The flexural properties of young Pinus elliottii x Pinus caribaea var. hondurensis timber from the Southern Cape and their prediction from acoustic measurements

The objectives of this study were to determine the bending strength and stiffness properties of young Pinus elliottii x P. caribaea var. hondurensis timber from the Southern Cape, South Africa, and to evaluate the predictability of these properties from acoustic measurements on standing trees, logs and their sawn boards. The timber has good bending strength (MOR) properties but the mean stiffness (MOE_stat) was significantly lower than that required for structural-grade timber. The mean MOE_stat was also about 30% lower than a P. radiata control sample. The MOE_stat of sawn boards could be predicted from acoustic stress wave measurements on standing trees with a correlation (r) of 0.48 and from acoustic resonance frequency measurements on sawn boards with a correlation of 0.85. The MOR of sawn boards was not significantly correlated with acoustic stress wave measurements on standing trees and only moderately correlated with acoustic resonance frequency measurements on sawn boards (r = 0.45).     

Using acoustic wave velocity to select fibre-managed plantation Eucalyptus nitens logs for laminated veneer lumber products

The aims and objectives of this study were to investigate the potential to predict laminated veneer lumber (LVL) stiffness from wood properties measured on trees and logs, and determine variation in log, wood and veneer properties as a function of tree height and age. Log selections were made from trees in three stands that were planned for harvesting at 14, 20 and 21 years of age. Rotary peeled veneer recovery from the logs was on average 65%. After drying, Metriguard testing showed over 50% of the veneer had an estimated dynamic modulus of elasticity (MOE_dyn) above 12 GPa, with 20% above 14 GPa, and that veneer from the second log by tree height had higher MOE_dyn values. In visual assessment to the AS/NZS 2269.0:2012 Standard, no veneer could be utilised in a panels face or subface positions and the older-age stand provided almost four times the volume of usable veneer. Standing-tree acoustic wave velocity (AWV) explained a moderate amount of variance in log MOE_dyn and Pearson correlation coefficients between the (Metriguard) veneer MOE_dyn, log AWV, log MOE_dyn and disc basic density were significant, positive and strong, with log AWV explaining most of the observed variance in log stiffness. A moderately strong and positive linear regression existed between log AWV and veneer MOE_dyn, supporting the use of log AWV tools for the ranking of stiffness in fibre-grown plantation E. nitens logs. Mechanical strength testing of LVL studs extracted from panels manufactured from the trial’s veneer indicated they equalled, and for some tested parameters exceeded, the characteristic design strength values previously published by commercial LVL manufacturers for equivalent size pine products.     

Modulus of elasticity declines with decreasing planting density for loblolly pine (Pinus taeda) plantations

Context

Loblolly pine is often grown in intensively managed plantations for wood production. In order to fully evaluate the effects of management practices on wood quality and ultimately value, it is necessary to relate mechanical properties to management practices.

Aims

The aim of this study was to evaluate the effect of planting density on mechanical properties of lumber recovered from loblolly pine trees from a 27-year-old spacing trial and develop prediction equations for modulus of elasticity and modulus of rupture from stand, tree, and board characteristics.

Methods

Regression methods were applied to sample trees from three planting densities (2,989, 1,682, and 746 trees ha^?1) and used to relate mechanical properties of lumber extracted from the trees to stand, tree, and board characteristics.

Results

Initial planting density was found to be correlated with modulus of elasticity and, to a lesser extent, with modulus of rupture. Including board characteristics and utilizing the visual grade and board position as regressors produced improved prediction equations.

Conclusions

The mean modulus of elasticity declines with decreasing planting density while the variability increases, suggesting that planting density is a surrogate for frequency and size of knots. Thus, lower planting densities, while producing more lumber, may produce proportionally fewer boards of greater modulus of elasticity than higher planting densities.     

