Experimental Study Of Cross-laminated Bamboo And Timber Columns Under Axial Compression

Cross laminated timber(CLT)is a new type of composite material which appeared in the 1990s.Because of its good mechanical properties,processing properties,natural environment characteristics and beautiful appearance,it provides the basis for the new building system.CLT’s gluing technology reduces the quality requirements of wood itself,so that more wood can be optimized and applied in the construction field.Cross laminated bamboo and timber(CLBT)is a new combination method based on the cross laminated bamboo and timber(CLT).It continues the characteristics of CLT,and improves the mechanical properties such as bearing capacity,stability and lateral stiffness.In this paper,CLT and CLBT columns are tested under axial compression.Through theoretical analysis and experimental research,the failure mode and ultimate bearing capacity of CLT and CLBT columns are obtained,and the mechanical performance indexes of CLT and CLBT columns are compared and analyzed.1)Cross-Laminated Bamboo and Timber(CLBT)column was composed of Glulam and SPF(spruce-pine-fir)wood.The material properties of CLT and CLBT columns were tested.The modulus of elasticity,compressive strength,failure mode and failure mechanism of CLT and CLBT columns were determined.The stress-strain relationship between the two materials was established.The test results show that the failure of CLT column is mild,which belongs to ductile failure;the failure of CLBT column is sudden,which belongs to brittle failure.2)Six groups of 18 CLT columns and CLBT columns were tested under axial compression.The failure modes of each group of specimens were compared and analyzed.The variation rules of vertical strain,transverse strain,lateral deflection and ultimate bearing capacity with slenderness ratio were studied.The failure modes and failure mechanisms of CLBT columns and CLT columns were discussed.The test results show that the ultimate bearing capacity of CLBT column is 40.49%～61.01%higher than that of CLT column,the lateral stiffness is also significantly improved,and the peak vertical strain is 30.45%～56.11%higher.3)Based on the analysis of the test data of CLT column and CLBT column under axial compression,combined with the design and calculation of CLT members in the design standard of wood structure,technical specification of glued timber structure and national design specification(NDS),the calculation formula for the bearing capacity of CLBT columns is derived.The analysis results show that the experimental values of CLBT and CLT are in good agreement with the theoretical values calculated by referring to the foreign wooden structure design specifications and the improved CLBT bearing capacity formula.The theoretical values calculated by CLBT and CLT are more conservative with the increase of the slenderness ratio of the test pieces.4)Using ABAQUS finite element analysis software,model the components of the axial compression test of CLT columns and CLBT columns,and perform eigenvalue buckling analysis and nonlinear buckling analysis under axial stress conditions,and compare and analyze them.The agreement between the stress,strain and lateral deflection in the column and the test value shows that the finite element simulation results agree well with the test results,indicating the feasibility of the finite element analysis.