Seismic Effect And Mitigation Measures Of Wide Skew Beam Bridge

Wide skew beam bridge is wide used in city bridge. Compared with the orthogonal beam bridge in seismic,wide skew beam bridge can be damaged in higher degree. The main reason is that wide skew beam bridge is not symmetrical layout and the rotation of the special trend in the seismic. There are some failure modes in seismic such as:Failure mode one, the collision damage between girder and abutment back wall,girder and block.Failure mode two, the girders fail due to big displacement and rotation.Failure mode three, the coupling failure of piers due to bending moment, share force and torsion force.Nowadays, there are few researches on seismic mitigation and absorption methods of skew beam bridge. In this paper, we study on seismic shock absorption measures of single span wide skew beam bridge and three spans continuous skew beam bridge in three direction ground motion by using explicit dynamic analysis method of LS-DYNA. This study presents three research results as follow: Result oneTo consider the abutment with filled soil, we choose two special types of ground motion to study the plane rotation effect of single span skew beam bridge with simple supported. The results show three points. Point one, seismic pounding is the back wall and block of the abutment of the constraint on the girder,which we called "colliding constraint",and is the intermittent dynamic constraints inside a bridge. Point two, for simply supported beam bridge there is no regular on direction of main girder rotation in seismic action. Point three, the collision between main girder and abutment is not increasing with ground motions with velocity pulse.Result twoTo study on seismic absorption of continuous wide skew beam bridge, we analysed the dynamic response of bridge structure in two different spectral of ground motion. Our analysis based on the seismic response of girder’s plane rotation, bearing’s yielding, pier’s bottom reactions and so on. For getting more seismic mitigation and absorption of bridge, we used rubber buffer material to the expansion joint between girder, back wall and block. According to the study we got results presenting of three points. Point one, for irregular beam bridge there is no regular on direction of main girder rotation in seismic action, skew beam bridge is no exception.It is the inherent rules of irregular beam bridge under seismic response.The collision will change the rotation degree.Point two, the support on the pier top is easy to yield at the level of constraint in the moderate intensity earthquake.Point three, the rubber buffer material has a significant slowing effect on the beam end collision of the skew beam bridge and effectively reduce the bending-torsional coupling effect of bridge piers.But it also has many shortcomings as the bearings can’t be protect very well and the bending moment of pier bottom can’t be reduced.Result threeBased on rubber buffer material are used in the expansion joint, we studied adding linear viscous dampers or elastic cables to absorb seismic energy of continuous wide skew beam bridge. The results present for two points. Firstly, combining rubber buffer material and elastic cables can effectively prevent the girder falling, significantly reduce the rotation of beam displacement and pier bottom torsion. Secondly, the combination of rubber buffer material and viscous dampers are used in bridge structure can reduce the speed and acceleration of main girder.In addition, it can effectively reduce the main beam and the back wall and the stopper of the impact force, and do some good effects on bending moment and shear of pier bottom in seismic action.It shows the effect of viscous damping damper is ideal, and the bearing failure does not affect the damping effect of viscous dampers.