Damage and fracture in in-service concrete structures subjected to large diurnal temperature variations based on phase-field approach

Abstract

In-service concrete structures are exposed to the natural environment for extended periods, making them susceptible to performance degradation and cracking due to large diurnal temperature ranges (DTR). This paper presents the development of a novel thermo-mechanical-fatigue coupling phase-field model to investigate the cracking process in in-service concrete structures under varying DTR conditions. The results indicate that concrete walls exposed to different single-day DTRs (20–60 ℃) exhibit phase-field damage without cracking. The phase-field damage is negligible at a 20 ℃ DTR but increases to 0.41 at a 60 ℃ DTR. Considering temperature fatigue, the concrete wall initiates cracking when the DTR exceeds 40 ℃ within 100 cycles. With an increase in DTR from 40 ℃ to 50 ℃ and 60 ℃, the time for crack nucleation decreases from 70 cycles to 29 and 25 cycles, respectively. Concrete walls subjected to 40 ℃ and 50 ℃ DTR exhibit a single crack on the top surface, whereas those exposed to a 60 ℃ DTR have two cracks on the top surface and one crack on each side. Furthermore, the cracks induced by the DTR are surface cracks that exhibit rapid expansion up to a specific length of approximately 140 mm before stabilizing.