Thermal performance of damaged bulk grain warehouse walls under cyclic loading

The walls of bulk grain flat warehouses were found to be prone to cumulative damage under long-term cyclic grain loading, leading to degradation of thermal insulation performance and compromised grain storage functionality. To investigate the damage evolution of brick walls and its thermal effects, cyclic loading tests with 6 cycles at 0.3, 0.5, and 0.7 times the cracking load and post-damage thermal performance tests were conducted. Experimental results indicated wall displacement progressively increased with loading levels and cycle numbers, reaching a maximum deflection of 18.58 mm, with residual deformations ranging from 0.1 to 0.4 mm per cycle. The damage coefficient increases with both the loading level and the number of cycles. Within the loading level range of 0.3 to 0.7 times, the rate of increase in the damage coefficient exhibits a trend of initial growth followed by a gradual decrease. Within the 0.3 to 0.5 times loading range, the wall entered a phase of accelerated damage development, whereas from 0.5 to 0.7 times, damage progression stabilized. The extent of brick wall damage directly governs thermal performance, with greater damage yielding both reduced thermal resistance and an increased heat transfer coefficient. The mid-height section of the wall consistently exhibited the most severe damage across all loading levels. When subjected to loads ranging from 0.3 to 0.7 times the cracking load, the damage coefficient increased from 0.26 to 0.44, accompanied by a 27.45% reduction in thermal resistance and a 26.97% increase in the heat transfer coefficient. Combining mechanical damage test results across varying loading magnitudes and cycle counts with thermal performance characterization data, two quantitative relationship models between the damage coefficient of brick walls and loading parameter and the heat transfer coefficient of damaged brick walls and the damage coefficient were obtained through fitting.