High temperatures are considered one of the causes of damage to reinforced concrete structures, which placing the concrete in such conditions accompanied by reducing the mechanical properties of concrete. The simultaneous effect of both factors on the reinforced concrete structures is examined. For this aim, several concrete samples were made, and they were exposed to temperatures of 28, 100, 150, 200, 250, 250, 300, 400, 600, 700, and 800 °C. The samples were immediately exposed to compressive and loading steps. The modulus of elasticity and fracture energy of the samples were compared at different temperatures to examine the results more accurately. It was found that as the test temperature increases, the amount of compressive stress of concrete decreases, and the corresponding stress strains have an upward trend in maximum monotonic and cyclic loads, accordingly. Comparing the vertical strain and transverse strain at 800 °C with ambient temperature indicated an increase of 84% and 122%, respectively.
It was found that as the test temperature increases, the elasticity modulus in all loading steps decreases, which the significant damage to concrete is at temperatures above 500 °C. Besides, as the load cycles increase from 1 to 22, the elasticity modulus is almost constant, and no significant changes were observed. In the loading mode, the energy change process is similar to that of the load energy, and as the test temperature and loading steps increase, the number of energy increases.
