Douglas-fir(Pseudotsuga menziesii(Mirb.)Franco),one of the most commercially important tree species in western North America and one of the most valuable timber trees worldwide,was introduced to Europe in 1827.It beca...Douglas-fir(Pseudotsuga menziesii(Mirb.)Franco),one of the most commercially important tree species in western North America and one of the most valuable timber trees worldwide,was introduced to Europe in 1827.It became a major species for aff orestation in Western Europe after WWII,currently grows in 35 countries on over 0.83 million ha and is one of the most widespread nonnative tree species across the continent.A lower sensitivity to drought makes Douglas-fi r a potential alternative to the more drought-sensitive Norway spruce so its importance in Europe is expected to increase in the future.It is one of the fastest growing conifer species cultivated in Europe,with the largest reported dimensions of 2.3 m in diameter and 67.5 m in height.Pure stands have high productivity(up to 20 m 3 ha−1 a−1)and production(over 1000 m 3 ha−1).The species is generally regenerated by planting(initial stocking density from less than 1000 seedlings ha−1 to more than 4000 ha−1),using seedlings of European provenance derived from seed orchards or certifi ed seed stands.As the range of end-uses of its wood is very wide,the rotation period of Douglas-fi r is highly variable and ranges between 40 and 120 years.When the production of large-sized,knotfree timber is targeted,thinnings are always coupled with pruning up to 6 m.There is an increasing interest in growing Douglas-fi r in mixtures and managing stands through close-to-nature silviculture,but the species’intermediate shade tolerance means that it is best managed through group selection or shelterwood systems.展开更多
This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers wer...This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers were considered to evaluate the tensile strengths and ductility performances of the STS joints.The screws with 6 mm diameter and the innovative steel-tubes with 18 mm diameter were adopted as connecting fasteners.The experimental results were discussed in terms of yielding and ultimate strengths,slip stiffness,and ductility factors.The ductility classification and failure mechanisms of each group of specimens were analyzed.It was demonstrated that the STS joint with large diameter steel-tubes showed acceptable ductility,which was close to the ductility of the STS joint with small diameter screws,thanks to the hollow structure of the steel-tube.The theoretical strengths of various failure modes for the joints with small diameter screws or large diameter steel-tubes were calculated and compared with the experimental results.The ductile performance of the STS joint was discussed by comparing the theoretical strengths of various failure modes.The effective number of the STS joint with multifasteners was also analyzed by considering the failure mechanisms in aspects of tensile strength and slip stiffness.展开更多
Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an i...Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.展开更多
The comprehensive utilization of wood is the main goal of log cutting,but knot defects increase the diffi-culty of rationally optimizing cutting.Due to the lack of real shape data of knot defects in logs,it is diffi c...The comprehensive utilization of wood is the main goal of log cutting,but knot defects increase the diffi-culty of rationally optimizing cutting.Due to the lack of real shape data of knot defects in logs,it is diffi cult for detection methods to establish a correlation between signal and defect morphology.An image-processing method is proposed for knot inversion based on distance regularized level set segmentation(DRLSE)and spatial vertex clustering,and with the inversion of the defects existing relative board position in the log,an inversion model of the knot defect is established.First,the defect edges of the top and bottom images of the boards are extracted by DRLSE and ellipse fi tting,and the major axes of the ellipses made coplanar by angle correction;second,the coordinate points of the top and bottom ellipse edges are extracted to form a spatial straight line;third,to solve the intersection dispersion of spatial straight lines and the major axis plane,K-medoids clustering is used to locate the vertex.Finally,with the vertex and the large ellipse,a 3D cone model is constructed which can be used to invert the shape of knots in the board.The experiment was conducted on ten defective larch boards,and the experimental results showed that this method can accurately invert the shapes of defects in solid wood boards with the advantages of low cost and easy operation.展开更多
Heat-treated wood has good dimensional stability,durability,and color,but its susceptibility to fungal growth affects its commercial value.In this study,lumber harvested from mature Masson’s pine(Pinus massoniana Lam...Heat-treated wood has good dimensional stability,durability,and color,but its susceptibility to fungal growth affects its commercial value.In this study,lumber harvested from mature Masson’s pine(Pinus massoniana Lamb.)was vacuum impregnated with a basic copper salt solution(copper hydroxide,diethanolamine,and polyethylene glycol 200)prior to heat-treatment at 220℃ for 3 h.Antifungal properties,surface chemistry,crystal structure and sugar contents were tested,compared with heat treatment alone.The results showed that the samples treated by heating without copper salt treatment showed poor suppression of fungal growth,the copperimpregnated heat-treated wood suppressed(100%)the growth of Botryodiplodia theobromae Pat.,Aspergillus niger V.Tiegh.,Penicillium citrinum Thom,and Trichoderma viride Pers.The combined results of X-ray photoelectron spectroscopy,X-ray diffraction and sugars analysis suggested that fungal inhibition by the heat-treated copper-bearing Masson’s pine was mainly due to the reduction of the metal salt by PEG200 at high temperature to generate copper nanoparticles.In addition,the reduced sugar content of the treated timber,and hence the nutrient substrate for spoilage microbes,reduced in the presence of the metal salts at high-temperature.This study has demonstrated an effective method of increasing low-grade wood’s utility and commercial value.展开更多
