Physical and Related Properties of 145 Timbers
Chapters (6)
When providing physical data on a large number of wood species, as is the case here, it is imperative to specify by what method these data has been obtained. In addition, it is also necessary to provide some information on the material itself, its origin and method of handling. In the present study, the initial method used was that decribed by Pfeiffer (1927) although this was modified as the work progressed.
For all the species covered here, values for physical properties not given directly in the data sheets or graphs can be calculated from the data presented by means of simple formulae, most of which are also given in this publication. Examples of such calculations would include: the density at a moisture content other than that given; calculation of the density from the nominal specific gravity or vice versa; the maximum moisture content; void volume.
The moisture content of wood, as meant here and in general, is the weight of the water contained by a piece of wood, calculated in relation to the oven-dry weight of that same piece of wood and expressed as a %.
The left side graph on the graph page per species shows the hysteresis curves, while the right side graph displays the curves representing radial and tangential shrinkage and swelling. The shrinkage which can be expected to be displayed by green wood dried to a certain moisture content can be read directly from the graph.
Within the framework of the EC Research and Development programme “Wood as a Renewable Raw Material”(1983–1986), a number of European timber research centres, including the former TNO Timber Research Institute, participated in an integrated research project aimed at optimizing the use of European timber. This research concerned the manufacturing and applicability of 8 mm laminae for glued supporting constructions. Experiments were carried out for the manufacturing of parquet floors, table tops, cupboard shelves, beams, purlins, windows and doors. These semimanufactures, which were glued with resorcinol formaldehyde or urea formaldehyde, were given the product name LAMIC. In the graphs corresponding to these products the designation LAMIC is followed by the name of the wood species of which these products were composed.
... A larger variation of results (up to 10%) has been observed for the last two points with maximum relative humidity in both sorption and desorption isotherms which hygroscopic history of the materials is a major contributor in these variations (Lund Frandsen et al. 2007). Available isotherms for similar species are also demonstrated along with the results of this study in Fig. 7 (Nelson Jr. 1984;Rijsdijk and Laming 1994). As can be seen, the results have good correlations with the available data in the literature, whereas minor differences can be likewise attributed to differences in plantation location, location of the specimen within the tree, and type of treatment/postprocessing. ...
... As can be seen, the results have good correlations with the available data in the literature, whereas minor differences can be likewise attributed to differences in plantation location, location of the specimen within the tree, and type of treatment/postprocessing. For example, Rijsdijk and Laming (1994) compared the isotherm of laminated Norway spruce (Lamic) with sawn timber as presented in Fig. 7-a, which highlights the influence of treatment and postprocessing on sorption/desorption isotherms. It is noted that the proposed isotherm is established based on the calibrated porosity values for different pore groups per Table 3 and the calibrated sorption (nsi) and desorption (nei) exponents associated with each pore group per Table 4. ...
... Similar to softwood species, the sorption-desorption isotherms for different hardwood species tested (i.e. BB, PT and TO) along with some relevant isotherms in the literature (Hasburgh et al. 2019;Redman et al. 2016;Rijsdijk and Laming 1994) are compared in Fig. 8 with experimental data. The corresponding porosity and sorption/desorption exponents for different pore groups are included in the same Tables, i.e. ...
This paper proposes a unified sorption-desorption isotherm for the full range relative humidity (0-100%) based on categorizing the behaviour of different pore size groups for engineered wood products. The sorption and desorption isotherms are established by accumulating the wetting and drying behaviour of different pore groups, which qualitatively represent the physical structure of wood material. The porosity of wood is categorized into three distinctive pore size classes shown to be adequate for capturing the moisture capacity of different wood species with reasonable accuracy, and the saturation behaviour is studied separately for each pore type. Based on physical concepts, desorption isotherms are probabilistically derived from sorption behaviour. The proposed sorption-desorption isotherm is calibrated with experimental data conducted on seven engineered wood products including Pacific Teak, Tasmanian Oak, Blackbutt, Radiata Pine, Slash Pine, LVL of Radiata Pine, and CLT of Spruce. The relative humidity range for the active participation of each pore type in the moisture content is discussed, and further conditions for the simplification of the proposed isotherm is demonstrated.
... The MC at which all cell walls are fully water saturated, with theoretically no absorbed water in the cell cavities, is defined as the FSP (Skaar 1988). The FSP for most wood species is around 30%, but could be also as low as 19%, as in the case of African padauk, Ipe, or Wengé (Rijsdijk and Laming 1994). The widespreading FSP values are mainly attributed to existing differences in extractive contents (Wangaard and Granados 1967;Rijsdijk and Laming 1994). ...
... The FSP for most wood species is around 30%, but could be also as low as 19%, as in the case of African padauk, Ipe, or Wengé (Rijsdijk and Laming 1994). The widespreading FSP values are mainly attributed to existing differences in extractive contents (Wangaard and Granados 1967;Rijsdijk and Laming 1994). FSP is often considered as a value up to that physical and mechanical properties of wood are subject to change, with little changes at moisture contents above the FSP (Simpson and TenWolde 1999). ...
... Skaar (1988) stated FSP values between 25% and 30% (d.m.) for most temperate-zone wood species, but FSPs could also be much lower for many tropical wood species because of high extractive contents. Rijsdijk and Laming (1994) have reported for Wengé and African padauk a FSP of 19.5% and 17.0%, respectively. According to Choong and Achmadi (1991), extractives in cell walls influence only the water adsorbed at higher air RH levels, with the monolayer adsorbed water vapor not being affected. ...
Color including texture and gloss is one of the most important esthetical attributes of wood. For any porous materials in contact with water, the phenomenon of surface darkening arises from a change in the refractive index, as water enters air-filled pores. For the first time, this research investigated to what extent MC differences affect the surface color, below fiber saturation and after the pores are filled with water, with respect to extractive contents. Samples from 13 wood species were exposed to various climates, and as soon as EMC was reached, the color was determined. Color changes were also recorded after water submersion and also after vacuum impregnation in water. Chromaticity parameters a* and b* widely increased, along with higher moisture contents. Lightness changesweremostly stable at lower moisture contents.An exceptionwas demonstrated by the heartwood species black locust, plum, walnut, and oak, which showed a brightening effect at lowermoisture contents, followed by the darkening phase. The overall darkening of wood at high RH is connected to capillary condensation. Liquid water present in the cell lumen most caused darkening and an intensification of hue (increase in a* and b*). Darkening was even more expressed after vacuum impregnation with water. In conclusion, with only limited fluctuations in moisture contents below fiber saturation, the expected color changes are minor to neglectable.
... The MC at which all cell walls are fully water saturated, with theoretically no absorbed water in the cell cavities, is defined as the FSP (Skaar 1988). The FSP for most wood species is around 30%, but could be also as low as 19%, as in the case of African padauk, Ipe, or Wengé (Rijsdijk and Laming 1994). The widespreading FSP values are mainly attributed to existing differences in extractive contents (Wangaard and Granados 1967;Rijsdijk and Laming 1994). ...
... The FSP for most wood species is around 30%, but could be also as low as 19%, as in the case of African padauk, Ipe, or Wengé (Rijsdijk and Laming 1994). The widespreading FSP values are mainly attributed to existing differences in extractive contents (Wangaard and Granados 1967;Rijsdijk and Laming 1994). FSP is often considered as a value up to that physical and mechanical properties of wood are subject to change, with little changes at moisture contents above the FSP (Simpson and TenWolde 1999). ...
... Skaar (1988) stated FSP values between 25% and 30% (d.m.) for most temperate-zone wood species, but FSPs could also be much lower for many tropical wood species because of high extractive contents. Rijsdijk and Laming (1994) have reported for Wengé and African padauk a FSP of 19.5% and 17.0%, respectively. According to Choong and Achmadi (1991), extractives in cell walls influence only the water adsorbed at higher air RH levels, with the monolayer adsorbed water vapor not being affected. ...
Color including texture and gloss is one of the most important esthetical attributes of wood. For any porous materials in contact with water, the phenomenon of surface darkening arises from a change in the refractive index, as water enters air-filled pores. For the first time, this research investigated to what extent MC differences affect the surface color, below fiber saturation and after the pores are filled with water, with respect to extractive contents. Samples from 13 wood species were exposed to various climates, and as soon as EMC was reached, the color was determined. Color changes were also recorded after water submersion and also after vacuum im-pregnation in water. Chromaticity parameters a* and b* widely increased, along with higher moisture contents. Lightness changes were mostly stable at lower moisture contents. An exception was demonstrated by the heartwood species black locust, plum, walnut, and oak, which showed a brightening effect at lower moisture contents, followed by the darkening phase. The overall darkening of wood at high RH is connected to capillary condensation. Liquid water present in the cell lumen most caused darkening and an intensification of hue (increase in a* and b*). Darkening was even more expressed after vacuum impregnation with water. In conclusion, with only limited fluctuations in moisture contents below fiber saturation, the expected color changes are minor to neglectable.
... With a value greater than 2.5, as in this case, the deformation risk increases during the wood drying. 20 The swelling test results of Turkish hazelnut and other broadleaved native species in Turkey are given in Table 7. [21][22][23][24] The difference between tangential and radial swelling is 3.38%. When this value is greater than 3, as in this case, the risk of deformation increases during the wood drying. ...
