Research on bias stress characteristics and influencing factors of concrete stacked columns with thin-walled steel tubes restrained by spiral ribs

Abstract

This study introduces an innovative spiral stiffener to mitigate the local buckling issue of thin-walled steel tubular concrete. In response to diverse restraint forms, 5 distinct specimen types were designed to probe the eccentric compression test. behavior & failure modes of the composite member. Test results: Spiral ribs limit steel tube buckling between stiffeners, reduce degree. Vs. ord. concrete-filled steel tube, bearing cap. up from 932kN to 1119kN (20% growth), safety margin from 1.48 to 1.84 (24% incr.). An empirical analysis of impact parameters was conducted, revealing that the pitch（ (Formula presented.) ） and width-thickness ratio of the spiral rib（ (Formula presented.) ） had a more pronounced effect on the damage morphology of the specimen. Design recommendations were provided: the diameter-thickness ratio of the steel pipe（ (Formula presented.) ）was limited to 110–150, the reinforcement rate((Formula presented.)) was between 0.8% and 2%, the pitch was 3.33 times the diameter of the specimen, and the width-thickness ratio of the spiral ribs was between 6 and 10. Through eccentricity((Formula presented.)) analysis, the damage limitations of this new component were determined to be approximately 0.5 eccentricity for both large and small eccentricities. Finally, based on superposition theory, a formula for ecc. compressive bearing cap. of new member type is proposed.