Simulation Analysis of Thermal Stress of CFST Arch Bridge During Exothermic Hydration Process

Abstract

In recent decades, concrete-filled steel tube (CFST) arch bridges have been widely constructed in China. With the increasing span and arch rib diameter of CFST arch bridges, the hydration heat of pumped mass concrete in the CFST arch causes greater temperature changes during the period of construction, leading to potential thermal stress-induced cracking of mass concrete enclosed in the steel tube. In this paper, a finite element model was established to simulate the hydration heat transfer process of large-meter CFST arch which was compared with the measured data from the literature. Subsequently, the variation of thermal stress during hardening process was revealed combining with numerical implementation and analytical study, and there is a reasonable agreement between the analytical solutions and those obtained by numerical implementation. In addition, the effect of concrete creep on the thermal stresses due to hydration heat was taking into account in the calculation based on the relaxation coefficient method. The results show that the nonlinear temperature field generated from the hydration heat determines the nonlinear variation of the thermal stress of CFST structure during hardening process. The thermal stress increases rapidly at the beginning of the concrete hydration, and there is a large stress gradient along the radial direction of the arch cross section; the stress slowly decreases after peak, and there is residual thermal tensile stress in the concrete after the heat release. Concrete creep significantly reduces the thermal stress of the concrete in the early age, but the effect on the thermal stress of the steel tube is negligible.