Mill variation in bending strength and stiffness of in-grade southern pine No. 2 2 × 4 lumber

Visually graded southern pine (SP) has wide variability within grade. For 2 × 4 lumber, this variability has increased because it is harvested from both natural forests and plantation forests where trees contain high percentages of juvenile wood. To investigate resource variability, six kiln-dried No. 2 2 × 4 SP packages were acquired from six mills. From each package, 124 samples were destructively tested in bending. Mean modulus of elasticity (MOE₁₅) ranged from 9.2 to 13.1 GPa, and three mills did not meet the design values (11.0 GPa). Bending strength (F _b) ranged from 7.6 to 11.9 MPa, and four mills did not meet the design values (10.3 MPa). Analysis of variance of MOE₁₅ and F _b showed significant differences between mills. MOE₁₅ explained from 33 to 51 % of the variability in F _b. These data suggest that variation between mills is high and destructive testing is critical for more accurate characterization of lumber properties.     

Variation of tensile strength with annual rings for lumber from the Japanese larch

To examine the effectiveness of long rotation forestry and the potential of complete utilization of Japanese larch (Larix kaempferi Carriere), we designed a tensile test using the lumber from six 87-year-old sample trees. Results showed that strength properties of lumber varied greatly in the radial direction within trees, but all sample trees showed a similar trend. There was little difference in dynamic Young's modulus but a large difference in tensile strength (TS) between the lumber and small clear specimens from undestroyed parts of the lumber. These differences decreased with an increase in ring number and became constant after 30 years. The presence and distribution of knots markedly affected the TS; and among the knot indices, the knot number (Kn) and knot area ratio of a maximum single knot (Km) proved to be effective for explaining the effect of knots. The distribution of Kn and Km in the radial direction agreed with the variation of TS in the radial direction. By investigating the variation patterns of lumber and small clear specimens in the radial direction, it was found that the strength properties of both required a long time, about 30 years, to reach a relatively constant state.Part of this report was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999     

Mill variation in bending strength and stiffness of in-grade Douglas-fir No. 2 2 × 4 lumber

Visually graded Douglas-fir (DF) has wide variability within grade. Variability for 2 × 4 lumber has likely increased because harvest has shifted from federal forests to private plantation forests that contain high percentages of juvenile wood. To investigate resource variability, six No. 2, 2 × 4 DF packages were acquired from six mills. From each package, 124 samples were destructively tested in bending. Mean modulus of elasticity (MOE₁₅) ranged from 9.8 to 13.4 GPa, and three mills did not meet the grade requirements (11.0 GPa). Bending strength (F _b) ranged from 5.5 to 11.3 MPa, and three mills did not meet the grade requirements (9.3 MPa). ANOVA of MOE₁₅ % and F _b showed significant differences at the 0.05 significance level. MOE₁₅ explained from 50 to 78 % of the variability in strength. These data suggest that variation between mills is high and destructive testing is critical for more accurate characterization of lumber properties.     

Genetic variation in wood color and its correlations with tree growth and wood density of <Emphasis Type="Italic">Calycophyllum spruceanum</Emphasis> at an early age in the Peruvian Amazon

Calycophyllum spruceanum (Benth.) Hook. f. ex K. Shum. is an important timber-tree species in the Peruvian Amazon Basin. Markets currently prefer wood with a uniform, light yellow color, but these preferences may change in the future. As farmers and industry commonly use wood from young trees, it is important to investigate genetic and environmental variation in juvenile-wood properties to assess whether tree improvement programs could make adjustments to changing preferences. A provenance/progeny test was established to evaluate genetic variation in growth and wood properties of young trees, the strength of their genetic control as well as their interrelationships both at the genetic and the phenotypic level in different planting zones. This paper presents analyses of variation in wood color at 39 months, and their correlations with tree growth and wood basic density. CIELab means for lightness ranging from black to white (L), green to red hues (a*) and blue to yellow hues (b*) were 67.63, 5.34 and 22.12, respectively; means for chroma (C) and hue angle (h)* were 22.76 and 76.43, respectively (C and h* were estimated from a* and b*). Significant variation due to provenances and especially due to families within provenances was found in some wood color characteristics, and some color characteristics also differed significantly among planting zones. Genetic correlations indicate that, in general, selection of faster growing trees and/or trees with denser wood would have little effect on wood color and its uniformity. In general, wood color had relatively low heritability (h _i ²): among all trees, h _i ² = 0.31 for L; and variance due to families was not significant for a* and b*. Genetic control of color was highest in the planting zone where trees grew most rapidly: h _i ² = 0.48 and 0.52 for a* and b*, respectively; but variance due to families was not significant for L. Results suggest that selection based on wood color would be more effective in zones with more fertile soils and higher rainfall.      

