Dynamic Response and Bearing Capacity of Prefabricated Steel Temporary Bridges Under Heavy Crawler Vehicles on Soft Paddy Field Foundations

Many transmission tower foundations in Northeast China are built in paddy fields, requiring construction during the wet season. Currently, no temporary bridge can be quickly installed and removed to transport people, materials, and machines without destroying the fields. To solve this problem, this study designs a prefabricated steel temporary bridge. The dynamic response of the bridge under a 25-ton moving crawler vehicle was studied using both field tests and numerical simulations. This work analyzes how the whole structure and its local parts respond to moving loads on soft paddy soil and calculates its maximum load capacity. The results indicate that: (1) empirical field measurements demonstrate that under the worst condition when the vehicle enters and leaves the bridge (end eccentric loading), the bridge does not lift or overturn; (2) numerical extrapolations indicate that when the 25 t vehicle passes at 1–10 m/s, the dynamic response is stable without resonance, and the dynamic stresses and displacements are always kept within safe limits; (3) the bridge exhibits reliable load capacity and resistance to deformation, with numerical extrapolations indicating that the theoretical ultimate bearing boundary of the system approaches 100 t. However, practical operational loads must incorporate appropriate safety factors and remain significantly below this extreme limit. This system allows heavy equipment to pass quickly and move frequently, while protecting the farmland from damage.