Eccentric compression behavior of laminated bamboo-filled steel tube columns with different slenderness ratios

Driven by global building decarbonization and sustainable construction trends, laminated bamboo-filled steel tube (LBST) columns have emerged as a promising low-carbon alternative to traditional concrete-filled steel tube (CFST) structures. This study presents a comprehensive investigation into the eccentric compression behavior of LBST columns through an integrated experimental and numerical approach. Systematic uniaxial eccentric compression tests were conducted on 28 LBST specimens to elucidate the coupled effects of slenderness ratio ( λ ), relative eccentricity ( e 0 / D ), and steel tube thickness ( t ) on their ultimate capacity, failure mechanisms, and ductility. The experimental results reveal a transition in failure modes: from localized material crushing in short columns with small eccentricities to global flexural buckling in slender members with large eccentricities. Notably, the confinement provided by 4 mm and 6 mm steel tubes enhanced the core bamboo strength by 96.20 % and 126.82 %, respectively. Quantitatively, eccentricity and slenderness ratio were found to reduce the ultimate capacity by up to 62.67 % and 35.15 %, while significantly degrading initial stiffness. To verify the precision of the proposed model and further explore its performance across a broader parameter space, a high-fidelity finite element (FE) model was developed and validated against the experimental data, followed by a parametric extension involving 74 additional cases. The results confirm that the experimentally derived model maintains high predictive accuracy even under extended parametric conditions (R² = 0.9780). Finally, a normalized axial load-moment (N-M) interaction envelope is proposed, with its reliability and general applicability rigorously validated through the synergy of experimental findings and the expanded numerical database. This study provides a scientifically-grounded design criterion and a crucial theoretical foundation for the standardized engineering application of LBST columns.