桥头引道沉降对简支梁冲击效应的影响分析

Impact influence of a bridge approach differential settlement on a simply supported bridge

针对旧桥中经常出现的桥头引道及伸缩缝破损情况,考虑接缝处沉降差引起的桥头跳车对桥梁振动的影响,提出与错台高度相关的桥头衔接状况五个等级划分标准。以我国常见的中小跨径简支梁为对象,基于五参数车辆模型的车桥耦合系统运动方程,用Newmark法进行数值求解,分析桥头引道沉降差对桥梁振动的影响。研究表明随着沉降差增加,汽车对桥梁的冲击效应明显变大,且随着车速的增大,冲击效应变大。沉降差在桥梁中产生的动力放大系数随着跨径增大而减小。另外,桥头沉降差使车辆竖向加速度瞬时变大,其绝对值随着错台高度的增加而迅速增大,该加速度变化与桥梁跨径无关。

The bridge approach and expansion joint are often damaged in old bridges.The effect of a vehicle bumping caused by a bridge approach differential settlement at the joint on the bridge vibration was studied.The approach state was divided into five grades according to the settlement at abutments.Based on a five-parameter vehicle-bridge coupled model,its vibration equation was deduced and Newmark method was used to solve the equation.Taking a short span simply supported beam bridge as an object,the influence of approach fault on the bridge vibration was analyzed.It was found that the settlement of an abutment affected the bridge vibration and with increase in the settlement the impact of the vehicle to the bridge increased obviously.The dynamic amplification factor caused by the settlement was much bigger in a short span beam than that in a long span one.With increase in the vehicle speed,the impact effect increased and the influence region also expanded.In addition,the settlement at abutments caused increase in the vehicle acceleration which was not affected by the span of a bridge.