Study on temperature distribution characteristics of steel-shell concrete tower in double-deck steel truss suspension bridge under tanker fire

Steel-shell concrete bridge towers are widely used in long-span bridges due to their excellent mechanical performance and construction efficiency. However, studies on their temperature distribution and heat transfer behavior under extreme fire conditions remain limited. This paper investigates the thermal response characteristics of a steel-shell concrete tower on a double-deck truss-stiffened suspension bridge using a coupled Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) approach, considering tanker fire scenarios on both upper and lower decks. The results indicate that wind speed significantly affects flame shape and wall temperature distribution, with the area of high-temperature zones and peak air temperatures initially increasing and then decreasing as wind speed rises. The longitudinal position of the fire source along the bridge also has a notable impact on thermal effects. A comprehensive evaluation method is proposed, incorporating wall air temperature and high-temperature zone area, to identify the most unfavorable fire scenarios. The findings show that upper-deck fires pose a greater risk to the tower than lower-deck fires. Under the most severe upper-deck fire condition, the maximum temperature of the steel shell reaches 972 °C, while the peak temperature of the concrete is around 650 °C, decreasing approximately linearly with depth to below 50 °C at 200 mm. The steel shell and ribs exhibit rapid heat transfer, forming distinct temperature gradients, while the internal concrete shows delayed temperature rise, demonstrating good thermal inertia. These findings clearly reveal the heat transfer characteristics of steel-shell concrete towers under fire exposure and provide valuable reference for fire-resistant design and safety assessment of similar structures.