Flexural behavior of reinforced concrete beams at low temperatures

This paper performs a comprehensive study on the flexural behavior of reinforced concrete (RC) beams at temperatures ranging from −180 ℃ to 20 ℃. Mechanical properties of steel reinforcements and concrete at low temperatures were first analyzed by tensile tests and uniaxial compressive tests, respectively. Empirical formulae for the mechanical properties of reinforcements and concrete at low temperatures were developed. Subsequently, four-point bending tests were conducted to investigate the bending capacities of RC beams (40 × 40 × 300 mm) at temperatures of 20 ℃, −40 ℃, −80 ℃, −120 ℃, −160 ℃, and −180 ℃. A finite element (FE) model of the RC beams at low temperatures was also established and verified by comparing with the test results. Based on the validated model, a parametric analysis was performed on full-scale RC beams, in consideration with the parameters of reinforcement ratio, compressive strengths of concrete, and the height of a beam. Finally, an analytical model was proposed for the bending capacity of an RC beam at temperatures from −180 ℃ to 20 ℃. Results showed that due to the increased yield strength of reinforcement and compressive strength of concrete, the yield strength and ultimate strength of an RC beam were also obviously increased at low temperatures. As the temperature decreased from 20 ℃ to −40 ℃, −80 ℃, −120 ℃, −160 ℃ and −180 ℃, the ultimate strength of an RC beam was increased by 26.5%, 39.4%, 91.5%, 112.3% and 160.6%, respectively.