... When this value is greater than 3, as in this case, the risk of deformation increases during the wood drying. 20 Although the risk of deformation is decreased with higher sorption values and a lower difference between radial and tangential sorption values, the deformation risk is increased with lower sorption values and a higher difference between radial and tangential sorption values. 20 The mechanical test results of Turkish hazelnut and some other broad-leaved native species in Turkey are given in Table 8. 17 The bending strength of Turkish hazelnut is moderate. ...
... 20 Although the risk of deformation is decreased with higher sorption values and a lower difference between radial and tangential sorption values, the deformation risk is increased with lower sorption values and a higher difference between radial and tangential sorption values. 20 The mechanical test results of Turkish hazelnut and some other broad-leaved native species in Turkey are given in Table 8. 17 The bending strength of Turkish hazelnut is moderate. But its MOE is low. ...
... The CFD model was based upon the fundamental phenomenon of pressurised CO 2 gas diffusion into an open wood cell lumen, as represented by a sap-filled capillary tube with diameter equivalent to the mean pore size, followed by depressurisation to cause liquid displacement due to gas bubble back-pressure. The theoretical amount of freewater associated with the open hydrofluidic network within the wood was estimated from wood anatomy, MC and mean basic density (Siau 1995;Rijsdijk and Laming 2006). Differences between theoretical and experimental dewatering when represented by an effective CO 2 diffusion coefficient (Deff) allowed a lumped-parameter ...
... kg/m 3 , and 127.4% (SD 9.7%) with a range of 86.3-162.1 kg/m 3 , respectively. The mean percentage saturation (Ross 2010) was calculated using a mean wood cell wall density of 1.54 g/cm 3 (Siau 1995;Rijsdijk and Laming 2006) and equalled 91.3% (SD 4.6%) with a range of 73.0-99.8%. Significant differences were observed for basic density, green MC and saturation with respect to tree number but not specimen position in tree (Table 2). ...
Supercritical CO2 offers an alternative method of removing wood moisture and reducing cellular collapse compared to traditional drying techniques. The technique has been previously demonstrated for Pinus radiata and Eucalyptus nitens dewatering and was modified in this study for New Zealand red beech (Nothofagus fusca) heartwood, which is notoriously difficult to dry without causing excessive distortion. The technique was also successfully extended to drying below the fibre saturation point. A specific dewatering and drying schedule was developed for N. fusca because of negligible dewatering using a schedule previously designed for wood with an open hydrofluidic network of interconnected vessels. An anatomical assessment confirmed lumen pathways were occluded with tyloses and polyphenol resins. A fluid dynamics assessment concluded that permeability measurements are recommended together with tortuosity and porosity information for improved wood species dewatering characterisation. Using the dewatering and drying schedule, collapse was successfully reduced by 92% for both normalised internal wood area and void collapse when compared to oven-dried samples. The beech specimens took 18 days to reach 17.3% moisture content (MC) but displayed some checking from early dewatering depressurisation, compared to air-dried control specimens which showed no collapse or checking but took 6 months to reach 12% MC. Supercritical CO2 dewatering and drying could be combined with extractives separation, preservative treatment, and mechanical forming of wood in one plant to make a potentially economically viable process with improved energy, environmental and carbon footprints. A techno-economic analysis is suggested to fully compare supercritical drying of wood against conventional drying operations.
... While factory-made composites are available with expected quality and specifications, in situ preparation of the reinforcement always involves uncertainty to a degree. On the other hand, timber quality widely varies due to its natural origin, which is further increased by factors such as moisture content, age, density, species, etc. Measured mechanical properties may show significant differences between samples even from the same species and are frequently only informative [4,5]. ...
... In this study, elastic behaviour is characterised by the general form of Hooke's law with nine orthotropic constants in the material stiffness matrix. Moduli parallel to grain were taken from the computation of this work, while the rest of the constants were adopted from literature [4,5,38,39]. ...
The strengthening of timber beams with carbon-fibre-reinforced polymers (CFRP) has been widely used in the last decades to enhance the behaviour of historical or new timber structures, usually for bending. While considerable improvement in capacity and ductility is typically achieved, the increase in stiffness was, in many cases, well short of analytical expectations, which tend to overestimate stiffness. This study addresses the problem by investigating the underlying mechanical behaviour using experimental, analytical, and numerical tools on a sample of Norway spruce (Picea abies) beams reinforced with carbon-fibre fabric. In the experimental program, each beam is tested for bending with and without CFRP reinforcement in order to determine specimen-specific stiffness increase on an individual basis. The reinforcement yielded an increase of 27% in capacity, 53% in ultimate displacement, and 133% in compliance, verifying its efficiency. Axial compression tests on an independent sample are also performed to verify modulus of elasticity in compression. Numerical computations based on a beam model and a three-dimensional finite element model are performed with the introduction of separate moduli of elasticity for tension and compression in timber. Inverse computation using the experimental load–deflection curves yielded the moduli and the compression yield stress of timber to provide the best match between tests and simulations. The mean difference of only 6% in stiffness between FEM and the tests is obtained. The dominance of normal stresses in the longitudinal direction is found, in correspondence with the experimentally observed tensile failure of timber (apart from a few defected specimens). Compression yield stresses are within 7% (beam model) and 2% (FEM) error compared with the control axial tests. The differences between FE simulations and tests in ultimate load and compliance are within 1%. This study concludes that the application of CFRP in the composite beams enables the determination of timber material properties opposed to pure timber beams without reinforcement, and the adoption of separate moduli of elasticity for tension and compression leads to adequate modelling of reinforced timber beams.
... The wood material requires a significant number of properties for its complete characterization. This wood species have specific characteristics, including Young's moduli, shear moduli, Poisson's ratios, compression yield stresses, tangent modulus, and maximum tensile strength, which are available in the literature (Green David, 1999;Rijsdijk and Laming, 1994;Okstad and Kårstad, 1985;and Kristian, 2009). The average material properties for the timber material are shown in Table 2. ...
... Average material properties for Nordic spruce timber (Green David, 1999;Rijsdijk and Laming, 1994;Okstad and Kårstad, 1985;and Kristian, 2009 sion, and it is used to simulate the anisotropic and asymmetric tension-compression behaviour for materials (Madenci and Guven, 2015). A bilinear anisotropic stress-strain relationship is used to enable the individual components of tension and compression to yield stresses. ...
The primary purpose of the pursued research presented in this article is to propose a new technique to create the actual three-dimensional geometry of knots and related fibre deviations and eliminate the inconsistency between modelling the knots as openings or solids. The geometrical and mechanical characteristics of knots and related local disturbed fibre patterns were numerically modelled. The numerical models were experimentally validated by four-point bending tests performed on six timber beams made of Nordic Spruce (Picea Abies). Tested specimens were sliced up into several strips parallel to the grains in the vicinity of the knot to numerically generate the actual geometrical model of the knots and related fibre deviations for creating the three-dimensional fibre paradigm. The validated numerical models can also be used based on visual inspections. The user needs only to define the position and size of the knot within the timber element required for the 3D finite element model. Moreover, the model allows defining different fibre patterns in the knot vicinity. Results proved that openings can represent knots when found in the tension zone with carefully adjusting the related three-dimensional fibre deviations. Moreover, the results emphasize the need for accurate modelling for the fibre deviations rather than the knot itself.
... The moisture content of the common European wood species at this point is generally assumed to be 30% (Siau 1984). Equilibrium moisture content (EMC) of reference wood species conditioned at fully saturated humidity (RH = 99%) agrees with observations of other authors (Baar et al. 2019;Laskowska et al. 2018;Nzokou and Kamdem 2004;Rijsdijk and Laming 1994). The variety of FSP values is mainly attributed to the differences in anatomical structures, the presence of extractives or other soluble compounds as earlier reported by Rijsdijk and Laming (1994) and Wangaard and Granados (1967). ...
... Equilibrium moisture content (EMC) of reference wood species conditioned at fully saturated humidity (RH = 99%) agrees with observations of other authors (Baar et al. 2019;Laskowska et al. 2018;Nzokou and Kamdem 2004;Rijsdijk and Laming 1994). The variety of FSP values is mainly attributed to the differences in anatomical structures, the presence of extractives or other soluble compounds as earlier reported by Rijsdijk and Laming (1994) and Wangaard and Granados (1967). ...
