Experimental Study On Pull-out Properties Of Laminated Bamboo Lumber Glued-in Rods In Parallel To The Grain

The traditional method of joining bamboo structures involves the use of metal plates,bolts,nails,and similar components.However,these metal parts are often exposed to air,resulting in unattractive joints that are prone to corrosion,rust,and reduced fire resistance.Consequently,these connection methods are inadequate for large-scale bamboo structures.A promising approach to enhance the strength and stiffness of bamboo structure joints is to adopt the glued rod joint method used in timber structures.This thesis begins by conducting tensile tests on specimens of side-pressure laminated bamboo lumber with glued-in rod joints.The test parameters include the edge distance of the glued-in rod,the thickness of the adhesive layer,the diameter of the glued-in rod,and the depth of the rod(length-to-diameter ratio).The effects of these parameters on the failure mode,pull-out load capacity,and deformation capacity of the glued-in rod joint are investigated.Based on the experimental results and existing studies,a bond-slip model is proposed for the side-pressure laminated bamboo lumber glued-in rod joint.Additionally,the stress analysis method is enhanced to formulate the pull-out load capacity equation for the joint.Furthermore,the Abaqus finite element software is employed to simulate the testing process and conduct parametric analysis.The main conclusions of this thesis are as follows:(1)Four typical failure modes are identified for the glued-in rod joint of side-pressure laminated bamboo lumber,including splitting of the laminated bamboo lumber and pull-out damage of the threaded rod,splitting damage of the adhesive layer of the laminated bamboo lumber,pull-out damage of the threaded rod,and yielding damage of the threaded rod.Experimental results indicate that the edge distance of the glued rod should be at least 4d to prevent splitting damage to the laminated bamboo lumber.An adhesive layer thickness of 1mm is too small,resulting in difficulties during construction and uneven adhesive distribution.On the other hand,adhesive layer thicknesses of 4mm and 6mm are too large,leading to the splitting of the adhesive layer in the laminated bamboo lumber.The optimal adhesive layer thickness is determined to be 2mm.For specimens with a threaded rod diameter of 12mm,pull-out damage occurs at an L/D ratio of 5,while threaded rod yield damage occurs at an L/D ratio greater than or equal to 10.All specimens with an 8mm threaded rod diameter experience threaded rod yield damage,while those with a 16mm threaded rod diameter undergo threaded rod pull-out damage.By utilizing the test results,a prediction equation for the load-bearing capacity of the side-pressure laminated bamboo glued rod joint is derived by incorporating the L/D ratio and threaded rod diameter as variables.(2)Building upon experiments and existing studies,a bond-slip model is proposed for side-pressure laminated bamboo lumber glued-in rod joints.This model effectively simulates the bond-slip behavior in such joints.An equation is developed to establish the relationship between average bond stress and the L/D ratio.The equation used to calculate the bearing capacity of the side-pressure laminated bamboo lumber glued-in rod joint is improved.The calculated values of the tensile bearing capacity obtained using the improved equation align well with the experimental values.(3)The simulation results from the Abaqus finite element software demonstrate good agreement with the experimental values,with only minimal error observed.This finding confirms the credibility of the finite element simulation method.Parametric analysis,based on the finite element model,reveals that positive stresses,tensile strains in the threaded rod,and stresses in the adhesive layer gradually decrease along the depth of the threaded rod insertion.The bond stress curve at the adhesive-bamboo interface exhibits a trend of high values at both ends and lower values in the middle,diminishing with an increase in adhesive layer thickness.The pull-out strength progressively increases with higher L/D ratios and larger threaded rod diameters within a certain parameter range.