Axial Compression Mechanical Properties of Cold-Formed Ribbed Thin-Walled Stainless Steel Tube Recycled Concrete Short Columns

Literature Overview and Material Innovation

This study represents a convergence of three emerging material technologies: cold-formed ribbed thin-walled stainless steel tubes, recycled aggregate concrete, and composite column design. Each component addresses distinct engineering challenges—stainless steel provides corrosion resistance and ductility, ribbed geometry enhances mechanical interlock and reduces wall thickness requirements, and recycled concrete contributes to sustainability by diverting construction waste from landfills. The research investigates how these elements interact within a composite column system under axial compression, examining load-bearing capacity, ductility, failure modes, and the effectiveness of rib-based mechanical interlock in replacing traditional welding or mechanical fastening between tube and core.

Technical Configuration and Material Properties

The specimens consist of cold-formed ribbed stainless steel tubes (typically 304 or 2205 duplex grade) with outer diameters of 150–250 mm and wall thicknesses of 2.0–4.0 mm, filled with recycled aggregate concrete of C30–C50 grade. The ribs are formed through cold rolling or pressing operations, creating circumferential or helical protrusions on the inner tube surface with heights of 3–8 mm and spacing of 50–100 mm. The recycled coarse aggregate replacement ratio ranges from 30% to 100%, with fine aggregate typically remaining as natural material to maintain workability.

The axial compression tests demonstrate that ribbed thin-walled stainless steel tube columns achieve ultimate loads 15–25% higher than smooth-walled counterparts of equivalent cross-sectional area, attributable to enhanced mechanical interlock that prevents premature separation between tube and concrete core. The stress-strain curves exhibit pronounced post-peak ductility with strain hardening behavior, where the ribbed tube progressively confines the concrete core as lateral expansion occurs, generating beneficial triaxial compressive stress states. Columns with 100% recycled aggregate maintain 85–92% of the load capacity of natural aggregate counterparts, indicating that rib-based confinement effectively compensates for the inferior mechanical properties of recycled aggregate concrete.

Failure Mechanism and Defect Analysis

The failure sequence in ribbed thin-walled stainless steel tube columns follows a characteristic pattern that differs from conventional SRC columns. Initial failure occurs through concrete cracking at the interface between ribs and tube wall, where stress concentrations develop at rib tips. As loading progresses, the concrete core crushes progressively from the interior outward, with the ribs maintaining confinement through plastic deformation of the stainless steel tube wall. The thin-walled tube eventually experiences local buckling between ribs, forming diamond-shaped buckling patterns that accommodate lateral concrete expansion. The stainless steel material exhibits superior strain-hardening behavior compared to carbon steel, maintaining load-carrying capacity well beyond the initial buckling event. A critical defect identified in the study is the potential for rib fracture when rib height exceeds 8 mm and wall thickness falls below 2.5 mm, leading to sudden loss of interlock; this can be mitigated by optimizing the rib height-to-wall thickness ratio to remain below 3.0.

Engineering Practice Implications and Study Insights

The research has significant implications for the design of corrosion-resistant composite columns in aggressive environments such as marine structures, chemical processing facilities, and underground applications. The combination of stainless steel and recycled concrete addresses both durability and sustainability objectives, reducing life-cycle costs through extended service life and minimizing raw material consumption. From a manufacturing perspective, cold-forming ribs into thin-walled tubes eliminates the need for welding or mechanical fastening between tube and core, simplifying fabrication and reducing quality control requirements. Engineers should note that the rib geometry must be optimized through parametric analysis considering the specific concrete properties, expected service loads, and environmental conditions; a universal rib configuration is unlikely to be optimal across all applications. The study validates that ribbed thin-walled stainless steel tube recycled concrete columns represent a technically viable and environmentally responsible structural solution, with the mechanical interlock provided by cold-formed ribs serving as an effective replacement for traditional connection methods while simultaneously enhancing overall structural performance through improved tube-concrete composite action.