Analysis Method for the Pouring Stage of Concrete-Filled Steel Tube (CFST) Arch Bridges Considering Time-Varying Heat of Hydration and Elastic Modulus

The behavior of long-span concrete-filled steel tube (CFST) arch bridges during the pouring stage is complex. The coupling effect of the time-varying hydration heat and the evolution of the elastic modulus is crucial for the linear control of the structure. Most of the existing models focus on static self-weight analysis but generally ignore the above-mentioned dynamic heat–force interaction, resulting in significant prediction deviations. In response to this limitation, this paper proposes an analysis method for the injection stage considering the time-varying heat of hydration and elastic modulus of concrete inside the pipe. Firstly, based on the composite index model of the hydration heat and through the reduction of the participating materials, the heat source function of the hydration heat of the arch rib was obtained, and its accuracy was verified by using two test components. Secondly, the equivalent application method of the hydration heat temperature field of the bar system model was proposed. Combined with the modified time-varying model of the elastic modulus at the initial age, the analysis method for the pouring stage of concrete-filled steel tube arch bridges was established. Finally, the accuracy of the proposed method was verified by analysis and calculation combined with engineering examples and comparison with the measured results. The results show that the time-varying heat of hydration and the time-varying elastic modulus during the concrete pouring stage inside the pipe can lead to residual deflection after the arch rib is poured. The calculated value of the example reaches 154 mm, while the influence of the lateral displacement is relatively small and recoverable. The proposed method improves the calculation accuracy by 44.19% compared with the traditional method, which is of great significance for the actual engineering construction control.