Influence of structural form on hydration-heat-induced temperature rise of precast concrete lining segments for a metro transit station

Abstract

This paper describes research on the effect of structural form on hydration-heat-related changes in large-scale precast concrete lining segments. These segments of mass concrete were used in the construction of an underground metro transit station in Changchun, China, a location where conventional cast-in-place construction is interrupted for months by cold winter weather. Heat of hydration analysis of closed-cavity and solid lining segments was conducted using the finite element method (FEM). Two ambient temperatures of 25°C and 10°C (77°F and 50°F) were selected to simulate segment manufacturing conditions in summer and winter, respectively. The FEM and selected parameters were found to be reasonable because the numerical predictions and experimental observations from the closed-cavity segment were consistent. At both of the ambient temperatures, the maximum internal concrete temperature of the closed-cavity segment was much lower than that in the solid one and the temperature distribution in the closed-cavity segment was more uniform. As a result, thermal stress was lower in the closed-cavity segment than in the solid segment, which reduced the risk for cracking. The closed-cavity form of the lining segments enhanced the structural integrity and durability, and the ability to prefabricate these segments in cold ambient temperatures effectively accelerated construction on this project.