Numerical analysis of buckling behaviour of timber-encased steel composite columns under axial compression

Timber (e.g. Douglas-fir, spruce-pine-fir)-encased steel composite (TESC) columns provide a feasible application for timber in large-scale and high-rise structures. However, the load-carrying mechanism and buckling behaviour of TESC columns have not been thoroughly studied. This paper investigates the axial load distribution and buckling behaviour of TESC columns with embedded H-section steel through finite element (FE) analysis. FE models were built and validated by the experimental results. A parametric study was then conducted to assess the structural responses and load distribution of TESC columns with different geometric and physical parameters, including the steel area, timber area, slenderness ratio, steel yield strength and timber compressive strength parallel to grain. The numerical results revealed that increasing the slenderness ratio could enhance the confinement effect of the timber in improving the maximum load. A larger proportion of timber area provided a more significant confinement effect in enhancing the ductility of the steel, and then a minimum area ratio for TESC columns considering the confinement effect of timber was determined. Finally, the numerical results produced by 360 FE models of TESC columns were employed to evaluate the buckling curves of four current codes, and two new buckling curves for TESC columns were also proposed.