The axial compression mechanical properties and factors influencing spiral-ribbed thin-walled square concrete-filled steel tube composite members

Thin-walled concrete-filled steel tubular members have significant economic advantages, but are prone to local buckling, which has a great impact on structural safety. Therefore, this paper proposes a new spiral stiffened thin-walled CFST composite column to solve the above problems. The axial compression test found that spiral stiffeners can significantly improve the buckling resistance of thin-walled steel tubes, with the ultimate bearing capacity increased by 18 % and the ductility coefficient reaching about 2.0. Through the study of the mechanical mechanism, it is found that the spiral rib has little contribution to the vertical stiffness of the component, mainly by restricting the transverse deformation of the steel pipe to improve the mechanical performance of the component. At the same time, it is also found that the spiral rib can also play a strong constraint on the external concrete, and with a small amount of reinforcement, it can ensure the synergistic force of each part of the component. Based on the test, a parametric analysis was conducted on the pitch, the width-thickness ratio of the spiral rib and the influence law were quantified, and the design suggestions were provided. Finally, based on the fitting method, a formula for calculating the bearing capacity of this superimposed member was proposed. The new composite member has the advantages of less steel consumption, good mechanical properties, strong fire resistance, corrosion resistance, and good engineering application prospects.