Study on temperature effect of double-layer steel truss suspension bridge in mountainous area based on environmental parameter field measurement

The temperature field distribution of long-span bridges in mountainous areas is highly complex due to site conditions and shading effects. Thus, to accurate evaluation of these temperature effects, this study presents a FEM-based thermal analysis framework of bridge based on environmental parameter measurements to address this challenge. Firstly, taking a typical double-layer steel truss suspension bridge (DLSTSB) in mountainous area as an example, the distribution law of environmental parameters was analyzed, and its daily variation model was established. Then, 2D finite element models of the bridge tower and main girder were developed in ANSYS to derive temperature gradient models, and a global bridge finite element model via MIDAS/CIVIL was then constructed to evaluate the structural responses under non-uniform temperature loads. The results show that the gradient changes of the bridge tower are concentrated within a 0.7 m wall thickness, and there is a significant temperature hysteresis under the high temperature condition. The temperature gradient in the upper deck is linear and confined to the asphalt pavement layer, whereas the lower deck experiences higher temperature variations under non-obstruction than obstruction. Lateral non-uniform temperatures significantly influence bridge deck displacements, with maximum lateral displacement differences of 19.8 mm for the upper chord and 15 mm for the lower chord. The proposed framework and findings provide valuable insights for analyzing the temperature effects of similar bridge structures.