Spatial temperature distribution and fire resistance behavior of double-deck steel truss continuous girder bridges

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Abstract

With the continuous development of transportation infrastructure, vehicle fires occur frequently on bridges and pose a severe threat to the structural safety of bridges. However, the research on temperature field and fire resistance behavior of bridge based on the fire test is still relatively few. This study takes a practical double-deck steel truss continuous girder bridge as the research object, proposes a spatial temperature field simulation method under the action of lower deck fires based on the results of real fire experiments, and explores the distribution laws of the bridge temperature field under different fire-influencing factors. 

On this basis, a thermo-mechanical coupled numerical analysis model is established in combination with the obtained temperature field data to analyze the stress and deformation response characteristics of the bridge under different fire scenarios, thereby revealing the influence mechanism of lower deck fires. The results show that both the fire heat release rate and ambient wind speed exert a significant influence on the post-fire temperature distribution and structural response of the bridge: an increase in the heat release rate raises the maximum deck temperature, while an increase in wind speed expands the high-temperature affected area; under extreme fire conditions, the maximum vertical deformation of the fire-exposed bridge span reaches 416 mm, which far exceeds the specification limits. 

For the double-deck steel truss continuous girder bridge studied in this paper, it is recommended that large trucks and hazardous chemical transport vehicles with a heat release rate of 100 MW and above be prohibited from passing. This study provides a reference for the formulation of vehicle traffic control strategies and the conduct of safety assessment work for double-deck steel truss continuous girder bridges.

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