Seismic Performance Evaluation For Curved Continuous Rigid Frame Bridge With Long-span And Tall Piers

Curved continourous rigid frame bridges with long-span and high-pier become main bridge type crossing mountains, plateau gullies and great rivers for its many merits, such as beautiful lines, reasonable structure and mature construction means. Because of its span and pier'hight chanllenging and the obvious bending-torsional coupling effect, the dynamic characteristics are more complex than conventional bridges with low pier and straight beams, its seismic response characteristics are also different from the general bridge. The present "Seismic Design of Highway Engineering" applies only to general bridges whose pier height is less than 30m.The information about the earthquake damage of bridge with tall piers and curved beam is lack and the experience of seismic design is lack now. For above reasons, researching nonlinear seismic response on this type of bridges is very important for design, evaluation and identification.This paper, in the engineering background of a curved continourous rigid frame bridge with long-span and high-pier, establishes the restoring force modle of piers. The longitudinal and transverse section moment-curvature characteristics of piers are solved by spline method. Considering double-elasto-plastic characteristics of piers, a equivalent simulation method on plasticity hinge is put forward. Based on the bending-torsional coupling characteristic, the whole bridge model is established and the double-elasto-plastic seismic response analysis were conducted including the longitudinal direction, the longitudinal with 2/3 times vertical direction, the transverse direction and transverse with 2/3 times vertical direction. Study the forming, development, breakage of the plastic hinge under various cases and analyze its location, orderand number to determine the maximum earthquake which the structure can afford and evaluate the structure seismic performance. The results shows that the maximum earthquake excitation of this structure is transverse excitation at the peak acceleration of 0.6g. Plastic hinge generally appear at the top and bottom position of piers, and is likely to appear at the beam of piers. The plastic damage is easily happen at the bottom position of pier. Engineers should strengthen design and enhance bridges'ductility performance at above position to achieve the purpose of seismic ductility. The results of study in this paper can give reference to the earthquake resistant of the same kind of bridge.