中文摘要：

随着公路交通运输的发展,车辆荷载不断提高,而公路货运中的超限运输情况也非常严重,使得许多旧桥正在承受远远超过其设计荷载等级的重车荷载。过大的车辆荷载致使桥梁结构出现损伤以及承载力退化,严重时甚至引起桥梁垮塌,造成巨大生命财产损失。因此,服役多年并存在显著损伤的既有桥梁的实际承载能力成为研究与工程人员关心的重要问题。本文以位于湖南省省道209线上一座服役43年的钢筋混凝土简支梁桥为试验对象,利用千斤顶加载分别模拟超限运输状态下的单车道与两车道20 t、30 t重车荷载,进行了超限车辆荷载作用下的既有梁桥受力性能的试验研究。研究结果表明：达到挠度允许限值时试验桥梁承受的荷载远大于其设计荷载;在一定程度超限车载作用下结构反应仍呈线性;整个超限车载试验过程中桥梁的横向连接刚度变化很小;两车道3倍30 t重车循环加载时结构出现了明显损伤累积。

英文摘要：

With the development of road transportation,the vehicle load keeps increasing and over-load transportation is becoming more and more serious in highway transportation,which makes many existing highway bridges sustain heavy load much beyond the design.Excessive load would damage the bridge structure,degrade the load-bearing capacity and might even result in collapse.Therefore,the actual load-bearing capacity of those existing bridges with many years of service and significant damages is becoming the concerns of researchers and engineers.In this study,experiments were performed for a simply supported concrete girder bridge on the province road 209 of Hunan province.During the experiments,loads were applied to the bridge through a group of hydraulic jacks to simulate the heavy vehicle loads of 20 ton and 30 ton in single and two-lane,respectively,to study the behavior of existing reinforced concrete bridges under over-limit vehicle load.The experimental results showed that the actual bridge load-bearing capacity was well above its design value even when the structural deflection reached the code limit.Furthermore,the bridge response remained linear to the load level exceeding twice the 30 ton truck loads.On the other hand,there was little variation in the transverse connection stiffness of the bridge during the experiments.However,the accumulated damage of the structure appeared significantly when the cyclic heavy vehicle loads of three times of 30 ton in tow-lane road were applied.