不同约束体系对双层曲线梁桥地震响应的影响

Influence of Different Constraint Systems on Seismic Response of Double-layer Curved Girder Bridge

双层曲线梁桥可以在较短距离内实现较大的爬高,由于特殊的结构形式使其地震响应有别于规则桥梁,而支座和限位装置组成的约束体系是影响桥梁结构地震响应的关键。为得到双层曲线梁桥的合理约束体系,基于一座双层曲线梁桥建立有限元模型,进行地震作用下的动力分析,对比球型钢支座、板式橡胶支座和盆式支座的位移和桥墩截面曲率,并将剪力销作为双层曲线梁桥的限位装置,研究剪力销与不同支座组成的约束体系对双层曲线梁桥结构地震响应的影响。结果表明:在地震作用下,双层曲线梁桥的上层支座位移普遍大于下层,双层约束体系使得桥墩中部的截面曲率和延性要比墩顶和墩底的小;球型钢支座的支座位移较小,传递到桥墩的地震力较大,设置剪力销后支座位移减小,桥墩损伤未发生明显变化;板式橡胶支座的支座位移较大,在地震动强度较小时就发生滑动,支座滑移可耗散能量使桥墩的损伤程度降低,但与剪力销组合后支座位移受到限制,传递到桥墩的地震力成倍增加,桥墩损伤最为严重;盆式支座的支座位移较小且上下层位移值最为接近,传递到桥墩的地震力较为均匀,在一定程度上保护了桥墩,考虑剪力销后,支座变形减小到允许范围之内,桥墩损伤略有增加。因此,本研究认为盆式支座与剪力销的组合是该双层曲线梁桥的合理约束体系。

Double-layer curved girder bridge can achieve a large climb in a short distance, and its seismic response is different from regular bridge due to its special structural form. The constraint system consisting of bearings and limiters is the key to affect the seismic response of bridge structure. To obtain the reasonable constraint system of double-layer curved girder bridge, a FE model of a double-layer curved girder bridge is established for dynamic analysis under seismic action. The displacements of spherical steel bearings, elastomeric pad bearings and pot bearings and the curvatures of pier sections are compared. Regarding the shear as the limiter of the bridge, the influences of the constraint system consisting of shear pins and different bearings on the seismic response of the double-layer curved girder bridge structure are studied. The result shows that(1) Under seismic action, the displacement of the upper bearings of the double-layer curved girder bridge is generally larger than that of the lower layer, the double-layer constraint system makes the section curvature and ductility in the middle of the pier smaller than those of the pier top and bottom.(2)The displacement of spherical steel bearings is smaller, while the seismic force transmitted to the pier is larger. After setting the shear pins, the bearing displacement decreased, and the damage of bridge piers has not changed obviously.(3) The displacement of elastomeric pad bearings is going up, sliding will occur within the smaller ground motion intensity and reduce the damage degree of the bridge piers. Moreover, the application of shear pins limits the displacement of the bearings, which leads to a multiple increase of the seismic force transmitting to the piers to cause the most serious pier damage.(4) The displacement of pot bearings is relatively smaller and the displacements of the upper and lower layers are the closest. The seismic inertial force transmitting to the piers is relatively uniform, which can protect the piers to a certain extent. After considering the shear pins, the deformation is within the allowable range, and the damage of the piers increased slightly. Therefore, it is concluded that the combination of pot bearings and shear pins is a reasonable constraint system of the double-layer curved girder bridge.