Research on the Temperature Field and Bridge Alignment Influence of Long-span High and Low Tower Track Cable-stayed Bridges under Solar Radiation

To explore the influence of temperature on the alignment of a high-span, high-tower special railway bridge by examining the temperature distribution of the bridge towers and the corresponding positional changes of the high and low towers. Deformation data from the Chongqing Nanjimen rail special bridge during the winter and summer of 2024 were analyzed. The results indicate that the temperature fluctuation of the low tower is significantly greater than that of the high tower, showing higher sensitivity to temperature variations. The maximum lateral temperature gradients of the two towers occurred at 15:00 at the crossbeam, reaching 17.9°C and 21.9°C, respectively. Under thermal effects, the deformation of the low tower was considerably larger than that of the high tower. During the cooling stage, the top deformation and maximum longitudinal deformation of the low tower reached 73.3 mm and −141.7 mm, respectively. Under extreme winter and summer conditions, the low tower exhibited larger longitudinal deformation, whereas the high tower showed more pronounced lateral and vertical deformations. Recommendations: enhance vertical/lateral stiffness and temperature control for the high tower; focus on longitudinal deformation, material selection, and monitoring for the low tower to ensure long‑term stability.