Differences of tensile strength distribution between mechanically high-grade and low-grade Japanese larch lumber 11: Effect of knots on tensile strength distribution

The tensile strength (TS) test results of Japanese larch (Larix kaempferi, Carriere) lumber of varying length have shown that the length effects on TS were different between high-grade (H) and low-grade (L) lumber. In this paper, we examined the effect of knots on the TS distribution by measuring the number of knots and the knot area ratio of each specimen. There were more knots in L than in H; and the knot area ratio in L distinctly increased as the length increased compared to that in H. The correlation coefficients between physical properties and TS indicated that knots were the most influencial factor for TS among several physical properties: annual ring width, distance from pith, density, dynamic Young's modulus, and knots. We attempted to estimate the length effect parameters by introducing the concept of assumed knot strength. We thought that the length effect parameters for 50th percentiles of TS could be estimated well with fitted 3P-Weibull, and that the parameters for 5th-percentiles could be estimated well with 2P-Weibull fitted to lower-tail 10% data by the likelihood method. The differences of length effect on TS between H and L should be governed by the presence of knots. The independent model based on the concept of assumed knot strength may express the TS of structural lumber of various lengths.     

Predicting the flexural properties of Chinese fir (Cunninghamia lanceolata) plantation dimension lumber from growth ring width

In this report, the 575 specimens were divided into ten groups based on range of growth ring width. The modulus of elasticity (MOE) and modulus of rupture (MOR) of 45 × 90 mm specimens of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation dimension lumber were analyzed by average growth ring width and average density of each group. The results showed that the average growth ring width was in inverse proportion to density, MOE, and MOR of the dimension lumber. Furthermore, average density was in direct proportion to MOE and MOR of the dimension lumber. The coefficient of determination (R ²) for all the regression equations ranged from 0.7340 to 0.9207 at a significance level of 0.001. However, without such group classification, there was poor relationship between growth ring width, density, MOE, and MOR with a determination coefficient of 0.0901–0.1855. This finding suggested that it was feasible to predict the flexural properties of Chinese fir plantation dimension lumber by average growth ring width after specimen group classification.     

Index selection for growth and construction wood properties in Pinus elliottii open-pollinated families in southern China

The initial introduction of Pinus elliottii (PEE) to China occurred in the 1930s, and the planting of this conifer species has now attained close to 3 million ha in the subtropical zone of southern China. A large-scale genetic improvement program for PEE was implemented in southern China to produce fast-growing trees with high wood quality to address the severe shortage of timber production over the last two decades. In this paper, selection for stem volume, basic wood density (DEN) and modulus of elasticity (MOE) was based on the Smith–Hazel index, and a total of approximately 2 000 individual trees from 158 PEE open-pollinated families were selected at 22 years of age. The DEN and MOE for each tree were determined by non-destructive evaluation techniques using the Pilodyn and Hitman Director ST300® acoustic velocity device. The heritabilities and genetic and phenotypic correlations for the traits that were measured were estimated using the residual maximum likelihood approach in the flexible mixed modelling program ASReml-R. The results showed that the heritability estimates for the wood properties were between 0.292 and 0.309, and the heritabilities of the growth traits ranged from 0.129 to 0.216. The genetic correlation between the DEN_P and acoustic velocity (V?) with MOE_P was 0.45 and 0.95, respectively. An indirect selection based on V was observed to be highly effective for determination of MOE. It indicated that V can be integrated into tree improvement programs as a useful index of MOE by ranking candidate families or individuals within the selection population. The genetic correlations between the growth traits and wood properties were not significant. By contrast, the phenotypic correlations between them were significantly positive, but the correlation coefficients were very low. The appropriate selection index (I₄), which placed 10 times as much weight on DEN and MOE as the equal emphsis method, was determined as the appropriate selection index.     

