Review on thermal behavior of concrete-filled steel tube bridges under environmental effects

Key temperature issues faced by concrete-filled steel tube (CFST) bridges under the influence of hydration heat and environmental factors were compiled to enhance their capacity in addressing temperature response. Research advances in temperature actions and effects during construction and operation, interfacial thermal debonding, and computational methods for temperature effects were reviewed, and future research directions were discussed. Research findings indicate that the assembly of empty steel tubes is significantly influenced by the solar temperature field during the construction stage, and thus assembly demands precise alignment control. The hydration heat of concrete in the tubes results in that the temperature rise at large-diameter (> 1.2 m) sections and the core-surface temperature differences are over 30 ℃, raising concrete cracking risks. There is controversy regarding the selection of the closure temperature for CFST arches. It requires back-calculation with cumulative internal force. In operation, air temperature variations induce uniform temperature changes, while solar radiation creates nonlinear temperature gradients (temperature difference > 10 ℃) at sections. Temperature effects significantly impact stress, internal force, deformation, and stability and alter the long-term response of the structure by accelerating concrete creep. The temperature difference between the steel tube and core concrete can easily induce excessive tensile stress at the steel-concrete interface and thermal debonding, with the debonding height ranging from approximately 0.03 to 0.72 mm. Interface debonding can be effectively detected via infrared thermography, distributed fiber optic sensing, and other temperature sensing technologies. Current codes lack precise definitions for temperature action patterns and linear expansion coefficients. Analytical methods (such as thermoelastic analysis and energy method) and refined thermo-mechanical coupling simulation provides support for calculations of temperature effects. Future priorities include developing materials with low hydration heat and radiation absorptivity, promoting the application of interface connectors, implementing long-term thermal damage evolution and assessment, optimizing temperature control strategies for super-long-span CFST bridges, and refining relevant design codes. The research results offer a theoretical reference for the high-quality construction and long-life operation and maintenance of CFST bridges.