Assessment of the anisotropic wood strength on local crushing

Abstract The effects of ring characteristics on the compressive strength and dynamic modulus of elasticity of seven softwood species in Taiwan were examined. The results revealed good correlation between compressive strength and dynamic modulus of elasticity obtained using an ultrasonic wave technique (correlation coefficient r=0.77–0.86). Overall, compressive strength increased with decreasing ring width parameters and increasing ring density parameters. Ring density was related to compressive strength, but was not the sole factor affecting the wood strength. According to our statistical analysis, compressive strength was affected by various ring characteristics. Relationships between ring characteristics and compressive strength are influenced by the anatomic direction. Results revealed that earlywood density and minimum density in a ring are equally important variables for evaluating the compressive strength of wood.

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Variability of spruce (Picea abies [L.] Karst.) compression strength with present reaction wood

Journal of Forest Science ◽

10.17221/13/2009-jfs ◽

2009 ◽

Vol 55 (No. 9) ◽

pp. 415-422 ◽

Cited By ~ 4

Author(s):

V. Gryc ◽

H. Vavrčík

Keyword(s):

Picea Abies ◽

Compression Strength ◽

Compression Wood ◽

3D Models ◽

Reaction Wood ◽

Stem Height ◽

Direction Parallel ◽

Strength Limit ◽

Wood Compression ◽

Wood Strength

The aim of research was to find out the variability of spruce (<I>Picea abies</I> [L.]) Karst.) wood compression strength limits in the direction parallel to grain. The wood strength was examined using samples from a tree with present reaction (compression) wood. The strength was found out for individual stem zones (CW, OW, SWL and SWR). The zone with present compression wood (CW) demonstrated slightly higher values of wood strength limits. The differences in the limits of compression strength parallel to grain in individual zones were not statistically significant. All the data acquired by measuring were used to create 3D models for each zone. The models describe the strength along the radius and along the stem height. The change of strength along the stem radius was statistically highly significant. There was an obvious tendency towards an increase in the strength limit in the first 40 years. With the increased stem height, there is a slight decrease in wood strength.

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Effect of stem bending on hydraulic conductivity and wood strength of loblolly pine

Canadian Journal of Forest Research ◽

10.1139/x94-060 ◽

1994 ◽

Vol 24 (3) ◽

pp. 442-446 ◽

Cited By ~ 13

Author(s):

T.S. Fredericksen ◽

R.L. Hedden ◽

S.A. Williams

Keyword(s):

Hydraulic Conductivity ◽

Loblolly Pine ◽

Modulus Of Rupture ◽

Vertical Position ◽

Sapwood Area ◽

Significant Damage ◽

Stem Bending ◽

Average Loss ◽

Wood Strength ◽

Increased Susceptibility

Stems of 30-year-old loblolly pine (Pinustaeda L.) trees were bent with a winch to determine the effect of bending, which might occur from severe wind stress, on the hydraulic conductivity and wood strength of tree stems. Stems were bent to a point of imminent stem failure and then released. After release, stems leaned an average of 6.25° from their original vertical position. Measurements of sapwood permeability and viable conducting area were made on stem sections cut from bent trees and were compared with sections taken from unstressed (control) trees. Dye was used to determine the percentage of functional conducting elements. An average loss of approximately 30% in conducting sapwood area was attributed to the bending treatment. Loss of functional conducting area was greater along the axis of bending than on the lateral sides of the stem perpendicular to the direction of bending. Damage was greatest on the compression side of the stem. Despite this damage, no difference was observed in sapwood permeability due to treatment. Modulus of elasticity and modulus of rupture were reduced by 19% and 34%, respectively, on the compression side of bent stems compared with control stems. Loblolly pine appears to be capable of sustaining significant damage to its water conducting system without compromising its hydraulic conductivity. However, reduced wood strength due to bending may result in increased susceptibility to wind breakage and (or) decreased commercial value.

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Woody material structural degradation through decomposition on the forest floor

Canadian Journal of Forest Research ◽

10.1139/cjfr-2017-0175 ◽

2018 ◽

Vol 48 (1) ◽

pp. 111-115 ◽

Cited By ~ 1

Author(s):

Shawn Fraver ◽

Mehdi Tajvidi ◽

Anthony W. D’Amato ◽

Daniel L. Lindner ◽

Jodi A. Forrester ◽

...

Keyword(s):

Mass Loss ◽

Structural Integrity ◽

Bending Strength ◽

Surface Hardness ◽

Strength Loss ◽

Carbon Accounting ◽

Pooled Data ◽

As Species ◽

Wood Strength

Dead woody material (DWM) plays numerous important roles in forest ecosystems; however, through the process of decomposition, it undergoes structural and chemical changes that progressively alter its function in these roles. Much remains unknown about how DWM mechanical strength and structural integrity change through decomposition in natural forest settings. We assessed changes in wood strength (bending strength, compressive strength, and surface hardness) using standard wood stakes of known initial mass from three species. The stakes were placed in forested settings for two and four years before collection for laboratory analyses. All three strength metrics decreased as stakes lost mass due to decay; however, bending strength had the strongest relationship with mass loss, a result that was consistent for all species, as well as species-pooled data. Results for all strength-loss metrics indicate that stakes had experienced ca. 10% strength loss before any detectable mass loss had occurred. Further, our results suggest that the decay class system typically used during field inventories — based in large part on tactile assessments of wood structural integrity — may provide a reasonable characterization of DWM mass loss, which is a critical assumption for carbon accounting and modelling based on inventory data.