The mass loss kinetics of thermally modified wood species was analyzed as a time–temperature function. European beech (Fagus sylvatica L.), English oak (Quercus robur L.), Norwegian spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) wood specimens of dimensions 20 × 20 × 10 mm³ were thermally modified at 140 °C, 160 °C, 180 °C, 200 °C and 220 °C for 1–6 h using atmospheric pressure and superheated steam environment. The process intensity was determined by mass loss (ML), based on oven-dry mass before and after the thermal modification. Furthermore, the equilibrium moisture content (EMC) was determined before and after thermal modification to analyze the effect of mass loss on the sorption properties. Measured mass loss data were compared with the three-dimensional analytical function and its applicability to mass loss prediction was verified. For the studied wood species, the ML was found to be less than 1–1.5% when temperature of 140 °C and 160 °C was applied. Differences between studied species were more significant at temperatures higher than 160 °C. With the highest tested temperature (220 °C), mass loss reached 13.5% (beech), 18.8% (oak), 6.7% (spruce) and 13.5% (pine). According to the results, hardwoods have been shown to be more sensitive to the thermal degradation than softwoods as demonstrated by the higher mass loss recorded for the same modification time and temperature. The three-dimensional analytical function was confirmed as valid for all the species studied (R² = 0.89–0.99) and relevant for the mass loss prediction using fitted parameters. The EMC was reduced after thermal modification within the range of 4–48%, 0.4–47%, 1–32% and 0.7–40% for beech, oak, spruce and pine, respectively. Further, the EMC correlates exponentially (R² = 0.91–0.95) with the decrease in the specimens’ mass depending on the wood species used and modification temperature applied. However, the EMC seems to be almost stabilized beyond a limit value of approximately 10–12% of mass loss. The results provide a better insight into the mass loss and EMC kinetics of thermally modified wood species and can be used as a tool for prediction of mass loss values and required material properties (EMC) for designed wooden products.
... In line with this, Blohm et al. (2016) found that mature wood began to form around the age of 18 in Douglas-fir trees growing in plantations in Southern Germany. Wagenfür (2000) reported that Douglas-fir oven-dry wood density was 470 kg.m -3 while according Rijsdijk and Laming (1994) it was higher (492 kg.m -3 ). Nevertheless, the homegrown Douglas-fir oven-dry wood density was 419.7 kg.m -3 , in the USA (Pong et al. 1986). ...
... Furthermore, the average oven-dry wood density was 542.9 ± 66.3 kg m -3 and ranged between 402.7 and 648.9 kg m -3 . This resonates well with Wagenfür (2000) and Rijsdijk and Laming (1994) and confirms again the higher wood density of non-native Douglas-fir growing in Europe, in comparison with the home-grown trees. ...
The aim of the present study was to analyze the wood density variations along the stem radius of non-native Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) growing in Central Europe. Sample logs (0.5 m; breast height) were obtained from five Douglas-fir trees growing in the Czech Republic, to analyse the tree-ring widths (TRW) and the oven-dry wood density intra-species variability. The first 15 tree rings (close to the pith) were found to be 5.14 ± 1.68 mm wide, while the average TRW gradually decreased. The average oven-dry density of wood produced by non-native Douglas fir growing in the Czech forest was 542.9 ± 66.3 kg m-3 , which is notably higher than the home-grown Douglas-fir wood. Along the stem radius, from pith to bark, oven-dry wood density showed an upward trend.
... Izračunane absolutne vrednosti koeficienta nabrekanja za recentno smrekovino so v tej raziskavi nekoliko večje v primerjavi s povprečnimi vrednostmi iz literature (radialni 0,039 %/%, tangencialni 0,80 %/%; (Gorišek, 2009)). Pri recentni jelovini pa so bile izračunane vrednosti v radialni smeri nekoliko manjše, v tangencialni smeri pa primerljive s predhodnimi ugotovitvami (Kollmann in Côté, 1968;Noack in sod., 1973;Rijsdijk in Laming, 1994). Ifko (2016) je v raziskavi starega smrekovega konstrukcijskega lesa, starega med 160 do 180 let, zaznal nekoliko manjšo dimenzijske stabilnost v primerjavi s podatki iz te raziskave za smrekovino v 2. starostni kategoriji. ...
The influence of natural ageing on selected physical and mechanical properties of Norway spruce (Picea abies) and silver fir (Abies alba) structural timber was investigated. The wood was obtained from 10 buildings and dendrochronologically dated. The with ages were 95 to 391 years after felling. The chemical properties of the wood were analysed by FT-IR spectroscopy and the structural and histochemical properties by light and scanning electron microscopy (SEM), supported by energy dispersive X-ray spectroscopy (EDX). Colour was determined visually and instrumentally according to the CIELab standard. Physical properties included wood density, cell wall density, water vapour diffusivity, sorption properties, shrinkage and dimensional stability of the wood. The mechanical properties were determined statically using standard techniques and dynamically using ultrasound and vibration resonance method. The rheological properties of the wood were determined by static creep and mechanosorption tests. For aged wood, we confirmed a lower cell wall density compared to recently felled wood, a darker colour with a confirmed overall colour change (∆E*), whereby the colour lightness (L*) decreased significantly with the age of the wood. An increase in colour chromaticity (+a*, +b*) was observed in the earlywood and a decrease in the yellow hue (-b*) in the latewood. The relative proportion of hemicelluloses (RDH) decreased with wood ageing, while the degree of cellulose crystallinity (IK) increased and the O/C-ratio in the late wood of the spruce also increased. Local delaminations and radial microcracks were found in the cell walls of the aged wood. We found that aged wood of both species exhibited lower equilibrium moisture content (EMC) and hygroscopicity (Δs = -0.04 %/%) and lower cell wall saturation moisture content (FSP), while dimensional stability and diffusivity remained the same. Parallel to the grain, higher sound and ultrasonic velocities, lower damping, higher specific dynamic and static stiffness as well as higher tensile and specific compressive strength and hardness of the wood were confirmed in the aged wood. Bending strength and impact toughness are unchanged in aged wood. In the transverse plane, the aged wood exhibited a lower specific normal and shear stiffness and a lower specific hardness, tensile and specific shear strength only in the tangential direction. Relative creep and mechanosorptive deformations were lower in aged wood than in recent wood.
... ;Falemara et al. 2012;Tourunen 2018; Gérard et al. 1988;Allegretti and Ferrari 2007;Gerry and Miller 1954;Reyes et al. 1992;Rijsdijk and Laming 1994;Fabiyi et al. 2011;Bonoma et al. 2010;Jamala et al. 2013;Olorunnisola 2018;Simo Tagne 2014;Ngohe-Ekam et al. 2006]. ...
Triplochiton scleroxylon K. Schum, commonly named ayous in Cameroon, is a tree typical of secondary forests in subtropical areas mainly below 500 msl, characterized by an uneven distribution of annual rainfall and the presence of disturbance. This species is widely used in the origin area, and the interest of
European markets for ayous wood has steadily increased in the last decades. Despite the interest, only a few studies explored the characterization of this wood for its Cameroonian provenience. This study was carried out to provide a general overview of the available information and to determine some selected physical and mechanical properties of ayous wood coming from the department of Boumba et Ngoko in South-east Cameroon. Physical and mechanical properties and colourimetric parameters of ayous wood were determined following the UNI EN and ISO standards to characterize this wood and to compare with the data from literature. Density, 393 kg/m3 , resulted consistent with the data reported in the literature; the basic density was lower than those reported in the literature and the difference could be related to wood porosity; volumetric shrinkage was among the lower ones detected by other authors. Colourimetric parameters describing the undifferentiated creamy-yellow colour of the wood were L* 73.08, a* 7.39, b* 27.88. Mechanical properties were in the wide range of data reported by other authors; compression strength 36.6 MPa, static bending strength 61.1 MPa and Brinell hardness 12.2 N/mm2. These results extend our knowledge on the physical, colorimetric and mechanical properties of the ayous wood. These results can be helpful to highlight differences in the physical and mechanical properties due to the influence of origin on wood physical and mechanical properties. Future studies on this topic are needed to better understand the changes in properties and the characterization of the Cameroonian provenance. The results on the properties of ayous wood give an account of the real possibilities of treatments and technologies that can improve the technological characteristics and the environmentally sustainable use of this resource for the origin and importing countries.
... During the construction phase, often an initial gap of at least 1 mm is made, so that the connection is not too tight and difficult to mount. Subsequently, shrinkage of the wood materials due to changes in moisture content (MC), typically falling from 12% to 15% MC down to 6% to 8% MC (approximately 8% change) [7], may result in a longitudinal shrinkage of 4 mm to 6 mm for a beam element with a length of 5 m to 9 m, or approximately 2 mm to 3 mm at each end. This shrinkage is typically incorporated as a slip possibility in the connections. ...
Tolerance gaps in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to a substantial heat transfer to the metal connectors that are considered heat protected being embedded by the wooden components of the connection. Aluminium connectors are popular due to their ease of production and assembly, but they are particularly vulnerable to elevated temperatures. This study investigates the effects of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. Reduced-scale experiments were designed to study the temperature evolution of aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. For the 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36°C after 80 min, at which time the connector with a 1 mm gap had only reached 97 ± 1°C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection, in comparison to an equivalent tolerance gap without protection. Subsequently, two additional loaded fire tests were performed, for 6 mm and 22 mm tolerance gaps without fire protection, to investigate the critical failure mode of the connectors. In these cases, the failure occurred in the connectors at 87 min and 32 min, respectively, when their average temperatures reached approximately 315°C. This study demonstrates the critical influence of gap size on the fire performance of aluminium-wood joints.
