亚高温持时对混凝土单轴受压力学性能影响研究

Uniaxial compression tests were performed on 144 groups of 100 mm × 100 mm × 300 mm concrete prism specimens to study their mechanical performance after sustained sub-high temperatures. The variations of concrete axial compressive strength，elastic modulus，peak compressive strain，and compressive stress-strain relationship with sustained sub-high temperatures were analyzed. The test results show that when the temperature is constant，the axial compressive strength of concrete degrades with the extension of heating duration，and essentially stabilizes after 24 h of heating. After 24 h at 350 ℃，the concrete axial compressive strength decreases by 21. 2%-44. 7%，the elastic modulus decreases by 63. 6%-75. 6%，and the peak compressive strain increases by 193. 9%-403. 4%. The axial compressive strength of concrete with higher pre-heating strength decreases more significantly after sustained sub-high temperatures. Initial compressive stress mitigates the adverse effects of sustained sub-high temperatures on concrete. Through regression analysis，calculation formulas for the axial compressive strength，elastic modulus，and peak compressive strain were proposed for concrete after sustained sub-high temperatures，and statistical analysis indicates that the average ratios of predicted values to experimental values are 0. 996，1. 004，and 1. 008，respectively. Furthermore，a complete compressive stress-strain curve equation was established for concrete after sustained sub-high temperatures，with an average relative error of 7. 63% between the calculated and experimental results.