Experimental and theoretical analysis of L-shaped partially encased thin-walled steel-concrete composite columns under axial compression

Due to the advantages of aesthetic appeal and simplicity in construction, L-shaped partially encased thin-walled steel-concrete composite (thin-walled LPEC) columns present broad prospects in engineering applications. This study presented experimental and theoretical analysis of thin-walled LPEC stub columns under axial compression. The axial test revealed the axial failure modes of thin-walled LPEC columns: spalling and local crushing of concrete and local buckling of flanges. The parametric analysis showed that as the steel component thickness and steel yield strength increased, the transverse link spacing and limb height-to-thickness ratio decreased, the confinement of steel component and transverse links on the concrete was improved. Based on the axial stress state of the concrete, the concrete area was classified into un-effectively weakly confined, effectively weakly confined and strongly confined regions. A calculation method considering the influence of transverse link spacing and limb height-to-thickness ratio was proposed for calculating the concrete area in each region. According to the strain compatibility and interfacial interactions, a calculation model for lateral confining stress in concrete under peak load was constructed. The calculation method for the strength of confined concrete and the axial compression bearing capacity of thin-walled LPEC stub columns were proposed. The calculation results aligned well with the existing experimental and FE analysis results. This research lays a foundation for further exploration and application of thin-walled LPEC columns.