Compressive behavior of circular and square concreted-filled steel tubular short columns after freeze-thaw cycles

Abstract

In recent years, performance of concrete-filled steel tubular (CFST) short columns under axial compression after freeze-thaw cycles has gained attention for its long-term durability in colder climates. In the present study, freeze-thaw cycle test was conducted on the square section CFST (S-CFST) short columns to evaluate the influence of steel tube wall thickness and sectional dimension on the axial compression resistance of S-CFST short columns after freeze-thaw cycles. The infilled concrete strength degradation model and the calculation model for the axial compression resistance of the circular and square section CFST (C-CFST and S-CFST) short columns that can comprehensively consider design factors, such as the number of freeze-thaw cycles, concrete strength, and steel tube wall thickness, are proposed. Also, a parametric study is conducted to evaluate the accuracy and rationality of the prediction results of the existing models for concrete strength degradation and axial compression resistance of CFST short columns after freeze-thaw cycles. The existing experimental data and model parameter analysis indicate that as the steel tube wall thickness and concrete strength increased, the detrimental effects of freeze-thaw cycles on the in-filled concrete and the axial compression resistance of CFST short columns diminished significantly. The proposed model showed good accuracy and stability for predicting the axial compression resistance of C-CFST and S-CFST short columns after freeze-thaw cycles, without limitation of material strength range and the number of freeze-thaw cycles. Further, the infilled concrete strength degradation model was applicable to current design code models for the axial compression resistance of CFST short columns under normal temperature conditions, which estimated the axial compression resistance of CFST short columns after freeze-thaw cycles.