... In the production phase, often an initial gap of at least 1 mm is made, so that the connection is not too tight and difficult to mount. Subsequently, shrinkage of the wood materials due to changes in moisture content (MC), typically falling from 12-15 % MC down to 6-8 % MC (approximately 8 % change) [5], may result in a longitudinal shrinkage of 4-6 mm for a beam element with a length of 5-9 m, or approximately 2-3 mm at each end. This shrinkage is typically incorporated as a slip possibility in the connections. ...
Tolerance gaps or slips in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to increased heat transfer through the connection. Aluminium connectors are becoming more popular due to their high malleability and availability, but they are particularly vulnerable to elevated temperatures. Thus, the objective of this study is to investigate the effect of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. An experimental campaign was designed to study the temperature evolution of the aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. The results showed a clear and consistent impact of the connection gap size on the temperature evolution of the aluminium connectors. For the larger 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36 °C after 80 minutes, at which time the connector with a 1 mm gap had only reached 97 ± 1 °C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection after 40 minutes of fire exposure, in comparison to an equivalent tolerance gap without fire protection. This study shows that tolerance gaps can lead to a significant reduction in the capacity of aluminium connectors, but this may be mitigated with additional fire protection.
... The wood properties vary widely based on various factors, including species, age, moisture content, density, and location. Properties can also vary from one sample to another and are frequently mainly indicative [8][9][10][11]. The elastic limit in tension and the material's nonlinear compression behaviour are key characteristics of the overall bending behaviour. ...
This research presents a parametric three-dimensional finite element study on the effects of closely spaced knots and related fibre deviations on the flexural failure mechanism of wood. The model considers the effects of the position of the knots along the beam's longitudinal and vertical axis. The numerical models were validated by bending tests performed on six beams. The actual three-dimensional geometry of knots and related fibre deviations were determined accurately based on an algorithm proposed previously by the authors. The elastic-plastic constitutive law of Nordic Spruce wood was considered based on the Hill anisotropic model. The failures were numerically predicted with the help of the Tsai-Wu failure criterion. The validated numerical models can also be used based on visual inspections. The user needs only to define the position and size of the knots and the space between them. Moreover, the model allows defining different fibre patterns in the knot vicinity. The model considers a fixed knot located in the tension zone at the mid-span of the beam and a moving knot adjusted at horizontal and vertical centre-to-centre distances d and v from the fixed one. Results revealed that regardless of the distance d (where v = 0), the failure will initiate at the same load levels for both knots. However, moving the adjacent knot diagonally (v not equal to 0) causes shear failure between the knots. The part of the clear wood between the knots is ineffective if the knots' centre-to-centre distance is less than three times the knot diameter.
... The manufacturer provides specifications for either the fibres or the prefabricated fibre-matrix composites in CFRP. However, in the case of wood, characteristics vary greatly depending on various parameters such as the species, age, moisture content, density, location, etc. Properties can also differ from sample to sample and are frequently just suggestive [41][42][43][44]. The elastic limit in tension and the material's nonlinear compression behaviour are critical parameters in the overall bending behaviour. ...
The application of fibre-reinforced polymers (FRP) for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. Over the last few decades, several reinforcing materials and techniques evolved, and considerable progress was made in numerical modelling, especially using the finite element method. As this field of research has become extensive and diversified, as well as numerous contradicting results have emerged, a thorough review is necessary. This manuscript covers the topics of historical preliminaries, reinforcing with carbon and glass fibre composites, bond characteristics, main reinforcing techniques, modelling of knots, and the effects of the fibre waviness on the composite behaviour. A detailed overview is given on the experimental and numerical investigation of mechanics of strengthened beams. A one-of-a-kind table is presented that compares the stiffness improvement observed in several studies with analytical estimates. Attention is drawn to a number of challenges that have arisen, e.g., the moderate stiffness enhancement, composite-to-wood interface, modelling of knots, and strengthening of defected timber members. This paper can be used as a starting point for future research and engineering projects.
... The most efficient way for the protection of wood by photoirradiation is a pigmented coating, in which no photochemical degradation occurs (Böttcher 1984). As far as the exterior applications of wood are a concern, the role of moisture content varies between the ranges of 8% and 40% by mass and affects dimensional changes between 2% and 10% depending on wood materials (Rypstra 1995;Rijsdijk and Laming 1994). To explain the influence of moisture content in wood, particularly biological and chemical degradation such as cracking, swelling, shrinking, erosion and freezing, there are some studies including permeability measurements for wood coating films (Ahola et al. 1999;Wassipaul and Janotta 1972;Schneider 1975;Ahola 1991;Hora and Böttcher 1993;Hora and Bottcher 1994;Derbyshire and Miller 1997), the percentage of moisture monitoring on wood panels (Teichgräber 1973;Sell 1982), high scale construction by wood (Sell 1985;Hjort 1997), and computer simulations (Bancken and Frencken 1997;Derbyshire and Robson 1999). ...
Flame retardants mitigate the threat of fire from inherently flammable wood and wood products responsible for sustaining a high standard of living. Wood is one of the aesthetically pleasing, highly sustainable as well as eco-friendly materials. It is not only an integral part of structures, but also the main source of home appliances, furniture, industrial applications, and offices all over the world. The coating provides protection to wood materials against outdoor weathering, photochemical degradation, and fire. Therefore, to minimize the degradation of wood for the increasing long life and survival ability, various coatings were synthesized and applied to enhance their performance for the wood application. This review provides a historical overview that leads to the structural properties of wood and the most promising surface treatments that will help pave the way for developing more effective and non-intrusive flame retardants in the future.
... Besides the reduction in density, also the water sorption properties of both wood and bark were heavily affected by chemical pre-treatment ( Figure 8). The sorption behavior of untreated poplar wood, with moisture content between 8 and 21% in the range of climates studied, was as expected according to literature (Rijsdijk and Laming 1994). Surprisingly, the corresponding moisture content values of bark were clearly higher than for wood. ...
The thermal insulation properties of bark and wood of a poplar tree (Populus nigra × alba) were investigated using a guarded hot plate device (GHP) and a purpose-built miniature heat flow meter (Mini-HFM). To reduce their density and improve their performance as insulation material , bark and wood were chemically treated. The correlation between thermal conductivity and test temperature as well as between thermal conductivity and material moisture was investigated. By means of the treatment 44 and 34% of the mass of bark and wood, respectively, was removed and the equilibrium moisture content of the both materials decreased significantly. For untreated bark, a thermal conductivity of 0.071 Wm −1 K −1 and 0.140 Wm −1 K −1 , respectively , were determined in transverse and axial direction. For wood, measurements showed comparably higher conductivities of 0.078 Wm −1 K −1 and 0.204 Wm −1 K −1 in transverse and axial direction. By reducing density, thermal conductivity of bark decreased up to 24%, whereas for wood reductions between 10 and 35% were found. It was shown that the self-constructed Mini-HFM is a useful and reliable instrument to determine the thermal conductivity on a small wood sample in the three main anatomical directions.
... Keylwerth and Noack (1964) presented established sorption isotherms as well. Moreover, both adsorption and desorption processes can be used, as utilized by Rijsdijk and Laming (1994) and Patera et al. (2016). Rode and Clorius (2004) and Melin et al. (2016) described a methodology to set up humidity-and temperature-dependent adsorption and desorption planes for a temperature range of −12°C to 50°C. ...
A timber bridge constructed in 1815 was renovated in 2018, wherein the load-bearing system was reinforced with beech laminated veneer lumber (LVL) elements. Beech LVL is primarily found in dry and heated structures (Service Class 1). Although the material of this bridge would not be directly exposed to weather, it would be exposed to outdoor relative humidity ranging between 50% in spring and 90% or higher in autumn (Service Class 2). Thus, the moisture content development in the reinforcements was monitored to observe the response of the material under such conditions. The moisture content was measured using both sorptive and electrical resistance methods. The relationship between the electrical resistance of the material to moisture content and sorption isotherms was determined through laboratory experiments. Thereafter, the derived relationships were used to determine the moisture content measured on the bridge over a period of two years. Consequently, the two measurement methods resulted in overlapping of moisture content values, which remained within safe levels and are expected to be maintained in future. The overlapping moisture content measurements validated that either of the monitoring methods could be independently deployed to obtain reliable results.
... Sycamore maple (Acer pseudoplatanus) was used for all the presented experiments. We calculated the specifications for each layer of boards according to reference values from literature (Sonderegger et al. 2013;Rijsdijk et al. 2010), for attaining a predicted radius of 420 mm. 0 • 14000 0.0001 * As a result of the orientation, the active layers take into account the radial direction, whereas the passive layers take into account the longitudinal direction. ...
We present a hybrid approach to manufacturing a new class of large-scale self-shaping structures through a method of additive fabrication combining fused granular fabrication (FGF) and integrated hygroscopic wood actuators (HWAs). Wood materials naturally change shape with high forces in response to moisture stimuli. The strength and simplicity of this actuation make the material suitable for self-shaping architectural-scale components. However, the anisotropic composition of wood, which enables this inherent behavior, cannot be fully customized within existing stock. On the other hand, FGF allows for the design of large physical parts with multi-functional interior substructures as inspired by many biological materials. We propose to encode passively actuated movement into physical structures by integrating HWAs within 3D-printed meta-structures with functionally graded stiffnesses. By leveraging robotic manufacturing platforms, self-shaping biocomposite material systems can be upscaled with variable resolutions and at high volumes, resulting in large-scale structures capable of transforming from flat to curved simply through changes in relative humidity.