Prediction of bending properties for structural glulam using optimized distributions of knot characteristics and laminar MOE

This study established a prediction model for bending properties of glued-laminated timber (glulam) using optimized knot and modulus of elasticity (MOE) distributions of lumber laminate as the main input variables. For this purpose, knot and MOE data were investigated for all pieces of lumber that were prepared for glulam manufacturing, and statistical distributions of knot size, knot number in one lumber, and MOE of each laminate were optimized as distribution functions. These knot and MOE data were used as input variables in the prediction model for bending properties, and were also used in generating virtual glulam using the inverse transform method. Prediction of bending properties for glulam was carried out using the transformed section method, which is partially provided in ASTM D 3737 (Annex A4). Predicted values were compared with those from full-scale four-point bending tests for 60 six-layered glulams with 10 different laminar combinations. Finally, the allowable bending properties of glulam for each specific laminate combination were determined by calculating the fifth percentile of the modulus of rupture and the average modulus of elasticity from virtual test results of more than 1000 virtual glulams. From the results of this study, predicted bending properties for glulam and their distributions could be used for structural design in both allowable stress design and limit state design.     

Growth and dynamic modulus of elasticity of Pinus patula × Pinus tecunumanii hybrids in Mpumalanga,South Africa

Field establishment of South Africa’s most important commercial pine species, Pinus patula, is severely hampered by the pitch canker fungus, Fusarium circinatum. Importantly, hybrids between P. patula and other pine species tolerant to the pitch canker fungus, such as P. tecunumanii and P. oocarpa, have been identified as an alternative planting stock. In this study, variation in tree volume and dynamic modulus of elasticity (MOE_dym) of the P. patula × P. tecunumanii (low- and high-elevation [LE and HE] ecotypes) hybrid was compared with the P. elliottii × P. caribaea hybrid, and the pure species P. tecunumanii (LE) and P. patula. The MOE_dym was assessed using the Fakkop TreeSonic microsecond instrument across three sites. The results of the study showed that P. patula × P. tecunumanii LE performed significantly better than P. patula × P. tecunumanii HE for volume and MOE_dym, which in turn was significantly better than P. patula. The MOE_dym and tree growth decreased with an increase in elevation. There was significant taxon × site interaction for volume and MOE_dym. The results of these trials suggested that P. patula × P. tecunumanii LE is a suitable alternative to P. patula in the Sabie region of Mpumalanga in South Africa on frost-free sites, in terms of the traits that were assessed.     

Optimal timing of early genetic selection for sawn timber traits in <Emphasis Type="Italic">Picea abies</Emphasis>

In breeding Norway spruce, selection for improved growth and survival is performed at age 10–15 years in order to optimize genetic gain per year. We investigated whether a selection based on wood traits such as density and grain angle, measured under bark in the field at the same age would be informative enough with respect to structural quality traits of sawn boards. To achieve this objective, a sawing study was conducted on the butt logs of 401 trees from a 34-year-old Norway spruce progeny trial situated in southern Sweden. Stem discs were excised from the top of the logs and radial profile data of grain angle, and wood density was recorded for specific annual rings. The sawn and dried boards were assessed for structural traits such as twist, board density, bending stiffness (static modulus of elasticity, sMoE) and bending strength (modulus of rupture, MoR). Additive genetic correlations (r_a) between single annual ring density measurements and board density, sMoE and MoR were consistently strong (r_a>?0.7) for annual rings 5–13. Genetic correlations of similar magnitude between grain angle and board twist were estimated for all investigated annual rings (from 2 to around 26 under bark). Consequently, it was found that indirect selection for wood density and grain angle at the tree age 10–16 years would result in more genetic gain per year than selection at later ages. This makes it feasible to perform simultaneous selection of progeny in the field for both growth and wood traits at similar ages.     