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Practice for Establishing Clear Wood Strength Values

10.1520/d2555-98 ◽

1998 ◽

Author(s):

Keyword(s):

Clear Wood ◽

Wood Strength

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Influence of geometry on the stiffness of corner finger joints

BioResources ◽

10.15376/biores.14.2.2946-2960 ◽

2019 ◽

Vol 14 (2) ◽

pp. 2946-2960

Author(s):

Gourav Kamboj ◽

Vladimír Záborský ◽

Tomáš Girl

Keyword(s):

Wood Species ◽

Polyvinyl Acetate ◽

Beech Wood ◽

Bending Moment ◽

Elastic Stiffness ◽

Finger Joint ◽

Finger Joints ◽

Number Of Teeth ◽

Fagus Sylvatica L ◽

Wood Strength

Finger joints enable the full utilization of wood. The finger joint technique is used to eliminate wood defects that would otherwise weaken the wood strength. This research project evaluated how the wood species, adhesive type, and number of teeth affect the elastic stiffness of finger joints. The adhesives used were polyurethane and polyvinyl acetate, and the wood species were beech (Fagus sylvatica L.) and spruce (Picea abies L.). This study also determined the elastic stiffness of finger joints with 2 teeth and 5 teeth. For this purpose, the samples were loaded via a bending moment reaction, with tensile or compression forces in the angular plane. The highest elastic stiffness was obtained from the beech wood samples with 5 teeth bonded with polyvinyl acetate adhesive under tensile stress. Therefore, it was concluded that the elastic stiffness increased when the number of teeth increased. However, further studies on the elastic stiffness of finger joints are necessary in relation to the finger teeth length and surface area of the glue between the finger joint connections.

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The Chemistry of Wood Strength

Advances in Chemistry - The Chemistry of Solid Wood ◽

10.1021/ba-1984-0207.ch005 ◽

1984 ◽

pp. 211-255 ◽

Cited By ~ 24

Author(s):

JERROLD E. WINANDY ◽

ROGER M. ROWELL

Keyword(s):

Wood Strength

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The variability of wood density and compression strength of Norway spruce (Picea abies/L./Karst.) within the stem

Beskydy ◽

10.11118/beskyd201710010017 ◽

2017 ◽

Vol 10 (1-2) ◽

pp. 17-26 ◽

Cited By ~ 3

Author(s):

Petr Horáček ◽

Marek Fajstavr ◽

Marko Stojanović

Keyword(s):

Picea Abies ◽

Wood Density ◽

Compression Strength ◽

Wood Properties ◽

Stem Height ◽

The North ◽

Sample Tree ◽

Wood Compression ◽

Increasing Trend ◽

Wood Strength

This study relates to the variability of wood density and compression strength parallel to grain within the stem of spruce trees (Picea abies/L./Karst.). The sample tree originated from the Giant Mountains and was an adult autochtonous mountain spruce. The properties were analysed for wood that formed between 1850 and 1990 along (1) the north-south oriented radius and along (2) the stem height on test specimens with the following dimensions: 20×20×30 mm, prepared from logs taken from the stem base at distances of 2, 4, 6, 10, 14, 20, 22, 24 and 26 m. In individual sections, the properties of the samples oriented in the north or south direction did not differ, while the effect of different ages on the properties showed statistically significant differences at each orientation (p < 0.05). Along the radius, the properties showed an increasing trend in tree-rings that developed between 1850 and 1940 with a slight decrease in the following years. The coefficient of variation in various decades was 1–7 % (wood density) and 3–15 % (wood compression strength). Along the stem height, the properties gradually increased to a height of 20 m, while the increase in values was more pronounced in the 22–26 m interval. The variability of the wood properties along the stem height corresponded to the variability of the properties along the stem radius. A linear dependence between wood strength and density was demonstrated. Compared to what had been previously written, wood density showed a greater impact, probably due to the biomechanical optimization of the stem with regard to mechanical wind and snow loads in the mountains.

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Variation of the tree ring micro-hardness demonstrated on spruce wood

Journal of Forest Science ◽

10.17221/4608-jfs ◽

2012 ◽

Vol 50 (No. 3) ◽

pp. 135-141 ◽

Cited By ~ 1

Author(s):

V. Mareš ◽

J. Blahovec

Keyword(s):

Tree Ring ◽

Tree Rings ◽

Micro Hardness ◽

Growth Properties ◽

Mean Pressure ◽

Characteristic Points ◽

The Mean ◽

The Individual ◽

Wood Strength ◽

Weather Variations

Micro-hardness was used for the study of wood structure (Norway spruce) in the line perpendicular to tree rings (radial surface). The steel indentor 0.25 mm in diameter with flat head was used for this purpose. The individual penetration tests were performed at constant velocity 0.0167 mm/sinto a depth of 0.3 mm. Local wood strength was defined as the mean pressure on the indentor head at 0.02 mm penetration. The set of tests (~ 320) gave information about stress variation in dependence on the location of the test place in the tested surface. The stress was understood as a parameter describing the growth properties of wood similarly like the density usually used in dendrochronology. The measured strength variation is in agreement with visually observed tree rings. The acquired data made it possible to determine the mean characteristic points of the tree ring as well as the development of the parameters in dependence on the weather variations.

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