简支与连续梁桥在汽车制动作用下的冲击系数对比研究

Study of Impact Factors of Simply-Supported and Continuous Concrete Girder Bridges due to Vehicle Braking

为了比较汽车制动时简支梁桥与连续梁桥的动力冲击系数(IM),分别选取了跨径为30 m和70 m的混凝土T梁桥和箱梁桥各2座,基于车桥耦合振动模型,计算了该4座不同截面和跨径的混凝土梁桥在一辆三轴车不同工况下匀速与制动作用时的冲击系数。研究工况包括:3种减速度(a)、6个不同初速度(v)、7个不同的刹车位置(P)、3种不同等级的路面不平整度水平(RSC),并将计算的冲击系数与我国现行规范进行了对比。结果表明:其他条件相同时,车辆在连续梁桥不同跨内刹车时产生的冲击系数的变化规律不一定相同,有必要分跨分别考虑;路面粗糙度增大,车辆制动时对桥梁动力的影响增大;汽车制动会显著影响桥梁的动力响应,IM的数值与减速度绝对值基本呈递增的关系。

In order to compare the dynamic impact factors(IM)of simply-supported girder bridges and continuous girder bridges under vehicle braking,two concrete T-beam bridges and Box girder bridges with spans of 30 m and 70 m respectively were selected in this paper.The impact factors of the concrete bridges with different cross sections and spans under different braking conditions of a three axle vehicle were obtained based on a vehicle-bridge coupled model.The study conditions include:3 deceleration rates(a),6 different initial vehicle speeds(v),7 different brake positions(P),3 different levels of road roughness condition(RSC).A comparison was also made between the calculated IM and those specified in the current Chinese bridge design code.The results show that,when other conditions being the same,the change law of the impact factors produced by vehicle braking in different span of continuous girder bridge is not necessarily the same,so it is necessary to consider the span separately.Vehicle braking has a significant effect on the bridge impact factors,and the impact factors increase with the absolute value of deceleration rate.