Compressive behavior of square CFSST stub columns under freeze-thaw cycles

This study systematically evaluates the effects of freeze-thaw cycles on the compressive performance of square concrete-filled stainless-steel tubular (CFSST) stub columns through rapid freeze-thaw tests. This research was performed with 39 sets of test specimens, systematically examining the critical parameters of freeze-thaw cycles (0 to 100 cycles), steel tube wall thickness (1.0 to 1.5 mm), and core concrete compressive strength (20 to 40 MPa). The research findings reveal that, as the number of freeze-thaw cycles increases, the ultimate bearing capacity of the test specimens exhibits a decreasing trend. Notably, when the number of freeze-thaw cycles accumulates to over 50 times, the magnitude of the decrease becomes more pronounced. Furthermore, concrete of higher strength and stainless steel tubes with thicker walls were found to markedly enhance freeze-thaw resistance, mitigating the loss of stiffness and ductility in the specimens. Based on regression analysis, a predictive model for the ultimate bearing capacity of CFSST stub columns under freeze-thaw conditions has been developed. Validation confirms that the proposed model achieves high accuracy in predicting the ultimate bearing capacity. The findings of this study provide a theoretical foundation for the design, performance evaluation, and maintenance of CFSST structures in cold regions. • Freeze-thaw degradation of CFSST stub columns is evaluated through axial compression tests. • Wall thickness and concrete strength significantly influence freeze-thaw damage resistance. • A predictive formula is developed to estimate bearing capacity after freeze-thaw cycles.