A Review of Basic Mechanical Behavior of Laminated Bamboo Lumber

Over the past decade,the physical and mechanical performances of laminated bamboo lumber(LBL)–a bamboo-based structural material,have been extensively studied using experimental,analytical,and numerical approaches.This paper presents a review of existing knowledge in the literature about the mechanical properties of LBL.The paper involved the review of the response of LBL to different types of loading such as tension,bending,compres-sion,and shear.Based on results of the literature reviewed,the strength of LBL parallel to grain was 90–124 MPa with MOE of 10700 MPa in tension,29.55–72.60 MPa,and MOE of 8396–11022 MPa in compression,63.87–128.4 MPa,and MOE of 8320–10912 MPa in bending,and 7.15–17.5 MPa in shear.The average strength of LBL was similar and in some cases exceeded the average values of bamboo-or wood-based materials,while the variability of its mechanical parameters was lower.The variability in strength values of LBL was affected by bamboo species,density and thickness of bamboo strips,growth portion,type of treatment,strips arrange-ments,and type of adhesive which in turn calls for classification of LBL by strength grades,degree of hardness,the capability of impregnation and penetration,as well as by areas of application in construction.The study pro-vided and discussed concluding observations,the current research gap,and future research directions on the mechanical properties of LBL.

Nodes Effect on the Bending Performance of Laminated Bamboo Lumber Unit

This research studied the ultimate bearing capacity of laminated bamboo lumber(LBL)unit and thereby calculated the maximum bending moment.The load-displacement chart for all specimens was obtained.Then the flexural capacity of members with and without bamboo nodes in the middle section was coMPared.The bending experiment phenomenon of LBL unit was concluded.Different failure modes of bending components were analysed and concluded.Finally,the bending behaviour of LBL units is coMPared with other bamboo and timber products.It is shown that the average ultimate load of BS members is 866.1 N,the average flexural strength is 101 MPa,the average modulus of elasticity is 8.3 GPa,and the average maximum displacement is 17.02 mm.The average ultimate load of BNS members is 1008.1 N,the average flexural strength is 118.02 MPa,the average modulus of elasticity is 9.9 GPa,and the average maximum displacement is 18.26 mm.Laminated bamboo lumber(LBL)unit without bamboo nodes(BNS)has relatively higher flexural strength coMPared with LBL unit with bamboo nodes(BS).The presence of bamboo nodes reduces the strength of the entire structure.Three failure modes were concluded for BS members,and two failure modes were observed for BNS members during the experimental process.According to a coMParison between the LBL unit and other products,the flexural strength and bending modulus of elasticity of the LBL unit are similar as bamboo scrimber and raw bamboo components,which is much higher than timber components.

Slenderness Ratio Effect on the Eccentric Compression Performance of Chamfered Laminated Bamboo Lumber Columns

Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.

Constitutive Equation of Laminated Veneer Lumber (LVL) at Large Deformation Condition

The stress-strain relation of laminated veneer lumber (LVL) was established by the method of regression, and its constitutive equation at large deformation and constant loading conditions was given to predict the static mechanical behaviors of LVL.

Determination of coefficients of friction for laminated veneer lumber on steel under high pressure loads

In this study,static coefficients of friction for laminated veneer lumber on steel surfaces were determined experimentally.The focus was on the frictional behaviors at different pressure levels,which were studied in combination with other influencing parameters:fiber orientation,moisture content,and surface roughness.Coefficients of friction were obtained as 0.10–0.30 for a smooth steel surface and as high as 0.80 for a rough steel surface.Pressure influenced the measured coefficients of friction,and lower normal pressures yielded higher coefficients.The influence of fiber angle was observed to be moderate,although clearly detectable,thereby resulting in a higher coefficient of friction when sliding perpendicular rather than parallel to the grain.Moist specimens contained higher coefficients of friction than oven-dry specimens.The results provide realistic values for practical applications,particularly for use as input parameters of numerical simulations where the role of friction is often wrongfully considered.

Factors Influencing Bonding Strength of Laminated Bamboo Strips Lumber

Factors influencing bonding strength of laminated bamboo strips lumber (LBSL) were investigated in this paper. In order to find an optimized technology, this paper investigated how the thickness of bamboo strips, the assembly orientation of bamboo curtain, the type of adhesives, as well as coupling agent treatment of bamboo curtain affected the bonding strength. The following conclusions were drawn: 1)The thinner the thickness of the bamboo strips, the bigger the bonding strength of LBSL; 2) The assembly orientation of the bamboo curtain benefited the bonding strength, MOR and MOE; 3) The bonding strength increased with the use of phenol-resorcinol-formaldehyde (PRF) resin; and 4) Treatment of coupling agent could increase the bonding strength but decrease both MOR and MOE.