... The FSP is generally considered as 28% to 30% moisture content. It is not a xed point and it may vary in different species from 19% to 30% [31]. Both species in the present study achieved FSP in the 15%-20% range for moisture content. ...
Prosopis juliflora is an invasive plant species rapidly expanding in the Asian and African continents. Invasion of P. juliflora in Bundala Ramsar Wetland (BRW) in Sri Lanka has created a number of biodiversity and conservation issues. This study was conducted to assess the possibility to utilize this invasive plant as a fuel source for local industries. The moisture content, wood density, ash content, volatile matter, fixed carbon content, biomass/ash ration and calorific value of P. juliflora were measured and compared with Leucaena leucocephala, which is a widely used fuelwood source in Sri Lanka and elsewhere. P. juliflora, performed better than L. leucocephala for most of these parameters. Ash content was comparatively higher in P. juliflora than that of L. leucocephala; however, biomass to ash ratio of P. juliflora was significantly lower (at 0.05 level of significance) than that of L. leucocephala, suggesting its suitability as a fuelwood source. Further, the Fuel Value Index (FVI) of P. juliflora (3,276) was slightly lower than that of L. leucocephala (3,336), a non-significant difference. P. juliflora and L. leucocephala reached Fiber Saturation Point values within drying periods of 24 and 27 days, respectively. According to our estimates of energy properties, 1 Kg of P. juliflora could be used to substitute 0.5 L of diesel and furnace oil as well as 5 kWh (5 units) of electricity. As such, we recommend harvesting P. juliflora from BRW as a potential fuelwood energy source for local industries.
... The FSP is generally considered as 28% to 30% moisture content. It is not a fixed point and it may vary in different species from 19% to 30% [31]. Both species in the present study achieved FSP in the 15%-20% range for moisture content. ...
Prosopis juliflora is an invasive plant species rapidly expanding in the Asian and African continents. Invasion of P. juliflora in Bundala Ramsar Wetland (BRW) in Sri Lanka has created a number of biodiversity and conservation issues. This study was conducted to assess the possibility to utilize this invasive plant as a fuel source for local industries. The moisture content, wood density, ash content, volatile matter, fixed carbon content, biomass/ash ration and calorific value of P. juliflora were measured and compared with Leucaena leucocephala, which is a widely used fuelwood source in Sri Lanka and elsewhere. P. juliflora , performed better than L. leucocephala for most of these parameters. Ash content was comparatively higher in P. juliflora than that of L. leucocephala ; however, biomass to ash ratio of P. juliflora was significantly lower (at 0.05 level of significance) than that of L. leucocephala, suggesting its suitability as a fuelwood source. Further, the fuel value index of P. juliflora (3,276) was slightly lower than that of L. leucocephala (3,336), a non-significant difference. P. juliflora and L. leucocephala reached Fiber Saturation Point values within drying periods of 24 and 27 days, respectively. According to our estimates of energy properties, 1 Kg of P. juliflora could be used to substitute 0.5 L of diesel and furnace oil as well as 5 kWh (5 units) of electricity. As such, we recommend harvesting P. juliflora from BRW as a potential fuelwood energy source for local industries.
... All rights reserved because the logs were already air dried, volumetric shrinkage due to water loss should be considered. To correct the shrinkage, a volumetric shrinkage value was applied (derived from a literature review see (Rijsdijk & Laming 1994)). We obtained the log volume as averaged cross-sectional areas (i.e. ...
1. The importance of wood decay for the global carbon and nutrient cycles is widely recognized. However, relatively little is known about bark decay dynamics, even though bark represents up to 25% of stem dry mass. Moreover, bark presence versus absence can significantly alter wood decay rates. Therefore, it really matters for the fate of carbon whether variation in bark and wood decay rates is coordinated across tree species.
2. Answering this question requires advances in methodology to measure both bark and wood mass loss accurately. Decay rates of large logs in the field are often quantified as loss in tissue density, in which case volume depletions of bark and wood can give large underestimations.
3. To quantify the real decay rates, we assessed bark mass loss per stem surface area and wood mass loss based on volume-corrected density loss. We further defined the range of actual bark mass loss by considering bark cover loss. Then, we tested the correlation between bark and wood mass loss across 20 temperate tree species during 4 years of decomposition.
4. The area-based method generally showed more than 3-fold higher bark mass loss than the density-based method (even higher if considering bark cover loss), and volume-corrected wood mass losses were 1.08-1.12 times higher than density-based mass loss. The deviation of bark mass loss between the two methods was higher for tree species with thicker inner bark. Bark generally decomposed twice as fast as wood across species, and faster decaying bark came with faster decaying wood (R2=0.26, P=0.006).
5. We strongly suggest using corrected volume when assessing wood mass loss especially for the species with faster decomposable sapwood and all the wood at advanced decay stages. Further studies of coarse stem decomposition should consider trait “afterlife” effects of inner bark and estimate fraction of stem bark cover to obtain more accurate decay rates.
6. Our new method should benefit our understanding of the in situ dynamics of woody debris decay and monitoring research in different forest ecosystems worldwide, and should aid meta-analyses across diverse studies.
中文摘要
1. 倒木广泛存在于森林生态系统中，其分解动态对全球碳和养分循环均发挥着重要作用。树皮与树干的干物质含量比约为1:3，因此树皮和树干的分解速率对碳循环均有显著影响，但对树皮分解的研究却鲜有报道。仅有的少量研究发现，树皮能调控树干分解，但是树皮与树干的分解是否广泛地跨物种相关尚未见报道。
2. 采用正确的方法来测定树皮和树干质量损失是解决这些问题的关键。在野外实践中，大型倒木的质量损失通常通过密度损失来替代，但树皮和树干在分解过程中均有较大程度的体积损失，且随分解程度加深而逐渐增大，这直接导致基于密度的质量损失低于真实值。
3. 本研究选取20种欧洲常见的温带树种并通过4年野外定位分解实验分别测定树皮、树干密度损失，树皮单位面积质量损失，树干经体积修正后的密度损失。旨在提出能准确测定倒木质量损失的有效方法，并进一步探究树皮和树干分解速率是否跨物种显著相关。为进一步提高树皮质量损失测定的精确度，本研究将树皮覆盖度随分解的损失纳入计算。
4. 结果表明，基于单位面积测定的树皮质量损失数值是密度方法的3倍，若考虑树皮覆盖度损失将会得到更高的偏差；经体积修正后的树干质量损失是密度方法的1.08-1.12倍。经两种方法测定的树皮质量损失的差值与内树皮的厚度显著正相关。跨物种而言，树皮质量损失是树干质量损失的2倍，并且树皮易分解的树种往往具有易分解的树干(R2=0.26, P=0.006)。
5 .因此，在测定树干质量损失时，边材易腐的树种和处于较高分解程度的所有树种均建议进行体积修正；在测定树皮质量损失时需要考虑内树皮的“死后效应”和树皮覆盖度损失。
6. 本文提出的测定方法广泛适用于多种生态系统下的原位分解实验和野外调查实验，并期待为荟萃分析和模型预测等提供更为系统且精确的数据支撑。
... Hacimsel daralma yüzdelerine göre hırnık ağacı "hacimsel daralması orta derecede", zeytin ve yenidünya ağaçları ise "hacimsel daralması fazla olan ağaçlar" sınıfında yer almaktadır [35]. Teğet yöndeki daralma yüzdesi fazla, radyal yöndeki daralma yüzdesi düşük olan ağaç türlerinin radyal-teğet daralma ortalama değerleri arasındaki farkın 2,5'den fazla olduğu ve bu ağaç türlerinde kurutma sırasında ahşapta deformasyon oluşma riskinin arttığı belirtilmektedir [45,46]. ...
ABSTRACT In this study, physical (density, shrinkage and swelling percentage), mechanical (compression strength parallel to grain, static bending strength and modulus of elasticity) and surface properties (surface roughness and color parameters) of stem woods of Diospyros lotus, Olea europaea and Eriobotrya japonica fruit trees grown in Turkey were investigated. The technological properties of experimental specimens obtained from the stem woods of these trees were determined according to the relevant standards. According to the obtained results, it was found that stem woods of all the fruit trees were in heavy trees class. The volumetric shrinkage percentages of the stem woods of Olea europaea and Eriobotrya japonica were found to be higher than that of the Diospyros lotus, and Eriobotrya japonica stem wood had the highest swelling percentage. In addition, it was determined that all three fruit trees were in the class of big trees in terms of compression strength parallel to the grain, they were in the class of small trees in terms of modulus of elasticity, and the mechanical properties of Eriobotrya japonica stem wood were highest. Olea europaea stem wood had a rougher surface than others and Diospyros lotus had a lighter colored wood than the others. Consequently, it is recommended that, three fruit tree stem woods could be evaluated some places where the processing properties are important and require high strength because of their high density, high compression strength parallel to grain and the small modulus of elasticity.
