Effect Of Wood Density Research Articles

Tension resistance properties of hold-down and angle-bracket connections on cross-laminated timber (CLT)

The goal of this study was to propose a practical approach for predicting the tension resistance properties of hold-down (HD) and angle-bracket (AB) connections on cross-laminated timber (CLT) by using modified design equations. The effects of wood density and number of screws on the tension properties of screwed HD and AB connections were experimentally investigated. Pine CLT connections with lower wood density exhibited lower tension resistance (−39%) and yield displacement (−34%) but higher ductility ratio (91%) relative to those of larch CLT connections. The AB connections on larch CLT exhibited lower elastic stiffness (−25 to −53%) and tension resistance (−10 to −22%) than those of the HD connections. The different load distributions of the HD and AB connections led to different failure behaviors associated with wood species. Although the tension resistance of the CLT connections was directly proportional to the actual number of screws, the elastic tension stiffness of the CLT connections was not directly proportional to the actual number of screws. Based on these experimental results, group effects on the tensile properties of the HD and AB connections on CLT were accounted for in the design equations, and the difference between the elastic stiffness, tension resistance, and ductility ratio values predicted using the developed design equations and the corresponding experimentally obtained values were 8, 6, and 7%, respectively.

Withdrawal capacity and strength of self-tapping screws on cross-laminated timber

The goal of this study was to investigate withdrawal capacity and strength of self-tapping screws (STSs) on cross-laminated timber (CLT). Effects of wood density, diameter, and penetration length on withdrawal behaviors of STS on CLT were evaluated. An equation was proposed to predict the withdrawal capacity of STSs on CLT. With a higher density of CLT, the withdrawal capacity and strength increased from 19.7 to 57.3%. Beneficial effects of a higher wood density of CLT on withdrawal behavior were reduced when STSs had large diameters (9 mm or 11 mm) and long penetration lengths (110 mm or 130 mm). With an increment of STS diameter from 5 mm to 11 mm, the withdrawal capacity increased from 5.7 to 27.7%, while the withdrawal strength decreased from 10.2 to 29.1%. When the penetration length was increased from 10 mm to 57 mm, the withdrawal capacity was increased significantly from 16.1 to 124.0%, whereas the withdrawal strength did not change significantly. A new format of prediction equation for the withdrawal capacity of STSs on CLT was proposed based on test results. The proposed prediction well reflected the withdrawal capacity of STSs with all test configurations, showing an average difference of 4.64% between predicted and experimental values.

Effects of density on colour and gloss variability changes of wood induced by heat treatment

AbstractThe influence of heat treatment severity (resulting from temperature) on the colour and gloss distribution changes of mahogany wood, and the effects of wood density on the responses to heat treatment were evaluated. The wood timbers with different densities were treated at 150°C to 200°C with an interval of 10°C and duration of 4 hours for heat treatment schedules. The colour parameters (lightness L*, red‐green axis value a*, yellow‐blue axis value b*) and gloss (parallel and perpendicular to the grain) values of heat‐treated wood were determined. The distributions of colour and gloss were analyzed using a frequency counts method. Results show that heat treatment resulted in the distinct decrease in L* and b*, while almost no change in a* for mahogany wood. The lower gloss values were obtained in the wood after heat treatment. The colour and gloss uniform on the exposed surface of the wood was improved due to heat treatment. Heat‐treatment induced colour and gloss changes were more effective in the samples with lower density. The effects of density on the colour and gloss variability in the original wood were reduced by heat treatment, and this reduction was more distinct at high heat treatment temperature. The total gloss change was found to be highly correlated with the total colour change of heat‐treated wood.

Effect of wood and panel density on the properties of lightweight strand boards

The objective of this study is to evaluate the effect of wood and panel density on the properties of lightweight strand boards (SB). For this purpose, we compared lightweight SBs made of low-density kiri wood (Paulownia tomentosa), medium-density pine wood (Pinus sylvestris) and high-density beech wood (Fagus sylvatica). Single-layer non-oriented SBs were manufactured with target densities of 300 and 400 kg m−3. Cohesion of beech boards was insufficient for further testing. The larger compaction ratio of kiri boards resulted in a steep density profile and mechanical properties, namely modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB), superior to those of pine boards. However, Kiri panels exhibited a higher thickness swelling (TS). MOR of kiri boards was 2.6 and 1.6 times higher than that of pine boards at 300 and 400 kg m−3, respectively, while these ratios were only 1.8 and 1.2 for MOE. We conclude that the effect of wood density on bending properties reduces as panel density increases and that the compaction ratio affects MOR more than MOE, which is mainly determined by panel density. Hence, utilization of low-density kiri wood allows reduction of board density with MOE being the limiting factor.

Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst)

A protective coating is often used on the cladding of wooden facades to limit the absorption of moisture. Low wood moisture content (MC) is essential to obtain satisfactory durability performance. ...

Effects of Wood Density on Aquatic Insect Communities in a Cuban Montane Rainforest Stream.

We tested whether hardness or different wood carbon densities, considered as the concentration of carbon structural compounds, influence functional feeding groups and species richness of aquatic insects in a tropical stream. We expected that harder woods would harbor aquatic insect communities with species richness and functional food group profile different from softwoods. We also expected that collector-gatherers and collector-filterers will be more abundant in softwood because harder woods are less substrate suitable for biofilm production. Aquatic insects associated with the following plants were analyzed: Gomidesia lindeniana with high-density, Psychotria grandis with medium-density, and Meriania leucantha with low-density wood. Diptera and Ephemeroptera were the most abundant groups sampled in the woods. Psychotria grandis shows higher concentrations of lignin, cellulose, and hemicellulose, followed by G. lindeniana and M. leucantha. Breakdown rates are different among plant species with M. leucantha having four times highest breakdown rates and on average three more species in the species richness value. We did not find significant differences in the composition of insect species associated with the plants. We found evidence that the richness and functional organization of aquatic insect communities were mostly related to the breakdown rates and lignin amount of the woods. Plants that decompose faster on average have three more species and two more insect functional groups. Our findings suggest that the loss of high carbon density trees in tropical forests can affect aquatic biodiversity.

Density of test bodies and its effect on burning rate of fire-retardant treated samples

The thesis focuses on the effect of wood density on the results of fire tests. Wood (spruce wood in particular) is one of the most commonly used materials in many sectors - building constructions, furniture manufacture etc. With such a broad application, its fire technical properties must not be neglected. Fire retardants should be therefore used to prevent the fire from occurring and spreading.

국내산 목재-콘크리트 복합적층재의 휨 크리프 성능

이 연구에서는 환경부하가 적은 산림훼손지 생태복원재료의 개발을 목적으로, 콘크리트와 국내산 침엽수 4종, 국내산 활엽수 3종의 제재라미나를 복합적층하여, 휨 크리프 성능에 미치는 수종의 밀도의 영향을 조사하였다. 목재-콘크리트 복합적층재의 휨 크리프곡선은 수종에 관계없이 시간에 따라 크리프곡선의 우측상변이 현저히 증가하는 형태를 나타내었고, 하중부하 후 약 30분 - 1시간 이후에서는 목재 및 목질재료와 같이 거의 직선적인 거동을 나타내는 것이 확인되었다. 목재-콘크리트 복합적층재의 초기변형은 수종의 밀도의 증가에 비례하여 변형이 감소하였고, 이 값은 콘크리트의 0.9 - 1.2배의 값을 나타내었다. 목재-콘크리트 복합적층재의 크리프변형은 콘크리트의 0.4 - 0.8배의 낮은 값을 나타내어 복합적층에 의한 콘크리트의 크리프변형의 현저한 감소가 확인되었다. 목재-콘크리트 복합적층재의 상대 크리프는 8.2 - 17.0%의 범위로 복합적층에 의해 콘크리트의 그것보다 0.3 - 0.7배의 매우 낮은 값을 나타내는 것이 확인되었다. 이 결과는 목재와 콘크리트의 복합적층에 의해 기존 콘크리트재료의 크리프변형을 감소시킨 산림훼손지 생태복원재료로 응용가능성을 나타낸다. In order to develop materials with a low environmental load for restoring the destroyed forest, seven types of wood-concrete hybrid laminated materials were manufactured with four softwoods, three hardwoods and concrete, and the effect of wood density on bending creep property was investigated. The bending creep curves showed a shape to considerably increase at the upper right side, and the curves were found to show a linear behavior beyond about 30 min - 1 hour, as behaviors of solid woods and wood-based materials. The initial compliances of wood-concrete hybrid-laminated materials decreased with an increase in the wood density, and those values showed 0.9 - 1.2 times of the concrete one. The creep compliances of hybrid laminated materials showed very low values, which were 0.4 - 0.8 times of the concrete ones. The relative creep were very low with a range from 8.2% to 17.0% range, which were 0.3 - 0.7 times of the concrete ones. These results indicate that these materials can be applied for restoring the destroyed forest to reduce creep deformation of the conventional concrete materials by hybrid-laminating concrete and woods.

