Stress-Strain Properties of Concrete Under Elevated Temperature

This thesis focuses on the compressive stress-strain behavior of unreinforced North American concrete under elevated temperatures from fire. A database on the temperature-dependent properties of concrete is developed from previous experimental research. Predictive multiple least squares regression relationships are proposed for the concrete strength, elastic modulus, strain at peak stress, ultimate strain, and stress-strain behavior, including the temperature, aggregate type, test type, and strength at room temperature as parameters. High-strength and normal-strength, and normal-weight and light-weight materials are considered. It is shown that at elevated temperatures, the concrete strength and elastic modulus are significantly reduced, whereas the strain at peak stress and ultimate strain are increased. Differences between high-strength and normal-strength concrete are quantified. In comparison with previous temperature-dependent relationships, the proposed relationships utilize a larger dataset. Furthermore, the previous models implicitly include creep strains, whereas the proposed relationships provide a baseline to which creep strains could be explicitly added.