Lightweight concrete applied to concrete-filled steel tubular columns axially loaded

Abtract Given the growing demand for more efficient and rational construction systems, steel–concrete columns have emerged as an attractive structural solution due to the advantages of the combined action of the steel profiles and the concrete core. In this context, the use of lightweight structural concrete can significantly reduce the self-weight of structures because of its lower density. This study aimed to evaluate the structural behavior of axially loaded steel-concrete columns composed of cold-formed steel profiles filled with lightweight structural concrete produced with Brazilian expanded clay aggregate. The lightweight concrete presented an average compressive strength of 29.55 MPa and a density of 1510 kg/m³ . A total of 43 columns with rectangular cross-sections measuring 127 mm × 100 mm were tested. The steel profile thicknesses ranged from 1.5 mm to 3.0 mm, while the column lengths were 381 mm, 635 mm, and 1270 mm. All specimens were filled with lightweight structural concrete and subjected to concentric axial compression. In addition to evaluating the load-bearing capacity, the study investigated the failure modes and the influence of local and global slenderness parameters on the columns' structural behavior. The results showed that the predominant failure modes were local buckling of the steel profile and shear failure of the concrete core, with crushing core in some columns with 3.0 mm steel thickness. Profiles with greater thickness provided higher confinement indices, and higher thickness, contributing to improved structural performance of the composite columns. The experimental axial load capacities were also compared with predictions obtained from design standards, revealing values between 5% and 23% lower than those estimated by ABNT NBR 8800, Eurocode 4, and ANSI/AISC 360.