecting the bridges of great importance. The calculations of rigid frame - continuous composite system girder bridges are not defined clearly in existing seismic code. Based on relevant guidelines about seismic design in the new guidelines for seismic design, an analysis of seismic elasticity and ductility response about the Beiyilu Bridge was taken in this paper to provide basis and reference to this project, and improve theoretical and practical experience for the seismic design of later projects.Several main parts are included in this paper:With the study of Beiyilu Bridge in Urumchi, N-M-φrelationship about the plastic hinge section of this bridge was programmed, Moment- curvature curve was calculated and drawn, and then transformed into equivalent Double Broken Line Model according to the guidelines. According to the structure characteristics of the Beiyilu bridge, the modeling with and without cables is performed by ANSYS to analyze the dynamic behavior of the bridge. The seismic response under the design response spectrum and 3 typical seismic waves is analyzed by response spectrum method and time-history analysis method. The seismic behavior of the bridge is analyzed completely to provide the theoretical reference for the bridge construction and design.Thirdly, the finite element model for the whole bridge with cables was established, with the Multipoint Constraint Element (MCP184) and the Combination Element (COMBIN40) used for simulating the rigid arm and spring connections respectively so as to consider the non-linearity of material in the plastic hinge that may occur in the real structure. The seismic response behavior of the bridge under uniform excitation characterized by Taft earthquake wave was analyzed by the time-history method, from which the longitudinal and transverse bending capacity of Rigid frame-Continuous Composite Girder Bridge under earthquake was quantitatively identified. The comparison of the non-linear analysis above and the traditional elastic analysis was made on the basis of their results, which offered some beneficial conclusions about the analysis and design of bridges of the same kind.