The depth adjustment factor for bending strength stated in Eurocode 5(EC5)is only applicable to timbers having a characteristic density below 700 kg/m^(3).However,most Malaysian timbers are hardwood,some with a charac...The depth adjustment factor for bending strength stated in Eurocode 5(EC5)is only applicable to timbers having a characteristic density below 700 kg/m^(3).However,most Malaysian timbers are hardwood,some with a characteristic density reaching above 700 kg/m^(3).Therefore,the objective of this study was to examine whether the depth adjustment factor stipulated in EC5 is valid for Malaysian hardwood timbers.Six timber species were selected for this study,namely Kapur(Dryobalanops C.F.Gaertn.),Kempas(Koompassia Maingay ex Benth.),Keruing(Dipterocarpus C.F.Gaertn.),Light red meranti(Shorea Roxb.ex C.F.Gaertn.),Geronggang(Cratoxylum Blume)and Balau(Shorea Roxb.ex C.F.Gaertn.).The determination of bending strength and characteristic density was conducted according to BS EN 408:2010 and BS EN 384:2016,respectively.A graph for mean bending strength vs.(150/h)was plotted for each timber species.The power function was selected to analyze the relationship between the two variables.The power of the regression equations varied depending on the characteristic density of the timber species.For species with a characteristic density below 700 kg/m^(3),such as Kapur,Keruing,and Light red meranti,the power was between 0.16 to 0.17.In contrast,for species having a characteristic density above 700 kg/m^(3),namely Kempas and Balau,the power was higher at 0.23 and 0.24,respectively.Geronggang was an exception to this pattern.These values are close to the depth adjustment factor given in EC5,which is 0.2.Based on the results,it can be suggested that the adjustment factor of 0.2 is also applicable to Malaysian hardwood timbers with a characteristic density above 700 kg/m^(3).展开更多
One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. ...One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. Despite many researches on wood’s mechanical and physical properties, only a few are geared toward the structural application of wood. The present work investigated the mechanical properties of five timber species;Gmelina arborea, Tectona grandis (Teak), Terminalia superba (Afara), Ayin (Anogeissus leiocarpus), and Acacia (Robinia pseudoacacia), to determine their suitability for constructing long-span roof trusses. These are available in the South Western part of Nigeria. Their mechanical properties;bending strength, compressive strength, shear strength, tensile strength, Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and density, were determined in the laboratory. The results obtained showed that all the timber types, except Terminalia superba (Afara), have higher values of mechanical properties than the values that are obtainable for classes of strength D30 to class D70 in the British Code of Practice. It means these species are of higher quality than the stipulated strength classes in the British code. The results also show that the order of relevance of the species for structural design (or work) is Acacia (Robinia pseudoacacia), Ayin (Anogeissus leiocarpus), Gmelina Arborea, and Tectona grandis (Teak). Terminalia superba (Afara) is not recommended for structural works.展开更多
The twenty-first century is one of the most complex in the history of humanity,mainly due to the ecological crisis it is going through.The construction sector generates about 40%of CO2 emissions into the environment;t...The twenty-first century is one of the most complex in the history of humanity,mainly due to the ecological crisis it is going through.The construction sector generates about 40%of CO2 emissions into the environment;the foregoing should motivate this sector to seek new alternatives to develop new building practices.Taking these current needs into account,this document classifies and presents a multidisciplinary solution that integrates biology,engineering and architecture to develop a new and innovative lightweight timber structure;it divides with a main structure made of timber and an innovative joint system made of bio-polymers connecting all the panels.Through the study of diatoms,it was able to analyze the bio-morphology of the structure,joints and in particular the geometry since they were the inspiration for the design of this structure that presents an innovative and novel design of structural optimization.Through parametric design and digital fabrication,it was able to create a complex geometry that obtains excellent structural behavior.This research discusses and explores how materials,geometry led to the optimization of a structure and how new structures can arise,thanks to biology new solutions can be obtained that are completely sustainable,being a clear example of how to combat the effects of the climate change and in a precise way it highlights the advantages of the bio-design in the architectural design.展开更多
