车辆轴限对钢筋混凝土桥梁可靠度和加固费用的影响

为了分析车辆限载对钢筋混凝土桥梁可靠度和加固费用的影响，基于实测车辆动态称重数据和可靠度理论，研究了桥梁可靠度及其年均加固费用与车辆轴限值的关系。首先根据车辆动态称重数据统计得到交通荷载资料，在保持车货运输总重不变的前提下，采用蒙特卡罗法模拟不同轴限值约束下的随机车流。然后，计算桥梁在不同轴限值下的时变可靠度，结合不同加固方案所引起的可靠指标变化确定桥梁剩余使用寿命及其年均加固费用，并拟合确定轴限值与年均加固费用的关系曲线。最后，以湖南某地区的实测车辆动态称重数据及一座典型的钢筋混凝土简支T梁桥为例进行分析说明。研究结果表明：对桥梁进行限载可以减缓桥梁可靠指标的下降速率；在车货运输总重保持不变的条件下，轴限值越大，桥梁的可靠指标下降越快，桥梁使用寿命越短；当轴限值不超过10 t时，桥梁使用寿命可以达到设计使用年限，而当轴限值超过16 t后，桥梁结构的可靠指标随时间下降明显，在达到设计使用年限之前需要采取加固措施；采用3种常见的方案对桥梁进行加固后，桥梁剩余使用寿命随轴限值的增加均呈明显的下降趋势；随着轴限值继续增大，3种加固方案对桥梁剩余使用寿命的影响越来越小，而桥梁年均加固费用却随轴限值的增大呈指数型增长。

Impact of Vehicle Axle Load Limit on Reliability and Strengthening Cost of Reinforced Concrete Bridges

To analyze the impact of vehicle load limit on the reliability and strengthening cost of reinforced concrete bridges, the relationship among the axle load limit, reliability, and annual strengthening cost of the bridge structure was studied, based on the measured weigh-in-motion data and the reliability theory. First, traffic load information was collected based on the weigh-in-motion data. Under the assumption that the total freight weight was constant, random traffic flow was simulated using the Monte-Carlo method under different axle load limits. Then, the time-dependent reliability index of the bridge was calculated for different axle load limits, and the remaining service life of the bridge and the annual strengthening cost were determined by considering the time-dependent reliability after adoption of different strengthening methods. The fitted curve between the axle load limit and annual strengthening cost was obtained accordingly. Finally, the measured weigh-in-motion data of a specific area in the Hunan province and a typical simply-supported T-beam reinforced concrete bridge were considered as examples for the purposes of illustration. The results show that limiting the vehicle load can slow down the reduction of the reliability index of the bridge. Under the assumption of a constant total freight weight, a higher axle load limit can result in a faster reduction of the reliability index and a shorter service life of the bridge. When the axle load limit is no greater than 10 t, the bridge service life can satisfy the design service life. However, if the axle load limit is higher than 16 t, the reliability index of the bridge demonstrates significant reduction, and the bridge structure is required to be strengthened to satisfy the design service life. After the bridge is strengthened using three types of common strengthening methods, the remaining service life of the bridge shows a clear downward trend with the increase in the axle load limit. More specifically, if the axle load limit continues to increase, the difference between the remaining service life using different strengthening methods becomes smaller, while the annual strengthening cost is found to increase exponentially with the increase of the axle load limit.