Axial compressive performance of cruciform timber-encased steel composite columns: Experimental investigation and buckling analysis through 3D laser scanning

Timber-encased steel composite (TESC) columns have garnered increasing attention owing to their high mechanical performance. However, limited studies focus on the compressive performance of cruciform TESC columns and the accurate evaluation of the full-field deformation of the embedded steel component. In this paper, a novel short cruciform TESC column embedded with the thin-walled cruciform steel component was proposed. 22 specimens including TESC columns, bare steel columns and bare glulam columns were tested under axial compression. Parameters including the width and the thickness of cruciform steel components were considered. 3D laser scanning technologies were applied to measure the full-field deformation of 20 steel members, thus quantitatively assessing the reduction in the deformation of steel components resulting from the lateral restraint of timber. Finally, a formula based on nonlinear fitting was established to predict the load-carrying capacity. The results showed that TESC columns exhibited significant enhancements in stiffness and load-carrying capacity. The lateral restraint of timber made the buckling modes of steel change from torsional buckling to mainly local buckling. Moreover, the high post-yield stiffness of steel components before reaching maximum load indicated that the timber offered sufficient lateral restraint to make full use of the steel strength. The 3D laser scanning method accurately measured the full-field deformation of the steel at the failure state. Compared to bare steel columns, the torsional rotation of steel components decreased by up to 83.14%, while the maximum absolute lateral deflection was reduced by up to 80.89%. The suggested strength formula offered sufficient accuracy in predicting the load-carrying capacity of short TESC columns, with the ratios between calculated and experimental values ranging from 0.908 to 1.120.