... Analyzing the process of wine absorption in wood in more detail, it is important to note that the liquid absorbed in the heartwood remained mainly below the fiber saturation point (FSP), so liquid absorption by heartwood appeared to be governed by water diffusion rather than capillary flow (Johansson & Kifetew, 2010), which depends on the microstructure of hardwood (Salin, 2011). It was observed that when wood was moistened below its FSP, a swelling of the wood occured that caused dimensional change between 1% and 2%, preferably in the radial and tangential directions (del Alamo-Sanza et al., 2016; Rijsdijk & Laming, 2011). This could explain the readjustments in the shape of the barrel that gave rise to abrupt pressure variations in the first few hours (see Fig. 4) with the sudden rupture of the vacuum that was generated then and which caused a gradual loss of vacuum. ...
The process of aging red wines in barrels is a common practice that aims to improve the quality of the wine. Oxygen, together with the compounds released by the oak wood, is responsible for this improvement through interaction with the wine compounds during the process. Wood as a natural product presents a series of highly significant discontinuities in its characteristics, not only between trees of the same species, but even between different areas of the same log. It is not surprising that, despite the homogenization of the characteristics of the wood due to the number of staves in a barrel (around 30 pieces), barrels made from the same batch of wood show very different behavior when aging the same wine. This work presents the results of applying a new way of classifying wood in cooperage by means of image analysis of the staves, based on its anatomical characteristics besides grain and handling of the staves, in order to achieve the production of barrels with a desired oxygen transfer rate (OTR) potential and also with great homogeneity between manufacturing batches. The two batches of barrels built with high and low OTR proved to be very homogeneous and the oxygen dosage of the high OTR barrels was more than twice that of the low OTR barrels, which confirmed the success of the system developed.
... The moisture content as well as swelling and shrinking values between different equilibriums are well known for different wood species 10 . Less information is available for the speed of moisture change and the related dimensional change within the sorption process. ...
An investigation of simultaneous dynamic mass and length change measurement for wood is presented. In contrast to the equilibrium in moisture content and swelling and shrinking, where extensive data exists for different wood species, less information is available for the dynamics of moisture changes in direct comparison to the related dimensional changes during the sorption process. This is due to a lack of methods. A gravimetric sorption system, equipped with a high resolution camera and an automated image evaluation, is used to examine simultaneous effects of water vapour sorption dynamics and dimensional change. This method proves a strong correlation between mass and dimensional change, which is in contrast to other investigations. Equilibrium moisture content as well as swelling and shrinking data is in good agreement with literature and manual measurements. The method enables the possibility to determine swelling and shrinking values in-situ without disturbing the targeted climatic conditions. The system is applicable for the investigation of natural wood, modified wood, wood composites or other lignocellulosic materials.
... Hence, in the future, the drought-resistant Douglas-fir trees growing in the European forests will potentially produce timber of high wood density. Apart of this, higher values of compression and bending strength were detected in comparison to the native timber, which is in line with the literature (Rijsdijk and Laming 1994;Wagenfür 2000). It is worth mentioning that Douglas-fir growing in the Czech Republic outperformed most of the native European softwood, especially Norway spruce. ...
Important physical and mechanical properties were evaluated for Douglas-fir wood produced in a non-native environment. The specimens were obtained from 15 healthy co-dominant trees growing in three different sites located in the Czech Republic; they were studied for density, shrinkage, compression, and bending strength. The average density of the wood was 562.74 ± 62.47 kg·m-3 at 12% MC. The total volumetric shrinkage was in line with the respective literature, whereas the compression strength and modulus of rupture were found to be higher than the native Douglas-fir wood as well as several European softwoods. The properties of the wood produced in the Czech forests indicate the possibility of producing Douglas-fir timber of high quality.
... Pri hrastovini starostne skupine 100 smo določili povprečne vrednos7 radialnega (q R = 0,208 %/%) in tangencialnega diferencialnega nabreka (q T = 0,372 %/%), kot tudi koeficienta nabrekanja v is7h smereh (h R , h T ; preglednica 4). Vrednos7 kazalnikov dimenzijske stabilnos7 lesa iz skupine 100 so bile primerljive z rezulta7 drugih raziskav recentne hrastovine (Badel et al., 2006;Gorišek, 1992;Kollmann & Cote, 1968;Rijsdijk & Laming, 1994). Večina kazalnikov dimenzijske stabilnos7 (q T , h R , h T ) se je s staranjem hrastovine zmanjševala vse do skupine 400. ...
... Pri hrastovini starostne skupine 100 smo določili povprečne vrednos7 radialnega (q R = 0,208 %/%) in tangencialnega diferencialnega nabreka (q T = 0,372 %/%), kot tudi koeficienta nabrekanja v is7h smereh (h R , h T ; preglednica 4). Vrednos7 kazalnikov dimenzijske stabilnos7 lesa iz skupine 100 so bile primerljive z rezulta7 drugih raziskav recentne hrastovine (Badel et al., 2006;Gorišek, 1992;Kollmann & Cote, 1968;Rijsdijk & Laming, 1994). Večina kazalnikov dimenzijske stabilnos7 (q T , h R , h T ) se je s staranjem hrastovine zmanjševala vse do skupine 400. ...
Raziskali smo fizikalne lastnosti hrastovega lesa (Quercus sp.), pri katerem je od poseka minilo od 4 do 512 let in smo ga razdelili v stoletne starostne skupine 100-600. Mlajši les smo pridobili ob poseku dreves, starejši les pa iz zgodovinskih konstrukcij v Sloveniji. Izbrani les smo najprej dendrokronološko datirali, izdelali normirane vzorce za analize ter določili gostoto, barvo, dimenzijsko stabilnost in sorpcijske lastnosti. Vizualno in v CIELab barvnem prostoru smo ugotovili, da je barva jedrovine s starostjo postala temnejša. Pri starem hrastovem lesu smo ugotovili tudi manjšo higroskopnost in izboljšano dimenzijsko stabilnost, zlasti v tangencialni smeri, ter manjšo prečno krčitveno anizotropijo. Gostota hrastovega lesa se s staranjem ni spremenila, odvisna pa je bila od širine branik (naraščala je z večanjem deleža kasnega lesa). Rezultati nakazujejo, da na dimenzijsko stabilnost in higroskopnost poleg procesov staranja verjetno vpliva tudi mesto vgradnje in klimatska nihanja tekom uporabe lesa.
... Further, due to the cellular nature of wood, it does not swell or shrink equally in all directions. Table 1 shows literature values of differential swelling coefficients for spruce and beech wood [8]. In addition to expansion or contraction, also the mechanical properties of wood change with varying WMC. ...
This research shows an initial investigation in digital modeling of designed active material behaviors for shape-changing and self-forming timber plates based on hygroscopic actuation applicable for environmentally responsive structures and actuators. By explicitly defining orthographic fiber orientation in the layouts and layups within the plate, different curved movements can be designed.
This design space of self-forming movements, combined with the stiffness and high actuation forces in wood, can be applied to large self supporting building components compared to other ‘smart’ materials. This paper presents the process specific digital design and simulation workflow to design such self forming timber plates. Using this tool, the designer can modify upstream material information, which is translated into a FE model to simulate deformation patterns. The designer can fine-tune the input conditions to achieve desired deformed geometries. Case studies are shown for multiple movement patterns based on combinations and variations of single curvature within a standard plate geometry.
The research expands the design space for self-forming plates by allowing methods for adaptations of curvatures. The included FE simulation gives a quick and reliable estimate of the physically achieved deformation patterns given the material uncertainties of wood and the simplification of material properties. The workflow shows the possible design control and simplicity of the system, which can be applied to structural applications such as large-scale actuators or responsive surfaces as well as parts for self-forming or shape-shifting structures.
... By 3D scanning, Gaussian and principal curvatures were quantified ( Fig. 6c and d). For the central parts of the structure, positive Gaussian curvature is visible, indicating synclastic curvature, whereas zero or negative Gaussian curvature (anticlastic curvature) for maple are taken as average from [18,19], values for beech and spruce are taken from studies performed for [8]. b Ratio of elastic modulus E (E L /E R or E L /E T ), calculated from values taken from [20,21]. ...
For the performance of wood as a building material, its dimensional changes in response to alterations of relative humidity are commonly perceived as an adverse effect. Recently, this material inherent property has been proposed to be utilized in a smart way. Employing the bilayer principle, controlled and reversible shape changes in response to changes of relative humidity were demonstrated. Wood naturally inherits a unique combination of material properties specifically suitable for large-scale shape-changing parts. While being environmentally responsive, it offers high mechanical stiffness throughout shape-change, ease of machining and working, and sustainable availability in large sizes and quantities. In this study, we demonstrate design principles for achieving a range of shape changing patterns such as uni- and bi-directional surface curvature of wood and wood-hybrid bilayers with both negative (hyperboloid curvature) and positive Gaussian curvature (spherical curvature). In parallel, we have developed suitable joints to join multiple elements to facilitate upscaling in length and width while maintaining shape-change. The ability to design and control the type and magnitude of curvature for specific sizes, shapes, and aspect ratios open the opportunity for a new class of large-scale weather responsive elements and self-forming building components.