Quality of timber products from Norway spruce

Summary Strength and stiffness together with some properties characterizing the stand and the growth of trees were studied. Specimens (45 × 70 × 2900 mm³) were cut from different radial and longitudinal positions, from fast-grown trees from two stands in southern Sweden. These trees had relatively large annual rings (4–6 mm) and were not representative of Norway spruce in Sweden but are an example of the intensivelymanaged stands which will probably constitute a substantial part of the raw material supply in the future.The results indicate that the mean values for strength and stiffness were lowest for the core studs and increased further away from the pith. This radial variation in strength and stiffness appears to be associated with the variation in ring width. Density alone, on the other hand, does not explain the radial variation but should be used together with either ring width or knot area ratio to explain the stiffness and strength respectively. The increase in the strength and stiffness of the core studs from the butt logs to the top logs was significant. Density alone was found to be the best variable to explain the longitudinal variation between the butt logs and the top logs. The heartwood formation in the butt log juvenile core appeared not to have a positive effect on strength and stiffness. The occurrence of compression wood, the magnitude of grain angle and the margin knot area ratio had only a minor effect on strength and stiffness.The authors gratefully acknowledge the support received from the EEC forest research programme, Contract no MA2B-0024, from NUTEK, project no 9100554 and from Södra Timber AB     

Wood properties and their among-family variations in 10 open-pollinated families of Picea jezoensis

This study aimed to evaluate radial and among-family variations of wood properties in Picea jezoensis. A total of 174 trees were randomly selected from 10 open-pollinated families in a progeny trial for measuring stem diameter, dynamic Young’s modulus of log (DMOE_log), annual ring width (ARW), air-dry density (AD), modulus of elasticity (MOE), and modulus of rupture (MOR). Mean values of DMOE_log, AD, MOE, and MOR were 9.60 GPa, 0.41 g/cm³, 9.44 GPa, and 76.6 MPa, respectively. Significant differences among families were observed in all properties. F values obtained by analyzing variance in wood properties were higher than those generally observed in growth traits. In addition, F values in wood properties remained relatively higher from the 1st to 25th annual ring from the pith, although F value in ARW rapidly decreased with each increase in annual ring number. These results indicate that genetic factors largely contributed to the variance in wood properties compared with the growth traits.     

Feasibility of near-infrared spectroscopy for online multiple trait assessment of sawn lumber

Near-infrared (NIR) spectroscopy coupled with multivariate analysis was applied to estimate multiple traits of sawn lumber. The effects of the lumber conveying speed (LCS) and measurement resolution of spectra (MRS) on the calibrations were examined. NIR spectra ranging from 1300 to 2300 nm were acquired at LCSs of 10, 20, and 30 m/min and at MRSs of 2, 4, and 16 nm. Prediction models of bending strength (F _b), modulus of elasticity in bending tests (E _b), dynamic modulus of elasticity (E _fr), and wood density (DEN) were developed using partial least-squares (PLS) analysis. LCS and MRS did not significantly influence the calibration performance for any wood property. The regression coefficients also showed no clear differences for any of the conditions. This indicates that the important explanatory variables included in the models are not greatly influenced by these measurement conditions. PLS2 analysis results, when presented graphically, allowed easy interpretation of the relationships between wood mechanical properties and chemical components, e.g., bending strength and stiffness were mainly related to polysaccharides cellulose and hemicellulose. NIR spectroscopy has considerable potential for online grading of sawn lumber, despite the harsh measurement conditions.     

The variation of microfibril angle in South African grown Pinus patula and its influence on the stiffness of structural lumber

Reduction in the rotation ages of softwood saw-log plantations in South Africa is causing increased proportions of low stiffness sawn lumber at final harvest. It has been shown for some species that the microfibril angle (MFA) of the S2 layer of tracheids is strongly related to the modulus of elasticity (MOE) of wood, even more so than wood density, especially in wood formed during juvenile growth. The objectives of this study were to describe the variation in MFA in young Pinus patula trees and to determine the relationship between MFA and the dynamic MOE of sawn P. patula lumber. Thirty 16- to 20-year-old trees from six compartments from the Mpumalanga escarpment were processed into discs and lumber. The MFA, density and ring width were measured at two height levels using Silviscan 3. The average annual ring MFA varied between 7° and 29°; the pattern of variation depended mainly on height level and the ring number from the pith. The MFA in P. patula followed the same within-tree variation trends as in New Zealand-grown Pinus radiata but the average MFA was lower in absolute terms and differences between height levels were less pronounced. The MFA and density exhibited highly significant Pearson correlations of 0.73 and 0.70, respectively, with board dynamic MOE. A multiple regression model, which included MFA, density and ring width, explained 71% of the variation in the dynamic MOE of boards. A sensitivity analysis on the model showed that MFA and density had approximately similar influences on predicting the dynamic MOE of Pinus patula boards.     

