Based on the 18-month weigh-in-motion (WIM) data of Xuanda Expressway in Hebei Province, the load data of extra-heavy trucks were extracted, the key load parameters including the mass, speed, arrival time and lane distribution of vehicle were investigated, the types of extra-heavy trucks were classified, and the axle load distributions were analyzed. The load cases of 883 extra-heavy trucks were dynamically and visually simulated by using Bridge Dynamics Analysis System, the responses of hollow slab bridges were compared with the design vehicle load effects, and the differences between extra-heavy truck loads and corresponding design loads were investigated. The bearing capacity safety of hollow slab bridges under heavy traffic was investigated by considering the effect combination of dead load and extra-heavy truck load. Analysis result shows that the ratios of extreme values of positive bending moment and shearforce to the corresponding design values are 2.09 and 1.97, respectively, which indicates that the maximum extra-heavy truck loads are obviously higher than vehicle design loads.the ratios of average values of positive bending moment and shear force to the corresponding design values are close to 1.0, which indicates that the average extra-heavy truck load is close to the design vehicle load. The average values of evaluation indexes of bending and shearing bearing capacities fluctuate around 0.50 and 0.40, respectively, the extreme values fluctuate around 0.72 and 0.50, which indicates that the hollow slab bridge at the current design level can satisfy the operation safety requirement under heavy traffic, and the bending capacity has a higher redundancy than the shearing capacity. The evaluation indexes of bearing capacity don't change obviously with the increase of span length, which indicates that the redundancy of bearing capacity remain stable when the span length increases.
