Seismic Analysis Of Curved Bridge With Pounding Effect And Study On The Pounding Mitigation And Unseating Prevention Measures

Bridge is the pivotal project of the transportation network. Because of the good adaptability to restrictions on space and linear, curved continuous girder bridge are widely used in the bridge engineering. Compared with the linear bridge, due to the irregularity of the structure, curve bridge is more likely to suffer damage in the earthquake, which will not only cause huge economic losses, but also make restoration extremely difficult. So the problems of anti-earthquake and disaster prevention of curved bridge has been highly valued by the academia and engineering. Previous experience shows that the action of collision between the adjacent structure and the unseating of bridge is one of the main reasons for structural damage or collapse. Due to the influence of curvature radius, the girder torsion phenomenon of curved bridge is serious, which will be more likely to cause collision between adjacent components. So based on the analysis of the collision response of curved bridges under earthquake and according to the collision characteristics and causes of curved bridges, This thesis makes research on the pounding mitigation and unseating prevention measures. The mainly researches are as follows:(1) Based on the bridge collision theory and compared the simulation method of bridge collision analysis, including the recovery coefficient method, the contact element method, the three-dimensional contact friction element method and the master-slave surface method, the collision response analysis method under earthquake was determined.(2) This thesis putted the commonly used double column pier curved bridges of southwest mountainous area as engineering background, and builted the finite element solid unit model which could consider the uneven 3D contact collision between adjacent components of curved bridges with the master-slave surface method in ABAQUS. The collision response analysis of curved bridge was maked through nonlinear dynamic time history analysis. The results indicated that the crankle coupling phenomenon of curved bridge is serious under earthquake, which caused adjacent structures to be uneven local collision easily, and the collision are generally occur in the side of the structure. The collision area is small, the impact stress is big, which would cause serious damage of reinforced concrete; The collision made the main girder to be great tangential and radial displacement which is easy to cause the happening of dropped beam.(3) Through the comparison of the existing damping device, the pounding mitigation and unseating prevention device, this thesis determined to use viscoelastic damper, viscous dampers, steel wire rope-rubber mat and lead rubber bearing to make seismic control, pounding mitigation and unseating prevention control. The mechanics analysis model of these devices were determined and the bridge structure model was builted which could consider the pounding mitigation and unseating prevention measures.(4) The Influencing factors on the effect of pounding mitigation and unseating prevention were discussed, such as the parametric variation of damping device, pounding mitigation and unseating prevention device. The results indicated that the greater the equivalent stiffness coefficient and the equivalent damping coefficient of the viscoelastic damper, the better the effect of pounding mitigation and unseating prevention; The greater the damping coefficient and the smaller velocity index of viscous dampers, the better the effect; The greater the wire rope stiffness of steel wire rope-rubber mat, the greater the impact force and the smaller the displacement, the greater the thickness of rubber mat, the smaller the impact force and the small change in displacement; The greater the yield strength and stiffness of lead rubber bearing, the better the effect of pounding mitigation and unseating prevention.(5) The pounding mitigation and unseating prevention device were installed inside and outside of the expansion joints or using damping device. Compared and researched the seismic effect of damping device, pounding mitigation and unseating prevention device through nonlinear dynamic time history analysis. The results indicated that the rotation of the girder been resisted by the constraining force or energy dissipation effect of these device; the viscoelastic damper, viscous dampers and lead rubber bearing could reduce well the collision force, number, stress, damage, girder torsion and radial and tangential displacement of the adjacent components of curved bridges. The steel wire rope-rubber mat could be smaller to reduce the collision force, number, stress, damage, girder torsion and radial displacement, and would magnify the collision number, but be the best to ruduce the tangential displacement.(6) The combinatorial optimization of the damping device, pounding mitigation and unseating prevention device were made with the principle of energy dissipation combined with constraints, formed three kinds of combined seismic cases and then maked seismic response analysis. The results indicated that, compared with the case of using damping device, pounding mitigation and unseating prevention device separately, the three kinds of combined seismic cases could be more effective to reduce the collision force, number, stress, damage, girder torsion and displacement, and make the unseating prevention function come true at the same time of shock absorption and pounding mitigation.