Study on solar-induced temperature field and thermal effects of double-layer steel truss girder bridge based on monitoring data

The high thermal conductivity of steel can lead to significantly non-uniform temperature fields in long-span double-layer steel truss girders under solar radiation, thereby inducing unfavorable thermal effects on structural performance and construction control. To investigate the solar-induced temperature field and thermal effects of double-layer steel truss bridges during key construction stages, this study uses an under-construction double-layer steel truss bridge as the case study. A finite element model of the structural temperature field considering shadowing effects was established and validated using field monitoring data. The temperature evolution of the steel truss structure under different meteorological conditions was then analyzed, temperature gradient models for key components were proposed, and the thermal effects during segmental assembly and incremental launching were quantified. The results show that the temperature non-uniformity of steel truss members is significantly stronger under sunny conditions than under rainy conditions. Due to the combined effects of shadowing and deck heat transfer, pronounced temperature gradients develop in key components, including the lower deck, top chords, and web members, and temperature extremes in differently oriented members exhibit evident time lags, revealing a complex spatiotemporal thermal response of the double-layer steel truss bridge under solar radiation. Under typical summer construction conditions, larger daytime temperature differences are more likely to induce deck deformation and reduce segment assembly accuracy; therefore, segment installation is recommended during nighttime or early-morning periods, when temperature differences are relatively smaller and more stable. At the maximum cantilever stage, uniform temperature and temperature gradients affect the structural response differently: temperature gradients have a more pronounced effect on stress response, whereas their influence on lateral displacement is relatively limited.