This project deals with architecture and engineering involved in the process of architectural design.Based on native irregular components,it aims at developing an innovative approach in the conception and rationalizat...This project deals with architecture and engineering involved in the process of architectural design.Based on native irregular components,it aims at developing an innovative approach in the conception and rationalization of non-standard structures.Contemporary architecture and its non-classical structures require the design of customized pieces.This process which is highly energy and resources consumptive does not always take into account the inherent material properties.This project develops a way of optimizing,in architectural structures,the use of native wood pieces that are not industrially transformed(e.g.boughs)or of reused pieces of carpentry.As a consequence,the ecological footprint of the structures would be reduced.展开更多
Two analytical procedures (Crank's method and Dincer's method) for porous solid materials were reevaluated and used to determine moisture diffusion coefficients and moisture transfer coefficients for larch lumber ...Two analytical procedures (Crank's method and Dincer's method) for porous solid materials were reevaluated and used to determine moisture diffusion coefficients and moisture transfer coefficients for larch lumber subjected to drying. A diffusion-like equation was used to describe drying process data. The lumber was idealized in the modeling as infinite plates. The moisture transport process inside the board was assumed to be one-dimensional. The macroscopic drying kinetics curves of larch timber at particular conditions were determined experimentally. Based on these data, calculation for both the moisture diffusion coefficients and moisture transfer coefficients by the Dincer's analytical procedure were made. The dynamic moisture diffusion coefficients by the traditional Crank's method were calculated. In general, diffusion coefficients calculated by the Dincer's method were all higher than those by Crank's method. These results could be due to the differences between two analytical methods and also different characteristics between solid moisture diffusion process and heat transfer process. Therefore the analysis and solution procedures of moisture diffusion differential equations need to be adapted in the future. With drying temperature's increasing moisture diffusion coefficient (D) and moisture transfer coefficient (k) increases accordingly. Also the relationships between diffusion coefficients and temperature as well as material moisture contents were analyzed by using Arrhenius equation and bound water transport theory.展开更多
Objective:To document ethnobotanical informations of useful woody plant species in the region of Kotli,Azad Kashmir.Methods:An ethnobotanical survey was conducted in Kotli.Data were collected by interview and semi str...Objective:To document ethnobotanical informations of useful woody plant species in the region of Kotli,Azad Kashmir.Methods:An ethnobotanical survey was conducted in Kotli.Data were collected by interview and semi structured questionnaire from selected local informants and traditional practitioners as well as by field assessment.Results:The present study documented the etnobotanical uses of 33 woody plant species.Most of the species have been used for dual purpose.Only 5 species are used for one purpose.Study revealed all species have medicinal value,among which 21 were used as fuel wood species,16 as fodder species,4 as timber wood species,12 as edible fruit species,6 as fence or hedge plant,7 as ornamental species and 12 species had other uses.Conclusions:Medicinal plants are still widely used for health care by locals of Kotli.Some species of woodlands seem to be vulnerable to overcollection and deforestation.As the young generation is diverted toward allelopathic medicines,ethnobotanical knowledges of important medicinal plants are restricted to the old people only.It is suggested to close the forest of district Kotli for next two to three decades for the conservation of plant biodiversity.展开更多
In the megadiverse forests of Southeast Asia, hundreds of timber species are economically important but the population genetics of only a few taxa are known. Cross-specific amplification of microsatellite loci among c...In the megadiverse forests of Southeast Asia, hundreds of timber species are economically important but the population genetics of only a few taxa are known. Cross-specific amplification of microsatellite loci among closely related taxa could enhance our ability to study and manage previously unstudied species. We successfully utilized STMS markers in Shorea platyclados, originally developed for Shorea curtisii. The six primer pairs we tried successfully produced PCR products of expected sizes. The number of alleles observed ranged from 10 to 14 and an average of 12 alleles were detected per locus. A high expected and observed heterozygosity was observed and it ranges from 0.718 to 0.827 among all populations across all six loci tested. Microsatellite DNA markers are highly polymorphic, co-dominant, reproducible, and amenable to high throughput genetic analyses. Overall, the cross- specific amplification of microsatellite loci appears to be complicated by numerous factors. While the approach may be effective for local management and conservation ofpoorly known species, the results must be carefully interpreted.展开更多
