Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.

Compression Behaviors of Parallel Bamboo Strand Lumber Under Static Loading

In order to investigate the influence of length and compression directions upon behaviour of parallel bamboo strand lumber(PBSL)specimens,240 axial compression tests have been performed.With three similar one different typical failure modes,the mechanical performance for PBSL specimens under compression parallel to grain and perpendicular to grain are different as a whole.From the point of the characteristic values,the compression strength parallel to grain is 2.1 times of the compression strength perpendicular to grain.The elastic modulus for compression parallel to grain is 3.64 times of the compression strength perpendicular to grain.While the compression ratios along two compression directions are equal to each other.The bigger Poisson ratios for one typical side surface is 3.93 times of that for another typical side surface for PBSL specimens under compression perpendicular to grain,and the bigger value is equal to that for PBSL specimens under compression parallel to grain.Length can influence the mechanical properties of the PBSL specimens.The size 50 mm×50 mm×100 mm should be good choice for the standard or code to measure the compression strength.PBSL materials have better ductility under compression parallel to grain than that under compression perpendicular to grain.Stress-strain relationship models were proposed for PBSL specimens under compression parallel to grain and perpendicular to grain,respectively.These proposed models gave a good agreement with the test results.

Measurement of lumber moisture content based on PCA and GSSVM

Lumber moisture content(LMC) is the important parameter to judge the dryness of lumber and the quality of wooden products.Nevertheless the data acquired are mostly redundant and incomplete because of the complexity of the course of drying,by interference factors that exist in the dryness environment and by the physical characteristics of the lumber itself.To improve the measuring accuracy and reliability of LMC,the optimal support vector machine(SVM) algorithm was put forward for regression analysis LMC.Environmental factors such as air temperature and relative humidity were considered,the data of which were extracted with the principle component analysis method.The regression and prediction of SVM was optimized based on the grid search(GS) technique.Groups of data were sampled and analyzed,and simulation comparison of forecasting performance shows that the main component data were extracted to speed up the convergence rate of the optimum algorithm.The GS-SVM shows a better performance in solving the LMC measuring and forecasting problem.

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.

Effects of salinity on the nail-holding power of dimension lumber used in light-frame wood building

We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.

Effect of heating methods on drying quality of small-diameter birch lumbers

Following a normal low temperature drying schedule, the small-diameter Birch lumbers （ 1 000mm× 45mm ×30mm） were dried with consecution-heats or intermittent-heating, visual drying defects （bow, crook, twist, check along grain and end check） were measured, and then statistical analyses were performed. It was found that the drying quality of small-diameter Birch lumbers could be improved with intermittent-heating, but the intermittent time should be prolonged. Prolonging intermittent time helped to weaken or even avoid wood distortion and drying checks. It wash＇ t helpful in avoiding crook. The drying quality of small-diameter Birch lumbers with all kinds of drying methods reached the second class of the Chinese National Standard. The drying quality reached the first class of the Chinese National Standard with the intermittent-heating in the area of visual wood defects.

Viscoelastic Characteristics and Creep Prediction for Laminated Veneer Lumber

The viscoelastic characteristics of Aspen laminated veneer lumber (LVD were investigated with results revealing the dynamic creep behaviour under asymmetrical cyclic loading, which is analogous to solid wood under a static load. Curves for the creep indicated that after 10s cycles, the multiple correlation coefficient R2 for the 4-element, is more than 0. 98 in any instance, overwhelmingly well fitted to the data obtained. The mean square error of the 3-element viscoelastic model was 1 - 5 times higher than of the 4-ele-ment model under various cyclic loadings within a relative large loading range. The viscoelastic curves for LVL samples are nonlinear. They were linearized at some stress levels below 60% of their limited intensities. As loading was sustained for a longer period, the viscous flow was found to have a tendency of attenuation. The work absorbed by a specimen before the occurrence of creep failure, could be estimated in terms of failure appearance. Consequently, we could calculate the

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.

Study of drying of small diameter Larch lumbers with intermittent heating

Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously recorded and final drying defects were examined. The drying curves showed that the drying rate was a constant in the early stage of intermittent heating drying and decreased evidently when the MC was about 18% (intermittent 2h) and 20% (intermittent 6h). The drying quality reached the second (intermittent 2h) and first grade (intermittent 6h) of the Chinese National Standard. The visual drying defects, especially the check extent along grains were reduced with intermittent heating. When the intermittent time increased, the effect was more obvious.

Microwave Drying of Scots Pine Lumber:Structure Changes,Its Effect on Liquid Permeability

Microwave(MW)drying method was adopted to enhance the liquid permeability of Scots pine lumber.Structure changes were characterized by stereoscope microscope,scanned electron microscope(SEM)and transmission electron microscope(TEM)examination.Pore parameters before and after MW treatment were detected by mercury intrusion porosimetry(MIP)method,and the effect of structure changes on liquid permeability were analyzed.As stereoscope microscope,SEM and TEM examination results showed,macro and micro checks mainly developed at intercellcular of tracheids,intercellular of ray parenchyma and tracheid,while these checks extend main along the radial-longitudinal plane.Pit border destruction,aspirated pits’orus translocation and micro-checks in tracheid cell wall were also observed.MIP test shown that pore volume and pore area increased as macro and micro checks generated to form new cavities.Microstructure changes would increase the quantity of pores or enlarge the pore diameter.Liquid flow pathways increased as macro and micro checks generated,aspirated pits reopened to form new pathways;liquid flow efficiency improved as porosity,pore volume and pore diameter increased which facilitated the liquid flow.

