Damage of concrete subjected to simultaneous fatigue load and thermal effect

Physical loads and environmental actions have simultaneous effects on concrete in nature. An analytical method is proposed to detect the damage to concrete subjected to four-point flexure fatigue load and thermal hysteresis in freeze–thaw. The interaction of the two kinds of loads on the combined damage, in terms of a coefficient f_D(T), is defined to characterise quantification. Damage is aggravated by the combined loads when f_D(N)>1 as compared to isolated loading. The results show that increasing f_D(N) is always seen in the freezing stage, since damage as a result of tensile stress only is being considered here. Moreover, a critical point above which the damage is aggravated by the combined loads is found by extrapolating the maximum values of f_D(N) until f_D(N)=1 at N = 380 000, that is close to the average life (N = 348 310) obtained from the experiments. This work provides a framework to explore the coupled effects on damage from physical loads and environmental actions.