Impact of longitudinal reinforcement ratio on the flexural performance of RC beams with various sizes at cryogenic temperatures: a two-stage meso-simulation

Abstract

This study presents a three-dimensional mesoscale model to analyze the flexural performance of reinforced concrete (RC) beams at cryogenic temperatures, emphasizing the quantitative effects of temperature, structural size, and longitudinal reinforcement ratio. First, a two-stage mesoscale simulation methodology comprising thermal analysis followed by mechanical analysis was established and validated, incorporating the low-temperature mechanisms that account for ice effect and non-uniform deformations of meso-components. Subsequently, the flexural failures of RC beams with varying sizes (150 × 300, 300 × 600, and 600 × 1200 mm) and longitudinal reinforcement ratios (0.23%, 1.20%, and 2.20%) were performed across a temperature ranging from 20 °C to −90 °C. The cryogenic flexural performance of RC beams was analyzed in terms of concrete damage, steel rebar strain, nominal flexural strengths, and ductility. Numerical results show that the decreasing temperature improves nominal flexural strengths while tend toward brittle failure characteristic. Additionally, the nominal flexural strength at low temperatures displays a slight decrease with the increase of the cross-sectional height, indicating a size effect. The maximum reduction in nominal flexural strengths is about 15% when the cross-sectional height adds from 300 to 1200 mm. Moreover, the decreasing temperature and the increasing longitudinal reinforcement ratio enhance the size effect on nominal flexural strength. Finally, a calculation formula for the ultimate moment of cryogenic RC beams was proposed, which took account of the low-temperature effects. This study offers an efficient methodology for predicting the flexural performance and assessing the ultimate capacity of RC beams at cryogenic temperatures.