Eccentric compression behavior of thin-walled steel-tube/bamboo-plywood assembling short hollow column with binding bars

The development of laminated-bamboo has broadened the application range of bamboo material in the field of structural engineering.An assembling hollow column parallel to the fiber texture is composed of square thin-walled cold-formed steel-tube and bamboo-plywood by the fastening of the transverse binding bars and structural adhesive.The thin-walled steel-tube/bamboo-plywood assembling short hollow column with binding bars (SBCCBs) are a new type of steel/bamboo composite with excellent physical and mechanical properties.Multi-layered high-strength bamboo plywood forms the primary body in the SBCCB that is subjected to compressive forces, and the square thin-walled steel tube only serves as a liner.Large numbers of bamboo are used, which reduce the manufacturing cost of the composite columns and result in a relatively high load-bearing capacity.The failure modes, bearing capacity and influence factors of SBCCB subjected to eccentric compression loading, were investigated by the test of nine short specimens.The test results indicated that the compressive failure of specimens were primarily the gluing failure at the column end and the tension side of specimen, the gluing and debonding failure of the matrix interfaces in the middle of column between binding bars and the compressive broken of bamboo plywood material.The ultimate bearing capacity of SBCCB generally increased as the net cross-sectional area of gluing bamboo and hollow ratio increased, decreased as the slenderness ratio and the loading eccentricity increased.The thin-walled steel-tube embedded in the laminated bamboo column can enlarge the cross sectional area of composite column, and reduce the slenderness ratio and the loading eccentricity increased, which effectively improved the stability and ultimate bearing capacity of SBCCBs subjected to compression loading.The transverse binding bars forming the ferrule effect with the thin-walled steel-tube can effectively slow the gluing failure of SBCCB, changed the ultimate buckling mode and advantageously improved the compressive bearing capacity of specimens.The local buckling deformation decreased as the binding bars spacing decreased and can keep in a small range when the relative spacing ratio of horizontal binding bars to sectional size was below three.Compared to thin-walled steel-tube/bamboo-plywood assembling hollow column without the horizontal binding bars, the ultimate bearing capacity of SBCCB can be improved by 17.64%.A calculating model for the eccentric compressive bearing-capacity of SBCCBs, which can serve as a guideline for engineering applications, was obtained by nonlinear regression analysis of the test data, and the maximum error between the estimators based on the formula and the experimental results was about 8%.The overall results showed that the thin-walled cold-formed steel-tube and bamboo-plywood can form a composite structural element with good compressive performance, and the average compressive strength of this batch test specimens was 18.54 MPa.SBCCB specimens showed an excellent compressive performance and can be used as the vertical bearing element of the multi-story bamboo wood building structure.