Study on refined thermal boundary conditions for bridge temperature field analysis

• Rigorous expressions for bridge thermal boundary conditions are derived. • A novel view factor algorithm enables accurate bridge radiative heat transfer. • Potential errors of simplified boundary conditions are theoretically quantified. • Improper simplified models risk 5°C overestimation in structural temperature. Accurate calculation of bridge temperature fields is of great significance for accurately assessing bridge thermal behavior. However, simplified thermal boundary condition models are widely used in bridge thermal analysis, while their deviations from exact solutions remain unquantified. This study systematically investigates the heat exchange mechanisms between bridges and their environment, develops rigorous expressions for bridge thermal boundary conditions, and evaluates the potential errors introduced by simplified models. Results indicate that accurate calculation of long-wave radiation is the primary challenge in bridge thermal analysis. Although some simplified models yield vertical thermal gradients within acceptable engineering accuracy, inappropriate models may overestimate the overall structural temperature by up to 5°C. These findings are validated through field temperature measurements from a concrete bridge. The potential errors arising from model selection should be given sufficient attention when evaluating bridge thermal effects.