Seismic Response Analysis Of Skew Highway Box-Girder Briges

With the rapid development of science and technology, modern bridge designing notion and thought are undergoing tremendous changes. Skew bridge is more and more widely used because of its smooth lines and distinctive outer structure. In fact, the skew bridge can not only adapt to terrain and environmental constraints better, but in some cases can shorten the length of the bridge, thus saving materials and investment compared with orthogonal bridge.This paper begins with the typical phenomena of highway skew bridge damaged in the earthquake, damage mechanism and seismic response parameter analysis, and then introduces briefly the basic formula and calculating methods of both response spectrum and time history analysis method, finally employs finite element software constructing a finite element model of the skew bridge to analyze seismic response parameters systematically and it reaches the following conclusions:(1) As to single-span simply-supported skew bridge, the direction of seismic ground motion has a great influence on shearing force, which changes with the skew angles, no matter which method is employed, either response spectrum method or time history analysis method. When the response spectrum method is adopted and the input ground motion is along the NT direction, the combination of seismic ground motion is one of the factors.(2) If the block is considered, its horizontal thrust at an obtuse angle is greater than at the acute angle, and the thrust decreases as the skew angle increases.(3) Compared with the orthogonal bridge, skew bridge has the coupling characteristics in space, that is to say, when internal forces in one direction is generated, it will also be produced in the orthogonal direction, which is accompanied by the generation of torque. If seismic ground motion input along the X and Y, N direction, the bending moment of pier, the coupling degree of shearing force and the torque of pier increase as the skew angle increases; if the motion inputs along the T direction, they will not generate torque, no matter how steep the angle, which is because the T direction is the direction of bearing support line of skew bridge basis, the torsional coupling will not happen in this direction.(4) As for continuous skew bridges, suppose the skew angle is fixed, the shearing force of pier base does not change obviously with the increasing of pier highness, since it is directly related to the shear stiffness. When the pier is short, the stiffness is higher and the shearing force is bigger; as the pier increases, the stiffness becomes relatively small, but if the structural response is large, shearing force may also be great; the torque of pier base increase with the increasing of the height, forming a linear relationship.(5) It can reduce the internal force effectively when the nonlinear of bearing and the pier is taken into consideration, because their hysteretic behaviors consume considerable energy.