Freeze-thaw effects on square CFST stub columns: Compression behavior and design

This paper focuses on the axial compression behavior of square concrete-filled steel tube (CFST) stub columns subjected to freeze-thaw cycles. Freeze-thaw cycles significantly affect the durability and performance of square concrete-filled steel tube (CFST) stub columns, especially in cold regions. The axial compression behavior of square CFST stub columns depends on the number of freeze-thaw cycles, concrete strength, and tube thickness. The compiled experimental database demonstrates that the detrimental effect of freeze-thaw cycles on ultimate bearing capacity becomes progressively more pronounced with increasing width-to-thickness ratio. Experimental investigations were carried out on nine square CFST specimens to further evaluate the axial compressive behavior of square CFST stub columns subjected to freeze-thaw cycles. Furthermore, finite element (FE) models were developed, and parametric studies were carried out. Results indicated that square CFST stub column typically fail due to local buckling of the steel tube and concrete crushing. Freeze-thaw cycles induce microcracks in the concrete and weaken the interfacial bond between the steel tube and concrete. Ultimate bearing capacity, ductility, and composite elastic modulus decreased with increasing the number of freeze-thaw cycles. A new design equation was proposed to predict the ultimate bearing capacity of square CFST stub columns subjected to freeze-thaw cycles. • Freeze-thaw cycles weaken the interfacial bond between the steel tube and concrete. • Ultimate bearing capacity, ductility, and composite elastic modulus decreased with increasing the number of freeze-thaw cycles. • An FE model of square CFST stub columns subjected to freeze-thaw cycles was established, and parametric studies were carried out. • Proposes a simplified design equation to estimate the ultimate bearing capacity of square CFST stub columns subjected to freeze-thaw cycles.