Design Method and Mechanical Behavior of Modular Composite Steel Temporary Bridges on Soft Paddy Field Foundations

To address the challenges of low bearing capacity in Northeast China’s paddy-field soft foundations and the limitations of summer power line construction, a standardized design method for a novel prefabricated modular steel temporary bridge is proposed. Based on the Winkler elastic foundation beam theory, the operating characteristics of rigid short beams and the subgrade reaction distribution under heavy loads were analyzed. On this basis, combined with in situ static load tests and finite element analysis (FEA), the mechanical performance of the temporary bridge under the static loads of crawler-type and six-wheel construction machinery was investigated. The results indicate that when the bridge deck is subjected to a 25-ton construction vehicle, the maximum stress and displacement in the mid-span condition remain well below the material yield strength and the allowable limits stipulated in the Specifications for Design of Highway Steel Bridges (JTG D64-2015). Furthermore, the temporary bridge structure maintains excellent operational stability under a 100-ton extreme construction load and eccentric loading conditions. This study elucidates the mechanical behavior of the temporary bridge, providing a scientific theoretical basis and engineering reference for the design of temporary transit structures in complex environments such as soft paddy field foundations.