This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber vol...This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber volume of 440 open-pollinated half-sib progeny families were investigated in 14 progeny trials in different years and production regions.An evaluation of the genetic variation of all half-sib families was carried out during the sustainable rapid growth period and individual volumes were characterized as a major index.ANOVA analysis showed that there was considerable variance in the growth traits of most families in different years and on different sites.The variations caused by temporal and spatial changes of the mating system required three selection methods for analysis.The results show that there were differences among the heritabilities of different growth traits by different halfsib progenies.Average heritability values of height,DBH and volume were 0.33,0.34 and 0.36,respectively.Fortyfive superior families were selected in every progeny test,12 were selected in progeny trials by different years and five in different habitat progeny trials.Three superior families(Gui GC553A,Gui GC414A and Gui GC431A)were selected,although in different years and production regions.The genetic gains of timber volume of these selected r families ranged from 1.20 to 47.00%,which could provide a foundation for superior wood property selection and serve as material for seed improvement and extension in surrounding areas.展开更多
This paper reports on the effect of various micropropagation factors of Gmelina arborea Roxb. through multiple shoot induction. Factors like the source and age of explants, plant growth regulators (PGRs), media comp...This paper reports on the effect of various micropropagation factors of Gmelina arborea Roxb. through multiple shoot induction. Factors like the source and age of explants, plant growth regulators (PGRs), media composition, and carbon source affected multiple shoot-ing in the present study. Among all the explants used, only shoot tips derived from one, two, and three week old seedlings could form multiple shoots. Besides, the formation of multiple shoots depended on the con-centration and combination of PGRs. Among all the PGRs, BAP (6-benzylaminopurine) alone gave the highest regeneration efficiency. Simi-larly, IBA (Indole-3-butyric acid) was the most efficient PGR in inducing root formation in the microshoots. Media composition and carbon source also affected the regeneration efficiency. MS (Murashige and Skoog medium) proved to be the best media for regeneration followed by B5, SH (Schenk and Hilderbrandt medium) and WPM (Woody plant medium) in that order. Similarly, among sugars, only sucrose and glucose sup-ported induction of microshoots. Based on this study we recommend the use of glucose in place of sucrose in MS medium for maximum regenera-tion efficiency.展开更多
We present management tools for growing four valuable broadleaved tree species, indigenous to subtropi.cal southern China. Crown diameter (CD) of the species studied can be predicted very well by using a model that ...We present management tools for growing four valuable broadleaved tree species, indigenous to subtropi.cal southern China. Crown diameter (CD) of the species studied can be predicted very well by using a model that is so e y a near funct on of d ameter at breast he ght (DBH). The add t on of tree age (AGE) and yield class (YC) to this-nodel did not significantly improve its predictive capacity. We used species-specific crown diameter models to calcu- ate the amount of growing space and subsequently stand density that each species needs to achieve desired stem "adial growth rates. Furthermore we used this information to calculate a "distance factor", a rule of thumb that roughly ~stimates the distance between two neighboring trees needed to achieve a desired future target diameter. These tools 'acilitate the planning of thinning regimes by using crown diameter models combined with annual radial growth rates to ;alculate the number of crop trees per hectare required to reach a desired target stem diameter.展开更多
On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion s...On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the 'strong column, weak beam' design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.展开更多
Eucalyptus is a major fast-grown species in South China,which has the potential for producing structural wood products such as cross-laminated timber(CLT).Aspect ratio(board width vs.board thickness)of eucalyptus lumb...Eucalyptus is a major fast-grown species in South China,which has the potential for producing structural wood products such as cross-laminated timber(CLT).Aspect ratio(board width vs.board thickness)of eucalyptus lumbers is small due to the small diameter of fast-grown eucalyptus wood.To evaluate its rolling shear modulus and strength for potential CLT applications,three-layer hybrid CLT shear block specimens with different aspect ratios(2,4,6),were tested by planar shear test method.Digital image correlation(DIC)was employed to measure the rolling shear strain distribution and development during the planar shear tests.The mean values of rolling shear modulus and strength of eucalyptus lamination were 260.3%and 88.2%higher than those of SPF(Spruce-pine-fir)lamination with the same aspect ratio of 4,respectively.The rolling shear properties of eucalyptus laminations increased as the aspect ratio increased.Aspect ratio had a significant influence on rolling shear modulus compared to rolling shear strength.The high shear strain regions were primarily found around the gaps between segments of cross layer.The quantity of high shear strain regions increased as the aspect ratio of lamination decreased.Other high shear strain regions also occurred around the pith and along the glue line.The sudden failure of specimen occurred in the high strain region.In conclusion,the rolling shear strength and modulus of fast-grown eucalyptus laminations exceed the respective characteristic values for softwoods in the current standard by roughly factors of 3 and 8,indicating great potential for fast-grown eucalyptus wood cross-layers in CLT.展开更多
