Experimental and analytical investigation of the axial load bearing capacity of TRM-confined masonry columns after exposure to elevated temperatures
摘要
This study examines the residual compressive behaviour, failure modes, and mechanical properties of textile-reinforced mortar (TRM)-confined masonry columns following exposure to elevated temperatures. Its main purpose is to investigate the temperature-dependent strength degradation and recovery, and to propose a methodology using existing analytical models (CNR, ACI, RILEM), to assess the residual axial load-bearing capacity. Methods: Two masonry types were tested: a low-strength assemblage representative of heritage structures, confined with a coated carbon fibre grid, and a higher-strength assemblage resembling modern masonry, confined with a dry carbon grid. Specimens were subjected to sustained heating at 100 °C, 200 °C, and 300 °C for 8 h. Tensile and compressive tests were conducted on fibre yarns, TRM coupons, and confined columns. Results: Results revealed a temperature-dependent strength degradation: up to 23% average reduction for low-strength masonry and 13% for high-strength masonry at temperatures below 200 °C. Remarkably, strength recovery was observed at 300 °C, with gains of up to 30% and 8%, respectively. Three existing analytical models were adapted via a proposed methodology to incorporate temperature-dependent degradation laws, yielding preliminary predictions that align with experimental trends. Conclusion: Findings emphasize the complex thermo-mechanical interaction in TRM-confined masonry, especially the strength recovery at 300 °C, and the necessity for further investigation needed to refine existing analytical models to account for the thermal effects.