... Los valores de densidad, higroscopicidad y dureza, son algo superiores a los medios de la especie, sin embargo, el coeficiente de contracción volumétrica es menor, por lo que el riesgo de fendas disminuye. El riesgo de deformación, puede considerarse moderado, como indica un coeficiente de anisotropía inferior a 2,2 (1,94) para una anisotropía absoluta del 3,21% (Rijsdijk, Laming, 1994). ...
En este trabajo se estudian las propiedades del Pinus pinaster Ait., procedente de los Montes del Marquesado (Granada), seleccionado por ser una de las coníferas más representativas de las masas forestales y su madera una de las más utilizadas en la industria de carpintería y mueble en la Comunidad andaluza. La caracterización se ha realizado con probetas de pequeñas dimensiones libres de defectos que proporcionan los valores máximos de una determinada propiedad de la madera. Se determinan y analizan seis características morfológicas, quince características físicas y trece propiedades mecánicas. De los resultados de los ensayos de las propiedades mecánicas se desprenden valores próximos a los obtenidos en trabajos similares con esta especie, si bien algo inferiores. Los resultados en resistencia a flexión estática, dinámica e hienda son bajos y su resistencia a compresión axial mediana. En cuanto a las propiedades físicas, resulta una madera semipesada, poco nerviosa y semidura, con unos valores de densidad algo superiores a los medios de la especie. P.C.: Caracterización de maderas, propiedades, pequeñas dimensiones, Pinus pinaster Ait
SUMMARY In this paper we consider the main characteristics of Pinus pinaster Ait, a tree belonging to the most representative conifers in the area of Montes del Marquesado, Granada, which is widely appreciated in the furniture industry in the Community of Andalucia. Analysis have been carried out in small-sized tubes free of faults and able therefore to provide maximum accuracy of wood quality. The following aspects have been evaluated: six morphological characteristics, fifteen physical characteristics and thirteen mechanical properties. The tests concerning mechanical properties have shown results similar to those obtained in analogous tests, although somewhat below in the following aspects. Results concerning resistance to static and dynamic bending, and to cleavage are lower while its resistance to axial pressure is medium. Concerning physical properties, the wood is lightly nervous, medium in weight and hardness, with a density lightly above the mean values of this species.
... According to these sorption isotherms, the corresponding EMCs to which the specimens were conditioned and loaded were 12 M% and 24 M%, respectively. The sorption isotherms were later compared to ad-and desorption isotherms [4] obtained for Norway spruce (origin Central Europe), illustrated with the dashed and dash-dotted lines. Finally, some tests with small specimens conditioned at different relative humidities were performed to verify the isotherms of the used glulam [5]. ...
The hygroscopic behaviour of wood leads to changes in the physical and mechanical properties. The correct estimation of the moisture content is important for the design and life cycle of timber structures. Therefore experimental test series were performed to determine the moisture content distribution over the cross section as a function of loading duration, respecting the glue lines of glulam and block glued cross sections. Alongside, numerical simulations of the moisture diffusion process were set up and validated with the experimental test series. The correlation of the numerical simulation with the reality offers guidance in the design of timber structures.
... In Rijsdijk and Laming (1994) the fiber saturation points and the shrinkage coefficients are given for 145 softwood and hardwood species. In this thesis, as a mean approximation for all wood species, a fiber saturation point of 25% m.c. is used. ...
... A swelling of 4.0% was estimated on the horizontal axis with measurements of distances between rays along the tangential axis of the staves. This value is common for Quercus petraea when toasted in cooperage [32,33]. The vertical axis did not suffer appreciable swelling because the piece of wood was firmly clamped by the device, and the thickness axis was also strongly fixed, exactly as happens in a production barrel stave. ...
This paper explores the use of optical sensors to study the oxygen diffusivity of oak wood staves in wine barrel ageing for four months. 2-D oxygen distribution measurements were performed with planar optodes in combination with a colour RGB camera. The transparency of the optode enables to study the correlation of spatial heterogeneities −due to wood swelling during wetting- in O2 concentration over the wood surface with data on the different anatomical structures involved. For the first time, oxygen dynamics were described with a resolution that permits the identification of the role of wood anatomy on oxygen permeability/diffusivity.
http://www.sciencedirect.com/science/article/pii/S0925400516313041
... The mechanical characteristics of wooden structures can be impressive: The elastic modulus, tensile-, compressive-and break strength, as well as the surface hardness of wood often surpass those of conventional, non-biological materials (Rijsdijk & Laming, 1994). In addition, wooden plants also have the ability to optimize their topology depending on external influences, e.g. ...
Models for predicting physical properties of wood in standing trees are useful for helping to make decisions about tree selection for harvesting and technological use of the material. The objectives of this study were to investigate the variation in physical properties of Douglas fir wood obtained from thinning and to construct a model for predicting wood density on the basis of easy-to-measure properties in thinned trees. Sixteen young Douglas fir trees growing in three stands in Galicia (NW Spain) were felled for the study. Small specimens of defect-free wood were obtained from the trees in order to determine annual growth ring width, density and shrinkage-related properties by standardised testing methods. The sampled wood was homogeneous and light (mean oven-dry density = 429 kg m− 3), and the dimensions were stable in response to changes in moisture content (volumetric shrinkage from saturation to oven-dry state = 12.0%; ratio tangential/radial shrinkage, i.e. anisotropic shrinkage = 1.6). The density of wood in the sampled trees increased with the diameter at breast height and decreased with the height in the stem. The observed significant between-tree and intra-tree variation in wood properties was used to develop a model for predicting oven-dry density, with diameter at breast height and height in the stem as predictor variables (adjusted coefficient of determination = 0.57). The model is useful for estimating wood density along the stem in trees removed during thinning, and the results suggest selecting trees with diameter at breast height over 30 cm when dense wood is needed.
Shisham (Dalbergia sissoo) is considered the most valuable commercial timber in Pakistan due to its better strength, wood working properties and attractive figure. Wood quality is affected by the climate in which wood is grown. Wood is a natural material and many continually evolving factors, which may contribute and affects the individual characteristics of wood, such as MoE, MoR, hardness and other properties. It is important to have the knowledge about the physical and strength properties of the Shisham (Dalbergia sissoo) wood to identify the particular forest type where it can grow better for production of valuable timber resources and rational utilization. In this study Shisham (Dalbergia sissoo) wood samples were collected from three different forest types of Khyber Pakhtunkhwa i.e., SubTropical Broad Leaved, Tropical Thorn and Tropical Dry Deciduous Forests and tested for Physico-mechanical properties. Random sites were selected from each forest types i.e. Dera Ismail Khan from Tropical Thorn Forest, Kohat from Tropical Dry Analysis of Variance MANOVA was run by R-Package and Homogeneous subsets on SPSS to determine statistically significant effects of different sites on strength properties of Shisham (Dalbergia sissoo) wood grown in three different forest types and to assess correlation between density and strength properties. Post hoc multiple pair-wise comparisons were performed using Games Howell and Tukey HSD test p < 0.05. Based upon the results of the present study, it has been revealed that the wood grown in Dera Ismail Khan Site has relatively high value of density and superior in strength properties than Kohat, Swabi and Peshawar sites. It is recommended that the Shisham (Dalbergia sissoo) wood from Tropical Thorn Forest has better production and utilization potential in wood based industries particularly furniture industries of Pakistan with valuable hardwood timber. Whereas, the stiffness property (MoE) is of prime concern, Shisham (Dalbergia sissoo) wood from Tropical Dry Deciduous Forest i.e. Kohat site was the best choice amongst the studied sites. Therefore, wood density is recommended as a wood quality indicator for assessing the preliminary quality and other wood properties in wood based industries and domestic use of wood.
Blighia sapida, a Lesser-Used Species is being processed into sawn timber to meet the demand for wood. The knowledge of its wood quality would enhance its effective utilization. However, there is little information known on the physical properties of this species that could enhance its acceptability and optimum utilization. This, therefore, necessitate the need to investigate the physical properties of this wood species. Three standing trees of B. sapida were purposively felled for this study. Billets of 500 mm were obtained from the wood disc at the base, middle, and top of the tree. Each wood disc was partitioned into three; innerwood, middlewood, and outerwood following specified international standards for the physical properties test (wood colour, proportion of sapwood and heartwood, bark thickness, density, moisture content, and volumetric shrinkage). B. sapida wood density with a mean value of 709.78±8.88 kg/m3, ranged from (571.59±13.45 to 854.81±7.08 kg/m3. Moisture content percentage of average value 70.62±1.23%, ranged from 53.84±1.40 to 89.00±2.75%. Volumetric shrinkage of average value 15.24±0.25%, range from 13.38±0.66 to 16.89±0.83%. The range of B. sapida wood density value of the study falls within the range that could be categorized as medium density wood of medium construction strength properties. The 1:1.5% tangential–radial shrinkage observed in this study was low, an indicator of a low risk of deformation while seasoning the wood, as the ratios of tangential-radial shrinkage that is high are those over 2.2%.