Tenon-mortise joint is widely used in traditional timber structures around the world.This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and C...Tenon-mortise joint is widely used in traditional timber structures around the world.This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and CNC technology instead of traditional material and manual work.30 full-scale tenonmortise joints were manufactured and tested under monotonic loading,and the effects of dimension,shape,processing error and adhesive were evaluated.It was found that the round rectangular shaped tenon-mortise joints were comparable with traditional joints in terms of structural performance,but were time and labor saving.The variability of the proposed tenon-mortise joints was lower,which would benefit the design value.Applying adhesive between tenon and mortise increased the average stiffness by 4.3 times and average moment capacity by 27.4%,respectively.The gaps between wood members had little effect on the capacity and stiffness in monotonic bending but may influence the energy dissipation ability in cyclic bending.This study showed the feasibility of combining the traditional joinery method with modern wood products and manufacturing technology,which may promote the application of tenon-mortise joints in modern timber structures.展开更多
文摘Douglas-fir(Pseudotsuga menziesii(Mirb.)Franco),one of the most commercially important tree species in western North America and one of the most valuable timber trees worldwide,was introduced to Europe in 1827.It became a major species for aff orestation in Western Europe after WWII,currently grows in 35 countries on over 0.83 million ha and is one of the most widespread nonnative tree species across the continent.A lower sensitivity to drought makes Douglas-fi r a potential alternative to the more drought-sensitive Norway spruce so its importance in Europe is expected to increase in the future.It is one of the fastest growing conifer species cultivated in Europe,with the largest reported dimensions of 2.3 m in diameter and 67.5 m in height.Pure stands have high productivity(up to 20 m 3 ha−1 a−1)and production(over 1000 m 3 ha−1).The species is generally regenerated by planting(initial stocking density from less than 1000 seedlings ha−1 to more than 4000 ha−1),using seedlings of European provenance derived from seed orchards or certifi ed seed stands.As the range of end-uses of its wood is very wide,the rotation period of Douglas-fi r is highly variable and ranges between 40 and 120 years.When the production of large-sized,knotfree timber is targeted,thinnings are always coupled with pruning up to 6 m.There is an increasing interest in growing Douglas-fi r in mixtures and managing stands through close-to-nature silviculture,but the species’intermediate shade tolerance means that it is best managed through group selection or shelterwood systems.
基金supported by National Natural Science Foundation of China(Grant Nos.52208253,51878344)Postdoctoral Foundation of Jiangsu Province(Grant No.2021K128B)Jiangsu Funding Program for Excellent Postdoctoral Talent,which are highly appreciated.
文摘This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers were considered to evaluate the tensile strengths and ductility performances of the STS joints.The screws with 6 mm diameter and the innovative steel-tubes with 18 mm diameter were adopted as connecting fasteners.The experimental results were discussed in terms of yielding and ultimate strengths,slip stiffness,and ductility factors.The ductility classification and failure mechanisms of each group of specimens were analyzed.It was demonstrated that the STS joint with large diameter steel-tubes showed acceptable ductility,which was close to the ductility of the STS joint with small diameter screws,thanks to the hollow structure of the steel-tube.The theoretical strengths of various failure modes for the joints with small diameter screws or large diameter steel-tubes were calculated and compared with the experimental results.The ductile performance of the STS joint was discussed by comparing the theoretical strengths of various failure modes.The effective number of the STS joint with multifasteners was also analyzed by considering the failure mechanisms in aspects of tensile strength and slip stiffness.
文摘Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.
基金supported fi nancially by the China State Forestry Administration“948”projects(2015-4-52),and Hei-longjiang Natural Science Foundation(C2017005).
文摘The comprehensive utilization of wood is the main goal of log cutting,but knot defects increase the diffi-culty of rationally optimizing cutting.Due to the lack of real shape data of knot defects in logs,it is diffi cult for detection methods to establish a correlation between signal and defect morphology.An image-processing method is proposed for knot inversion based on distance regularized level set segmentation(DRLSE)and spatial vertex clustering,and with the inversion of the defects existing relative board position in the log,an inversion model of the knot defect is established.First,the defect edges of the top and bottom images of the boards are extracted by DRLSE and ellipse fi tting,and the major axes of the ellipses made coplanar by angle correction;second,the coordinate points of the top and bottom ellipse edges are extracted to form a spatial straight line;third,to solve the intersection dispersion of spatial straight lines and the major axis plane,K-medoids clustering is used to locate the vertex.Finally,with the vertex and the large ellipse,a 3D cone model is constructed which can be used to invert the shape of knots in the board.The experiment was conducted on ten defective larch boards,and the experimental results showed that this method can accurately invert the shapes of defects in solid wood boards with the advantages of low cost and easy operation.
基金This research was sponsored by the Guangdong Forestry Science and Technology Innovation Project“Research on the Thermal Modification of Eucalyptus and Spingbract Chinkapin Wood and the Key Technologies of Their Wood Flooring Preparation”(No.2018KJCX006).
