Experimental Investigation Of Wood Columns With Rectangular Cross Section

To improve the utilization ratio of timber,a kind of glued hollow wood column is proposed to replace the traditional solid wood column as the structural component.The SPF lumbers are used to manufacture the wood columns with a hollow cross-section.In this paper,the axial and eccentric compression tests of wood columns are carried out,the failure modes and failure mechanisms of the columns are analyzed,and the effects of slenderness ratio and load eccentricity on the load carrying capacity are studied.On this basis,the load carrying capacity calculation model of hollow wood columns under combined bending and compression is established.The following conclusions can be obtained:(1)The failure of slender columns under axial compression is characterized by buckling,while the failure of intermediate-slender columns is characterized by combined material failure and instability failure;the ultimate bearing capacity of axially loaded columns decreases significantly with the increase of slenderness ratio;the bearing capacity of slender columns can be calculated by Euler theory,while that of intermediate-slender columns is closer to the calculation results of tangent modulus theory and reduced modulus theory.Among the formulas for calculating the bearing capacity of axially loaded columns in the current design codes,the formulas proposed by the US Standard are relatively close to the experimental values.(2)The failure of eccentrically loaded columns is marked by the marginal strain reaching the ultimate tensile or compressive strain.Because of the different eccentricities of loads,the failure of columns can be divided into tension side failure(large eccentricities)and compression side failure(small eccentricities).Because of the different eccentric angles of loads,the shape of tension zone in the mid-height can be divided into trapezoidal and triangular.The ultimate bearing capacity significantly decreases with the increase of eccentricity.There is little influence of eccentricity angle on the bearing capacity of columns.(3)A mechanical model considering material and geometric nonlinearity is proposed for calculating the ultimate load-carrying capacity of hollow wood columns under eccentric compression.Based on the assumption of the height of neutral axis as the initial condition and the balance equation of internal and external forces as the judgment basis,the ultimate bearing capacity of members is calculated by the approximation method.The theoretical calculation results are basically consistent with the experimental results.The difference of ultimate bearing capacity between hollow and solid section members with the same consumables is calculated.The results show that the ultimate bearing capacity of hollow members is much higher than thatof solid section members with the same consumables.