Axial compressive behavior of steel tube restrained bamboo columns with different slenderness ratios

Steel tube restrained laminated bamboo columns integrate the high strength and corrosion resistance of steel with the light weight and renewability of bamboo, offering considerable potential for application in energy-efficient and environmentally sustainable buildings. This study examines the influence of slenderness ratio on the mechanical behavior of laminated bamboo and steel tube restrained laminated bamboo columns. The results indicate that slenderness ratio markedly affects the failure mode, load-bearing capacity, and deformation behavior. Short columns predominantly exhibit end-strength failure, while medium and long columns fail through overall buckling. The stress–strain response of steel tube restrained laminated bamboo columns comprises elastic, elastic–plastic, and strain-softening stages. With increasing slenderness ratio, the axial compressive strength and initial stiffness of both types of columns decrease approximately linearly. However, steel tube restrained laminated bamboo columns demonstrate significantly enhanced resistance to the detrimental effects of slenderness due to the steel tube’s effective confinement of the core bamboo, particularly restraining lateral deformations. Consequently, the toughness coefficients of steel tube restrained laminated bamboo columns decline only marginally with increasing slenderness. The ultimate strengths of columns across various slenderness ratios were accurately predicted using Johnson’s parabolic empirical formula and a discount factor model.