文摘Heat-treated wood has good dimensional stability,durability,and color,but its susceptibility to fungal growth affects its commercial value.In this study,lumber harvested from mature Masson’s pine(Pinus massoniana Lamb.)was vacuum impregnated with a basic copper salt solution(copper hydroxide,diethanolamine,and polyethylene glycol 200)prior to heat-treatment at 220℃ for 3 h.Antifungal properties,surface chemistry,crystal structure and sugar contents were tested,compared with heat treatment alone.The results showed that the samples treated by heating without copper salt treatment showed poor suppression of fungal growth,the copperimpregnated heat-treated wood suppressed(100%)the growth of Botryodiplodia theobromae Pat.,Aspergillus niger V.Tiegh.,Penicillium citrinum Thom,and Trichoderma viride Pers.The combined results of X-ray photoelectron spectroscopy,X-ray diffraction and sugars analysis suggested that fungal inhibition by the heat-treated copper-bearing Masson’s pine was mainly due to the reduction of the metal salt by PEG200 at high temperature to generate copper nanoparticles.In addition,the reduced sugar content of the treated timber,and hence the nutrient substrate for spoilage microbes,reduced in the presence of the metal salts at high-temperature.This study has demonstrated an effective method of increasing low-grade wood’s utility and commercial value.
基金funded by Geran Penyelidikan Khas(GPK),(600-RMC/GPK 5/3(071/2020)).
文摘The depth adjustment factor for bending strength stated in Eurocode 5(EC5)is only applicable to timbers having a characteristic density below 700 kg/m^(3).However,most Malaysian timbers are hardwood,some with a characteristic density reaching above 700 kg/m^(3).Therefore,the objective of this study was to examine whether the depth adjustment factor stipulated in EC5 is valid for Malaysian hardwood timbers.Six timber species were selected for this study,namely Kapur(Dryobalanops C.F.Gaertn.),Kempas(Koompassia Maingay ex Benth.),Keruing(Dipterocarpus C.F.Gaertn.),Light red meranti(Shorea Roxb.ex C.F.Gaertn.),Geronggang(Cratoxylum Blume)and Balau(Shorea Roxb.ex C.F.Gaertn.).The determination of bending strength and characteristic density was conducted according to BS EN 408:2010 and BS EN 384:2016,respectively.A graph for mean bending strength vs.(150/h)was plotted for each timber species.The power function was selected to analyze the relationship between the two variables.The power of the regression equations varied depending on the characteristic density of the timber species.For species with a characteristic density below 700 kg/m^(3),such as Kapur,Keruing,and Light red meranti,the power was between 0.16 to 0.17.In contrast,for species having a characteristic density above 700 kg/m^(3),namely Kempas and Balau,the power was higher at 0.23 and 0.24,respectively.Geronggang was an exception to this pattern.These values are close to the depth adjustment factor given in EC5,which is 0.2.Based on the results,it can be suggested that the adjustment factor of 0.2 is also applicable to Malaysian hardwood timbers with a characteristic density above 700 kg/m^(3).
文摘One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. Despite many researches on wood’s mechanical and physical properties, only a few are geared toward the structural application of wood. The present work investigated the mechanical properties of five timber species;Gmelina arborea, Tectona grandis (Teak), Terminalia superba (Afara), Ayin (Anogeissus leiocarpus), and Acacia (Robinia pseudoacacia), to determine their suitability for constructing long-span roof trusses. These are available in the South Western part of Nigeria. Their mechanical properties;bending strength, compressive strength, shear strength, tensile strength, Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and density, were determined in the laboratory. The results obtained showed that all the timber types, except Terminalia superba (Afara), have higher values of mechanical properties than the values that are obtainable for classes of strength D30 to class D70 in the British Code of Practice. It means these species are of higher quality than the stipulated strength classes in the British code. The results also show that the order of relevance of the species for structural design (or work) is Acacia (Robinia pseudoacacia), Ayin (Anogeissus leiocarpus), Gmelina Arborea, and Tectona grandis (Teak). Terminalia superba (Afara) is not recommended for structural works.
文摘The twenty-first century is one of the most complex in the history of humanity,mainly due to the ecological crisis it is going through.The construction sector generates about 40%of CO2 emissions into the environment;the foregoing should motivate this sector to seek new alternatives to develop new building practices.Taking these current needs into account,this document classifies and presents a multidisciplinary solution that integrates biology,engineering and architecture to develop a new and innovative lightweight timber structure;it divides with a main structure made of timber and an innovative joint system made of bio-polymers connecting all the panels.Through the study of diatoms,it was able to analyze the bio-morphology of the structure,joints and in particular the geometry since they were the inspiration for the design of this structure that presents an innovative and novel design of structural optimization.Through parametric design and digital fabrication,it was able to create a complex geometry that obtains excellent structural behavior.This research discusses and explores how materials,geometry led to the optimization of a structure and how new structures can arise,thanks to biology new solutions can be obtained that are completely sustainable,being a clear example of how to combat the effects of the climate change and in a precise way it highlights the advantages of the bio-design in the architectural design.