Twelve elastic constants of Betula platyphylla Suk

Wood elastic constants are needed to describe the elastic behaviors of wood and be taken as an important design parameter for wood-based composite materials and structural materials. This paper clarified the relationships between compliance coefficients and engineering elastic constants combined with orthotropic properties of wood, and twelve elastic constants of Betula platyphylla Suk. were measured by electrical strain gauges. Spreading the adhesive quantity cannot be excessive or too little when the strain flakes were glued. If excessive, the glue layer was too thick which would influence the strain flakes’ performance, and if too little, glues plastered were not firm, which could not accurately transmit the strain. Wood as an orthotropic material, its modulus of elasticity and poisson’s ratios are related by two formulas: μ ij/Ei=μji/Ej and μ ij<(Ei/Ej)1/2. The results showed that the elastic constants of Betula platyphylla Suk. measured by electrical strain gauges were accurate and reliable. The results of shear elastic modulus G _TL and G _LR show a high linear regression correlation coefficient (>0.95) between the reciprocal of elastic modulus MOE ⁻¹ and the square of the ratio of depth to length (h/l)², which indicate that shear modulus values measured were reliable by three point bending experiment.     

Effects of atropellis canker and stalactiform blister rust on the bending strength and stiffness of lodgepole pine lumber

Summary This study investigated the effect of Atropellis canker,Atropellis piniphila (Weir) Lohman and Cash, and stalactiform blister rust,Cronartium coleosporioides Arth., on the bending strength and stiffness of lumber from lodgepole pine,Pinus contorta Dougl. var.latifolia Engelm. The modulus of rupture, was unaffected by either disease. However, the modulus of elasticity (MOE) of lumber from infected trees, as determined by the Cook Bolinders and static bending tests, was significantly reduced from those of healthy trees. This impact should affect the use of lumber from infected trees when serviceability criteria govern the design of a structure. Should MOE-based, machine stress-rating of lumber become standard in the future, there may be an adverse, stress-related impact of these diseases on lumber value.We thank Mr. D. Hutcheson, B.C. Forest Service, Kamloops Region for advice and assistance, Messers, T. Jeanes, B. Geiselmann and D. Crabtree, Balco Forest Products Ltd., for advice, assistance, and particularly for harvesting and manufacture of the test material; Mr. L. Olsen, Forintek Canada Ltd. for assistance, and Dr. A. Harestad, Simon Fraser University for critical review. The research was supported in part by the Natural Sciences and Engineering Research Council, Canada, Operating Grant No. A3881     

Within- and between-stand variation in selected properties of Sitka spruce sawn timber in the UK: implications for segregation and grade recovery

Context

Information on wood properties variation is needed by forest growers and timber processors to best utilise the available forest resource and to guide future management.

Aim

This study aims to quantify the variation in selected properties of Sitka spruce (Picea sitchensis (Bong.) Carr.) structural timber.

Methods

Twelve harvest-age stands were selected, ten trees per site were felled and processed into 301 logs. Dynamic modulus of elasticity (MOE_dyn) was measured on each tree and log using portable acoustic instruments. Logs were processed into structural timber and its MOE and bending strength was determined.

Results

Overall, the timber satisfied the MOE, bending strength and density requirements for the C16 strength class. Approximately 25 % of the total variation in timber mechanical properties was attributed to between-stand differences, with the remaining 75 % attributed to within-stand differences. A series of equations were developed to predict site, tree and log-level variation in timber properties.

Conclusion

Knowledge of the site and stand factors that are associated with differences in timber properties can assist with segregation of the current resource. Portable acoustic tools can also be used to increase the stiffness of sawn timber by segregating out individual trees and logs that will yield low stiffness timber.