Fragility analysis of small- and medium-span bridges under region-specific traffic load characteristics

Overloaded traffic loads can increase the risk of bridge damage and reduce the service life of bridges. To further refine the research on the fragility analysis of different small and medium span bridges to traffic loads by considering the regional characteristics of traffic loads. This article systematically conducts a traffic load fragility analysis of bridges, taking into account the structural characteristics of small- and medium-span bridges and vehicle load characteristics within the region. First, statistical analysis is conducted on the collected measured traffic load data within a certain area, and the Metropolis-Hasting sampling algorithm and Copula function are used to consider the correlation of traffic load parameters to simulate random traffic flow. Then, the calculation method for the resistance level corresponding to the three states of bridge cracking, yielding, and failure is given. Finally, eight types bridges with a high proportion within a certain route is selected, and their fragility to traffic loads has been analyzed. The analysis indicates that the failure probability corresponding to cracking conditions exceeds the serviceability limit state target for all hollow slab bridges, even when the vehicle load limit is set at 15 t. Similarly, T-beam bridges are also relatively easy to enter a state of working with cracks. Furthermore, hollow slab bridges exhibit a higher failure probability than T-beam bridges under identical traffic loading conditions. This indicates that T-beam bridges are more suitable for the current traffic load conditions. In hollow slab bridges, the failure probability of 13m span and 16m is relatively high. In T-beam bridges, the probability of failure is relatively high for 30m span. These bridges should receive more attention in operation and maintenance work. The proposed fragility analysis method for traffic loads can facilitate bridge operation and maintenance, while also guiding the formulation of vehicle load limit policies.