文摘This project deals with architecture and engineering involved in the process of architectural design.Based on native irregular components,it aims at developing an innovative approach in the conception and rationalization of non-standard structures.Contemporary architecture and its non-classical structures require the design of customized pieces.This process which is highly energy and resources consumptive does not always take into account the inherent material properties.This project develops a way of optimizing,in architectural structures,the use of native wood pieces that are not industrially transformed(e.g.boughs)or of reused pieces of carpentry.As a consequence,the ecological footprint of the structures would be reduced.
文摘Two analytical procedures (Crank's method and Dincer's method) for porous solid materials were reevaluated and used to determine moisture diffusion coefficients and moisture transfer coefficients for larch lumber subjected to drying. A diffusion-like equation was used to describe drying process data. The lumber was idealized in the modeling as infinite plates. The moisture transport process inside the board was assumed to be one-dimensional. The macroscopic drying kinetics curves of larch timber at particular conditions were determined experimentally. Based on these data, calculation for both the moisture diffusion coefficients and moisture transfer coefficients by the Dincer's analytical procedure were made. The dynamic moisture diffusion coefficients by the traditional Crank's method were calculated. In general, diffusion coefficients calculated by the Dincer's method were all higher than those by Crank's method. These results could be due to the differences between two analytical methods and also different characteristics between solid moisture diffusion process and heat transfer process. Therefore the analysis and solution procedures of moisture diffusion differential equations need to be adapted in the future. With drying temperature's increasing moisture diffusion coefficient (D) and moisture transfer coefficient (k) increases accordingly. Also the relationships between diffusion coefficients and temperature as well as material moisture contents were analyzed by using Arrhenius equation and bound water transport theory.
文摘Objective:To document ethnobotanical informations of useful woody plant species in the region of Kotli,Azad Kashmir.Methods:An ethnobotanical survey was conducted in Kotli.Data were collected by interview and semi structured questionnaire from selected local informants and traditional practitioners as well as by field assessment.Results:The present study documented the etnobotanical uses of 33 woody plant species.Most of the species have been used for dual purpose.Only 5 species are used for one purpose.Study revealed all species have medicinal value,among which 21 were used as fuel wood species,16 as fodder species,4 as timber wood species,12 as edible fruit species,6 as fence or hedge plant,7 as ornamental species and 12 species had other uses.Conclusions:Medicinal plants are still widely used for health care by locals of Kotli.Some species of woodlands seem to be vulnerable to overcollection and deforestation.As the young generation is diverted toward allelopathic medicines,ethnobotanical knowledges of important medicinal plants are restricted to the old people only.It is suggested to close the forest of district Kotli for next two to three decades for the conservation of plant biodiversity.
基金financially supported by Texas Tech University in the form of start-up and faculty research enhancement grants
文摘In the megadiverse forests of Southeast Asia, hundreds of timber species are economically important but the population genetics of only a few taxa are known. Cross-specific amplification of microsatellite loci among closely related taxa could enhance our ability to study and manage previously unstudied species. We successfully utilized STMS markers in Shorea platyclados, originally developed for Shorea curtisii. The six primer pairs we tried successfully produced PCR products of expected sizes. The number of alleles observed ranged from 10 to 14 and an average of 12 alleles were detected per locus. A high expected and observed heterozygosity was observed and it ranges from 0.718 to 0.827 among all populations across all six loci tested. Microsatellite DNA markers are highly polymorphic, co-dominant, reproducible, and amenable to high throughput genetic analyses. Overall, the cross- specific amplification of microsatellite loci appears to be complicated by numerous factors. While the approach may be effective for local management and conservation ofpoorly known species, the results must be carefully interpreted.
文摘This study addresses the increasing demand for large-diameter production timber,and considers the time and space variability of half-sib families of Pinus massoniana.Height,diameter at breast height(DBH)and timber volume of 440 open-pollinated half-sib progeny families were investigated in 14 progeny trials in different years and production regions.An evaluation of the genetic variation of all half-sib families was carried out during the sustainable rapid growth period and individual volumes were characterized as a major index.ANOVA analysis showed that there was considerable variance in the growth traits of most families in different years and on different sites.The variations caused by temporal and spatial changes of the mating system required three selection methods for analysis.The results show that there were differences among the heritabilities of different growth traits by different halfsib progenies.Average heritability values of height,DBH and volume were 0.33,0.34 and 0.36,respectively.Fortyfive superior families were selected in every progeny test,12 were selected in progeny trials by different years and five in different habitat progeny trials.Three superior families(Gui GC553A,Gui GC414A and Gui GC431A)were selected,although in different years and production regions.The genetic gains of timber volume of these selected r families ranged from 1.20 to 47.00%,which could provide a foundation for superior wood property selection and serve as material for seed improvement and extension in surrounding areas.