Clinical features and surgical treatment of the coexistence of cervical,thoracic and lumber degenerative disease

Objective To discuss clinical features and surgical treatment of the coexistence of cervical,thoracic and lumber degenerative disease. Methods From January 2004 to December 2008,79 cases with the coexistence of cervical,thoracic

Dynamics of Lumber Production from Buttressed-Stumps of Logging Residues Using a Fuel Powered Horizontal Mobile Bandsaw Machine

Logging residue can be defined as any form of wood, which under the highest stage of technological development could be used in manufacturing but is left in the forest during logging. Lumber production from logging residues of a previous logging activity by a timber firm was undertaken with the objective of determining the suitability of utilizing buttressed-stumps as raw material for the timber industry. A horizontal mobile bandsaw machine was used to process the buttressed-stumps into lumber. The machine was characterized by a thin-kerr sawing technology （kerf-width 1.6 mm） compared to the conventional bandsaw machines of kerr-widths ranging from 3.0-4.5 mm. Lumber value and volume yields, fuel consumption rate, frequency of tool replacement and lumber production rate were assessed. Results indicated that there is the potential to increase timber production from logging residues by utilizing buttressed-stumps. Lumber value and volume yields of eight timber species investigated in this study ranged from 5%-31% and 34%-54% respectively. Fuel consumption rate which increased with increasing wood density, ranged from 5-14.5 liters/m3 of lumber produced. Frequency of saw replacement increased with increasing wood density. The number of saws required to produce one cubic meter of lumber, ranged from 1 to 7. Lumber production rate ranged from 0.10-0.38 m3/hour, increasing with decreasing wood density.

Observation of early active training effects after the operation for lumber intervertebral disc herniation

Objective To explore the recent and distant effects of early active training after the operation for lumber intervertebral disc herniation.Method 79 patients after the operation for mono segmental lumber intervertebral disc herniation had been divided into early active training group and routine control group randomly, and accepted training, regular re-examination, and follow-up of 1～6 years respedtively.Results The early active training group had better recent and distant objective effect, and more patients (97.6%) were satisfied with the operational effects.Conclusions The early active training after the operation for lumber intervertebral disc herniation is positive significant for operational effects.

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.

Application of finite element analysis in properties test of finger-jointed lumber

Finger-jointed lumber production has now become the most extensively used method for spliced lumbers jointing together endwise.The properties of finger-jointed lumber are affected by many different factors such as the end-pressure.The main mechanical properties to be tested for struc-tural use finger-jointed lumber include the modulus of elasticity in static bending and the bending strength.The most commonly used method for testing these properties at present is the experi-mental test.In this study,we used finite element method to investigate the end-pressure range,the modulus of elasticity in static bending and the bending strength for Pinus sylvistriv var.finger-jointed lumber under three different fitness ratios(0 mm,0.1 mm,0.3 mm).With finite element analysis(FEA)modelling results compared with the experimental test results,it is possible to find the relationship between these two kinds of results and use the FEA to predict the properties of finger-jointed lumber.The FEA applied in the end pressure tests showed a narrower range com-pared with the modelling results.It indicated that the FEA could be used in the prediction of the end pressure for finger-jointed lumber.The modelling results for modulus of elasticity(MOE)test and bending strength(MOR)test showed about 20%discrepancies compared with the experimen-tal results.Moreover,the MOE modelling results showed the same trend as experimental results under three different fitness levels while the MOR modelling results showed the different trend.It can be concluded that the FEA is a feasible way in analysing the properties of finger-jointed lumber if the errors could be eliminated properly.Some modifications should be made in order to realize the prediction of the properties of finger-jointed lumber more accurately.

Treatment of 120 Cases of Lumber Intervertebral Disk Displacement by Electroacupuncture plus Movable Cupping and Traction

Ashi points, movable cupping and traction were employed to treat 120 cases of prolapase of lumber intervertebral disk, and the total effective rate was 95.6%. Key Words Lumber Vertebrae - Electroacupuncture - Cupping Therapy - Acupuncture-moxibustion - Traction - Intervertebral Disk Dislacement Author: Lü Guo-ping (1958-), female, attending physicianTranslator: WU Xue-fei

Estimating Strength of Finger-jointed Dimension Lumber by Nondestructive Methods

Structural finger-jointed (FJ) lumber was used mainly in structural applications including glue-laminated beams and wooden I-joists and more recently in parallel chord wood trusses. The paper evaluated strength properties of structural FJ lumber by three nondestructive methods (edge-wise bending, longitudinal and transversal vibration) in order to find an alternative to traditional evaluation methods. Lumber was sawn from the logs following a pattern typically used in China to maximize the volume of recovered sawn timbers. After kiln-dried, these rough-sawed lumbers were planned to 4.5 cm thick, 9.0 cm wide and 100cm long. The lumber pieces were assigned to two groups (low-grade and high- grade groups) according to their dynamical modulus of elasticity. FJ lumber was produced by cutting a series of sloping fingers (finger length 20, 25 and 35 mm) on the end of the wood pieces to be joined and interlocking the two pieces. Each finger-jointed lumber with one same finger length had three types: L-L, L-H and H-H. The FJ lumber was nondestructively tested using edge-wise bending, longitudinal and transversal vibration methods. After three methods, tensile and bending strengths of FJ lumber were tested to build dynamical relationships between MOE and strengths. The results showed that dynamic MOEs were good indicators of the static MOE, but both dynamic MOE and static MOE had a bad correlation with tensile strength of finger jointed lumber.

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.