Effect of wood density and water permeability on wood decomposition rates of 32 Bornean rainforest trees

Aims A better understanding of wood litter decomposition is essential for predicting responses of forest ecosystems to global climate change. Recent studies suggest that chemical properties of wood litters, rather than physical ones such as wood density, are more important for inter - We found large variation in the wood decomposition rate (a 49-fold range), suggesting that we need to consider this variation when cal- culating community-level carbon dynamics of tropical rain forests. The physical traits of wood, i.e. wood density and water perme- ability, were related to wood decomposition rate and its pattern over time. Decomposition half-time related positively and negatively to initial wood density and water permeability, respectively. The time-dependent- rate model fitted better for 18 species (56% of the study species) that had higher water permeabilities than the others, suggesting that micelle porosity in wood relates to temporal changes in decomposition rate.

Effect of Wood Density and Coating on the Tactile Sensation of Wood in Elderly and Young Person - On Kiri and Teak Wood -

The sensory tests by an elderly person and a young person were carried out by method of paired comparisons using coated kiri and teak wood (flat-sawn grain) without seeing the specimens. The properties of the palm of the hand and the heat flow from a metal disk heated at temperature of the palm to the specimen were measured. The density of wood influenced the sensory warmth and hardness of coated wood. The coating changed the tactile sensation of wood. The elderly person made more definite judgment regarding the sensory sliding than the young person, but the definition of judgment is the contrary in the sensory hardness. The comparison of the tactile sensation between elderly person and young person having the similar properties of palm showed that in the elderly person the decline of perceptivity on the sensory hardness was recognized, but wasn't on the sensory sliding. The heat flow from the heated metal disk to the specimen had a very close relation to the sensory warmth. The comfortable surface was different between the elderly and young person. The elderly person made more definite judgments regarding comfortability. The multiple linear regression analysis showed that the comfortability in the elderly person could be predicted by the sensory warmth.

3D multiscale micromechanical model of wood: From annual rings to microfibrils

A 3D micromechanical analytical-computational model of softwood, which takes into account the wood microstructures at four scale levels, from microfibrils to annual rings, is developed. For the analysis of the effect of the annual rings structure on the properties of softwood, an improved rule-of-mixture model, based on 3D orthotropic stress–strain relations and taking into account the compatibility of deformations at the interface of two phases and equilibrium of tractions at phase boundaries, is proposed. The improved rule of mixture model (IRoM) was compared with the classical rule-of-mixture (RoM) and finite element method (FEM) simulations. It was shown that IRoM gives almost as good results as FEM. The analytical model of annual rings is combined with the 3D finite element model of softwood as cellular material with multilayered, microfibril reinforced cell walls, developed by Qing and Mishnaevsky (2009a,b). Using the combined four-level model, the effect of wood density, microfibril angle (MFA) and cell shape angle (CSA) on the Young’s moduli, Poisson’s ratios and shrinkage properties of softwood has been investigated in numerical experiments. The simulations were verified by comparison with experimental data.

Factors Influencing the Production of Dust During the Hand Sanding of Wood

The effect of wood density and hardness, sandpaper grade, and contact pressure on the production of dust during the sanding of wood was investigated. The hardness and density of the wood correlated so well with each other that it was impossible to distinguish between the effects of each one. Harder woods produced a lower rate of dust production and finer dust, but the quotient of the mass of dust produced and the mass of wood removed varied little with wood type. Fine and coarse sandpaper produced similar concentrations of airborne dust, but coarse sandpaper produced less dust per unit mass of wood removed. Small samples of wood produced less dust per unit mass of wood removed than larger samples, but the benefit of this would be offset by the poorer efficiency of dust extraction systems in this situation.

Factors Influencing the Production of Dust During the Hand Sanding of Wood

The effect of wood density and hardness, sandpaper grade, and contact pressure on the production of dust during the sanding of wood was investigated. The hardness and density of the wood correlated so well with each other that it was impossible to distinguish between the effects of each one. Harder woods produced a lower rate of dust production and finer dust, but the quotient of the mass of dust produced and the mass of wood removed varied little with wood type. Fine and coarse sandpaper produced similar concentrations of airborne dust, but coarse sandpaper produced less dust per unit mass of wood removed. Small samples of wood produced less dust per unit mass of wood removed than larger samples, but the benefit of this would be offset by the poorer efficiency of dust extraction systems in this situation.