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

Abstract

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.