兰州西固黄河大桥横向抗震体系研究

摘要

The main bridge of the Xigu Huanghe River Bridge in Lanzhou is a steel and concrete composite girder cable-stayed bridge with double pylons,double cable planes and with span arrangement (67+110+360+110+67) m.The approach bridge of the bridge on the south bank is the prestressed concrete simply-supported box girder bridge with spans of 2 × 40 m while that on the north bank is the prestressed concrete continuous box girder bridge with spans of 5 × 40 m.To determine the reasonable transverse seismic system for the bridge and optimize the arrangement of the seismic system,the program SAP2000 Nonlinear was used to establish the finite element model for the whole bridge of the bridge,the seismic responses of the bridge under the 4 types of the pier-main girder transverse constraint systems,such as the transverse sliding system,transition pier constraint system,auxiliary pier constraint system and the transverse complete constraint system,were analyzed and with regard to the seismic reducing measures of the transverse retainers,the influences of the control parameters of the retainers using the different materials on the seismic performance were analyzed as well.The results yield that the seismic responses of the piers under the transverse sliding system are the least,but the transverse relative displacement of the piermain girder is great.The transverse constraint systems of the transition and auxiliary piers may increase the seismic responses of the corresponding piers,of which the increase of the seismic responses from the constraint system of the auxiliary pier will be more significant.Under the transverse complete constraint system,the forces generated in the different piers are unfavorable.The rigid concrete retainers are difficult to reduce the seismic responses of the transition and auxiliary piers at the same time and the transverse seismic reducing effect is not good.The application of the elastoplastic retainers can significantly decrease the internal forces in the transition and auxiliary pier footings and the transverse relative displacement of the pier-main girder.%兰州西固黄河大桥主桥为(67+110+360+110+67)m双塔双索面钢—混结合梁斜拉桥,南岸引桥为2×40 m预应力混凝土简支箱梁桥,北岸引桥为5×40 m预应力混凝土连续箱梁桥.为确定该桥的合理横向抗震体系并优化其布置形式,采用SAP2000 Nonlinear程序建立全桥有限元模型,分析该桥在横向滑动、过渡墩约束、辅助墩约束及横向完全约束4种墩梁横向约束体系下的地震响应,并针对横向挡块减震措施分析不同材料挡块控制参数对抗震性能的影响.结果表明:横向滑动体系下桥墩的地震响应最小,但墩—梁横向相对位移较大;过渡墩横向约束和辅助墩横向约束体系均会增大相应桥墩的地震响应,其中辅助墩横向约束体系下增加更为明显;横向完全约束体系下,各墩受力均不利;混凝土刚性挡块难以同时减小过渡墩与辅助墩的地震响应,横向减震效果不好;采用弹塑性挡块能显著降低过渡墩与辅助墩的墩底内力和墩—梁横向相对位移.