As countries advance in greenhouse gas accounting for climate change
mitigation, consistent estimates of aboveground net biomass change are
needed. Countries with limited forest monitoring capabilities in the tropics and sub‐
tropics rely on IPCC 2006 default rates, which are values per ecological zone,
per continent. Similarly, research into forest biomass change at a large scale also makes
use of these rates. IPCC 2006 default rates come from a handful of studies, provide
no uncertainty indications and do not distinguish between older secondary forests
and old‐growth forests. Since the 2019 Refinement to the 2006 IPCC Guidelines
for National Greenhouse Gas Inventories was done, it was incorporated some keys for improving the GHG calculations in the forest land.
La conception et la vérification du dimensionnement des structures en bois, pour une utilisation en Génie Civil, est régie par la norme Européenne Eurocode 5. Elle permet de dimensionner tout élément de structure en fonction du chargement qui lui est appliqué et d’hypothèses relatives à son environnement. Coordonnée particulièrement par la filière bois des pays Nordiques, cette norme est basée sur l’emploi exclusif de résineux. Or, la France détient la plus grande forêt de feuillus d’Europe. Ces essences ont leur place dans les structures bois d’aujourd’hui en apportant, par exemple, des propriétés de durabilité naturelle. Malheureusement, ces essences ne sont pas aujourd’hui considérées dans les règles de dimensionnement.Le projet EFEUR5, financé par l’agence nationale de la recherche, a pour objectif de répondre à cette problématique en effectuant des travaux similaires à ceux déjà réalisés pour les résineux. Ainsi, les travaux présentés ont pour objectifs de comprendre et de modéliser le comportement mécanique différé des essences de feuillus français que sont le chêne, le hêtre et le peuplier. A ces trois essences, est rajouté le douglas comme essence de référence des résineux.Nous commençons l’étude par l’analyse microscopique de la structure anatomique des essences étudiées. Cette analyse a pour objectif de mettre en avant les différences entre ces quatre essences. Le comportement mécanique différé du bois étant sensible à l’humidité de celui-ci, nous devons dans un premier temps déterminer l’évolution de l’humidité dans la section d’un élément de structure. Pour cela, il est présenté dans le second chapitre un protocole expérimental innovant de détermination des propriétés de diffusion d’une éprouvette située en extérieur. L’identification des propriétés de diffusion effectuée, nous proposons une étude de sensibilité des écarts de comportement hydrique sur un élément de structure.Le comportement mécanique long terme est ensuite étudié par une approche couplée entre expérimentation et modélisation. Différents comportements mécaniques dépendant du temps et de l’humidité sont pris en compte et hiérarchisés. L’implémentation, dans un logiciel aux éléments finis, de l’évolution du champ hydrique 3D au sein d’un élément de structure, ainsi que des différents phénomènes physiques mis en jeu lors du fluage sont discutés. Par la suite, la conception de deux bancs de flexion quatre points à l’échelle métrique des poutres de feuillus et de douglas est détaillée. Les mesures réalisées sur plus d’une année permettent dans un premier temps d’identifier les principaux comportements. Dans un second temps, ces données permettent de déterminer les propriétés viscoélastiques hygro activées par analyse inverse. Ainsi une comparaison des propriétés viscoélastiques entre ces quatre essences est présentée.Enfin, dans la dernière partie, les modèles développés et validés sont mis en forme pour une approche technologique. De nouveaux abaques d’équilibre d’humidité interne sont proposés essence par essence. Une méthodologie de détermination du coefficient kdef est proposée, et permet, par une relation très simple, d’affiner sa détermination en fonction de l’environnement réel, de la section, et de l’humidité initiale.
The laurel (Laurus nobilis L.) is a common species in southern Europe, but the properties of its wood are not well described in the literature and from that perspective any novel information is valuable. Because of that, a group of laurels was felled for the analysis of wood properties on small defect-free specimens (17 trees and 1250 valid specimens). The sampled wood was moderately heavy and unstable. The following mean values were obtained (density at 12% moisture content 699 kg m⁻³; basic density 566 kg m⁻³; total volumetric shrinkage 18.0%; volumetric shrinkage coefficient 0.59%). Highly significant inter-tree and intra-tree variation was observed for most of the properties considered. The inter-tree variation was attributed to tree dimensions, being remarkable that volumetric, radial and tangential shrinkage coefficients were significantly related to breast height diameter and slenderness. The trends of these variables suggest that in trees older than those used in the study (24–41 years old) the dimensional stability would increase. As regards the inter-tree variation, a low but highly significant decrease was found for density at highest positions in the tree. Volumetric and linear shrinkage diminish very significantly along the stem. Due to the uniformity of density and the increment of wood dimensional stability along the trunk, the harvesting of the full stem is advisable.
To quantify the impact of forest management practices and tree growth rate on the potential uses of Douglas-fir wood, nine physico-mechanical properties were studied on more than 1250 standardized clear specimens. These were collected from trees cut in 11 even-aged stands (six trees per stand) located in Wallonia (southern Belgium). Stands were 40 to 69 years old, and mean tree girth was ca. 150 cm. Mean ring width of the 66 trees ranged from 3 to more than 7 mm. Statistical analysis showed significant but weak effects of ring width on the studied properties. Considered jointly, mean ring width and cambial age of the test specimens only explained 28% to 40% of the variability of their properties. Also, when ring width increases, these properties display higher decreases in juvenile wood than in mature wood. From a technological standpoint, maintaining mean ring width under 4 mm in juvenile wood and 6 mm in mature wood should accommodate all potential uses of Douglas-fir wood. However, considering that density appeared to be the main driver of wood properties, our results and the literature corroborate the importance of genetic selection as a complement to silvicultural measures to improve or guarantee the technological properties of Douglas-fir wood.
Like other lignocellulosic materials, wood has the ability to exchange moisture with its surrounding environment. This means that wood can adsorb or release moisture until it is in equilibrium with its surrounding environment. Changes of the moisture content causes swelling or shrinking of wood which is different in the longitudinal, radial and tangential direction. This shrinking and swelling can result in warping, checking and/or splitting of wood, restricting its use in service conditions. In order to reduce the water uptake of wood and wood composites, methods have been developed improving its dimensional stability. In this chapter several commercial methods which have been developed in the last decades are discussed.
Adequate information is sparse for many tropical timbers on their engineering applications, which make their international promotion difficult. The physical and mechanical properties of Klainedoxa gabonensis Pierre ex Engl. (a lesser-utilized species) and Entandrophragma cylindricum were compared. K. gabonensis contained more moisture with greater density at 12 % moisture content than E. cylindricum and had a tangential–radial ratio for swelling and shrinkage of 1.31–1.38 and 1.58–1.63, respectively, within acceptable thresholds for engineering/structural timbers. For K. gabonensis, shear parallel to grain was 32.2 ± 0.4–33.5 ± 1 N mm⁻²; compressive parallel to grain, 80.7 ± 1.4–90.6 ± 1 N mm⁻²; modulus of rupture, 204 ± 4.0–214 ± 4.0 N mm⁻² and modulus of elasticity, 28,932 ± 664–29,493 ± 822 N mm⁻². These properties were superior to those of E. cylindricum [(15.5 ± 0.9)–(15.6 ± 0.6), (56.4 ± 4.5)–(63.6 ± 1.2), (99.4 ± 4.7)–(121.3 ± 10.6), and (9987.4 ± 207)–(10,051 ± 258) N mm⁻², respectively] and compared well with those of several traditional timbers for construction and furniture production. Its use would contribute to minimize pressure on the primary timbers in the forests and widen the raw material base for wooden products. © 2016 Northeast Forestry University and Springer-Verlag Berlin Heidelberg
Savannas and adjacent vegetation types like gallery forests are highly valuable ecosystems contributing to several ecosystem services including carbon budgeting. Financial mechanisms such as REDD+ (Reduced Emissions from Deforestation and Forest Degradation) can provide an opportunity for developing countries to alleviate poverty through conservation of its forestry resources. However, for availing such opportunities carbon stock assessments are essential. Therefore, a research study for this purpose was conducted at two protected areas (Nazinga Game Ranch and Bontioli Nature Reserve) in Burkina Faso. Similarly, analysis of various vegetation parameters was also conducted to understand the overall vegetation structure of these two protected areas. For estimating above ground biomass, existing allometric equations for dry tropical woody vegetation types were used. Compositional structure was described by applying tree species and family importance indices. The results show that both sites collectively contain a mean carbon stock of 3.41 ± 4.98 Mg·C·ha⁻¹. Among different savanna vegetation types, gallery forests recorded the highest mean carbon stock of 9.38 ± 6.90 Mg·C·ha⁻¹. This study was an attempt at addressing the knowledge gap particularly on carbon stocks of protected savannas—it can serve as a baseline for carbon stocks for future initiatives such as REDD+ within these areas.
Class groups for made on the basis of physico-mechanical values, and the distribution of grown in Turkeytree species have been made in these classes. In classification, air dry (12-15%) density, shrinkage, bending strength, modulus of elasticity in bending, impact bending, compression, tensile, cleavage, shearing strength and hardness values were used.
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