文摘This paper reports on the effect of various micropropagation factors of Gmelina arborea Roxb. through multiple shoot induction. Factors like the source and age of explants, plant growth regulators (PGRs), media composition, and carbon source affected multiple shoot-ing in the present study. Among all the explants used, only shoot tips derived from one, two, and three week old seedlings could form multiple shoots. Besides, the formation of multiple shoots depended on the con-centration and combination of PGRs. Among all the PGRs, BAP (6-benzylaminopurine) alone gave the highest regeneration efficiency. Simi-larly, IBA (Indole-3-butyric acid) was the most efficient PGR in inducing root formation in the microshoots. Media composition and carbon source also affected the regeneration efficiency. MS (Murashige and Skoog medium) proved to be the best media for regeneration followed by B5, SH (Schenk and Hilderbrandt medium) and WPM (Woody plant medium) in that order. Similarly, among sugars, only sucrose and glucose sup-ported induction of microshoots. Based on this study we recommend the use of glucose in place of sucrose in MS medium for maximum regenera-tion efficiency.
基金supported by the German Federal Ministry of Education and Research (BMBF) (No. 0330802A)the Chinese Ministry of Science and Technology (MOST) (No. 2008DFA32070) in the framework of the Sino-German joint project "ValWood-innovative sustainable land use"
文摘We present management tools for growing four valuable broadleaved tree species, indigenous to subtropi.cal southern China. Crown diameter (CD) of the species studied can be predicted very well by using a model that is so e y a near funct on of d ameter at breast he ght (DBH). The add t on of tree age (AGE) and yield class (YC) to this-nodel did not significantly improve its predictive capacity. We used species-specific crown diameter models to calcu- ate the amount of growing space and subsequently stand density that each species needs to achieve desired stem "adial growth rates. Furthermore we used this information to calculate a "distance factor", a rule of thumb that roughly ~stimates the distance between two neighboring trees needed to achieve a desired future target diameter. These tools 'acilitate the planning of thinning regimes by using crown diameter models combined with annual radial growth rates to ;alculate the number of crop trees per hectare required to reach a desired target stem diameter.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2014B-01China Postdoctoral Science Foundation under Grant No.2013M531083+3 种基金Natural Science Foundation of Hei Longjiang Province of China under Grant No.LC2012C32National Natural Science Foundation of China under Grant Nos.513085115150853551208234
文摘On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the 'strong column, weak beam' design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.
基金the National Natural Science Foundation of China(Grant No.31570559 and No.51808293)Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180778).
文摘Eucalyptus is a major fast-grown species in South China,which has the potential for producing structural wood products such as cross-laminated timber(CLT).Aspect ratio(board width vs.board thickness)of eucalyptus lumbers is small due to the small diameter of fast-grown eucalyptus wood.To evaluate its rolling shear modulus and strength for potential CLT applications,three-layer hybrid CLT shear block specimens with different aspect ratios(2,4,6),were tested by planar shear test method.Digital image correlation(DIC)was employed to measure the rolling shear strain distribution and development during the planar shear tests.The mean values of rolling shear modulus and strength of eucalyptus lamination were 260.3%and 88.2%higher than those of SPF(Spruce-pine-fir)lamination with the same aspect ratio of 4,respectively.The rolling shear properties of eucalyptus laminations increased as the aspect ratio increased.Aspect ratio had a significant influence on rolling shear modulus compared to rolling shear strength.The high shear strain regions were primarily found around the gaps between segments of cross layer.The quantity of high shear strain regions increased as the aspect ratio of lamination decreased.Other high shear strain regions also occurred around the pith and along the glue line.The sudden failure of specimen occurred in the high strain region.In conclusion,the rolling shear strength and modulus of fast-grown eucalyptus laminations exceed the respective characteristic values for softwoods in the current standard by roughly factors of 3 and 8,indicating great potential for fast-grown eucalyptus wood cross-layers in CLT.
文摘Tenon-mortise joint is widely used in traditional timber structures around the world.This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and CNC technology instead of traditional material and manual work.30 full-scale tenonmortise joints were manufactured and tested under monotonic loading,and the effects of dimension,shape,processing error and adhesive were evaluated.It was found that the round rectangular shaped tenon-mortise joints were comparable with traditional joints in terms of structural performance,but were time and labor saving.The variability of the proposed tenon-mortise joints was lower,which would benefit the design value.Applying adhesive between tenon and mortise increased the average stiffness by 4.3 times and average moment capacity by 27.4%,respectively.The gaps between wood members had little effect on the capacity and stiffness in monotonic bending but may influence the energy dissipation ability in cyclic bending.This study showed the feasibility of combining the traditional joinery method with modern wood products and manufacturing technology,which may promote the application of tenon-mortise joints in modern timber structures.