This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, co...This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, context, and innovative methodologies, setting the stage for a deep dive into the theoretical underpinnings of sustainable and competitive trade. It explores Ukraine’s rich forest biodiversity across varied vegetation zones and its geopolitical significance. Detailed evaluations of forest resource management, policy frameworks, and institutional support form the core of the analysis. Challenges such as imbalanced export structures and legal inconsistencies are critically examined. The research employs trade gravity models and competitive indicators like the Revealed Comparative Advantage (RCA) and Market Share (MS) to assess factors influencing exports and to forecast potential growth areas. The findings inform strategic recommendations aimed at enhancing export capacity through market diversification, brand development, and legal stability. The conclusion highlights the need for strategic interventions to harness Ukraine’s timber resources sustainably, balancing economic gains with environmental stewardship.展开更多
Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process par...Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process parameters,such as pressure(12 MPa),adhesive spread rate(200 g/m^(2))and adhesive(one-component polyurethane),the mechanical properties of Japanese larch-made cross-laminated timber(CLT)with different lay-ups were evaluated by means of the static method.Results of this study showed that variations in lay-ups significantly affected the mechanical properties of CLT.The strength and modulus of bending and parallel compression for CLT increased with the thickness of lumber,while that of bending,parallel compression and rolling shear all decreased with the number of layers.Thickness,layup orientation and the number of layers all had an impact on the strength of CLT.Failure modes obtained from numerical simulation were basically the same as those of experimental tests.There was also strong alignment between theoretical value and test value for effective bending stifness and shear stifness.Thus,the shear analogy method can be used to predict the mechanical properties of CLT effectively.This study proved great potential in using Japanese larch wood for manufacturing CLT due to its good mechanical properties.展开更多
This study investigated the bending,compression as well as the bonding performance of CLT panels made from fast-growing timber species,i.e.,Laran(Neolamarckia cadamba)and Batai(Paraserianthes falcataria).The variables...This study investigated the bending,compression as well as the bonding performance of CLT panels made from fast-growing timber species,i.e.,Laran(Neolamarckia cadamba)and Batai(Paraserianthes falcataria).The variables studied were timber species(Laran and Batai),layers of lamination(3-layer and 5-layer),loading direction in bending(in-plane and out-of-plane),loading direction in compression(x-,y-,and z-axis)and different treatment conditions for bonding performance test.The desired outputs of this study were bending and compression properties(strength and stiffness)as well as bonding performance(block shear strength,wood failure percentage and delamination value).The bending and compression test were conducted according to EN16351:2015 and EN408:2012,respectively.On the other hand,the bonding performance test was determined by block shear and delamination test based on EN16351:2015 and EN14374:2004,respectively.Prior to block shear test,the samples were subjected to three different treatment conditions.The results showed that CLT made from 3-layer Laran timber,loaded at out-of-plane direction exhibited the highest bending properties.Contrarily,CLT made from 5-layered Batai timber,loaded at in-plane direction showed the lowest bending properties.Laran samples for compression loaded at x-axis exhibited the best compressive properties.Generally,Laran CLT showed greater bonding performance determined by shear test compared to Batai CLT for both 3-and 5-layer panels.On the contrary,delamination results showed that Batai CLT demonstrated better bonding performance compared to Laran CLT.In terms of bonding performance measured by wood failure percentage(WFP),most samples under various treatment conditions showed WFP≥80%except for samples under wet condition with WFP≤60%.展开更多
Cross laminated timber(CLT)is an innovative and environment friendly engineered timber product with superior structural performance.CLT offers strong resistance against both in-plane and out-of-plane loading.Hence,it ...Cross laminated timber(CLT)is an innovative and environment friendly engineered timber product with superior structural performance.CLT offers strong resistance against both in-plane and out-of-plane loading.Hence,it is widely used as floors,roofs or wall elements.Considerable experimental research on CLT under various loading conditions has been done in the recent past.This article presents a comprehensive review of various design methods to determine basic mechanical properties such as tension,compression and rolling shear strength of CLT with primary focus on Norway spruce.All relevant experimental data available from existing literature were collated and consequently been used to evaluate the performance of various methods to design CLT structures.The comparison revealed that different methods show considerable variance in predicting the capacity of CLT panels due to the variation in timber species,which affects the corresponding mechanical properties of the lamella.In addition to species,rolling shear properties can also vary considerably depending on the type of experimental technique used for testing.A predictive model has also been proposed to correlate rolling shear strength obtained from shear analogy method to that obtained using planar shear.展开更多
The out-of-plane shear properties of cross-laminated timber(CLT)substantially influence the overall mechanical properties of CLT.Various testing methods and theories related to these properties have recently been deve...The out-of-plane shear properties of cross-laminated timber(CLT)substantially influence the overall mechanical properties of CLT.Various testing methods and theories related to these properties have recently been developed.The effects of the number of layers(three and five layers)and testing method(short-span three-and four-point bending tests)on the out-of-plane shear properties of CLT were evaluated.The out-of-plane shear strength values were calculated based on different theories for comparison.The failure mode in the short-span four-point bending(FPB)method was mainly the rolling shear(RS)failure in the cross layers,indicating that the FPB method was appropriate to evaluate the RS strength of CLT.The out-of-plane shear capacity obtained using the three-point bending(TPB)method was higher than that tested by the FPB method.The testing methods significantly influenced the out-of-plane shear capacity of the three-layer specimens but not that of the five-layer specimens.With an increase in the number of layers,the out-of-plane shear strength of the specimens decreased by 24%.A linear correlation was found among the shear strength values obtained from different theories.展开更多
Understanding the economic feasibility of cross-laminated timber(CLT),an emerging and sustainable alternative to concrete and steel,is critical for the rapid expansion of the mass timber industry.However,previous stud...Understanding the economic feasibility of cross-laminated timber(CLT),an emerging and sustainable alternative to concrete and steel,is critical for the rapid expansion of the mass timber industry.However,previous studies on economic performance of CLT have not fully considered the variations in the feedstock,plant capacities,manu-facturing parameters,and capital and operating costs.This study fills this gap by developing a techno-economic analysis of producing CLT panels in the Southern United States.The effects of those variations on minimum sell-ing price(MSP)of CLT panels are explored by Monte Carlo simulation.The results show that,across all the plant capacities from 30,000 to 150,000 m^(3)/year,the MSP ranges from$345 to$609/m^(3) with a±6%–9%range caused by the variations in feedstocks,key manufacturing parameters,capital and operating cost.The MSP decreases sig-nificantly along the increasing capacities.A sensitivity analysis exhibits that the lumber price,lumber preparing loss,plant capacity,and the installed costs of layering and gluing,finishing,and miscellaneous,are the top driving factors to CLT MSP.Supported by Geographic Information System,this study also studies the transportation cost of delivering CLT to customers under three CLT demanding levels(1%,5%,15%).The results show that the trans-portation cost is 1%–8%of the MSP.Lower demanding level or higher plant capacity can increase the transporta-tion cost due to average longer delivering distance.When considering the delivered cost that sums MSP and transportation cost,larger plant capacity does not necessarily generate lower delivered cost.展开更多
In order to explore a kind of high-strength,earthquake-resistant,eco-nomical and suitable connection,4 groups of cross-laminated timber wall-to-floor and wall-to-wall bolted connections were tested under monotonic and...In order to explore a kind of high-strength,earthquake-resistant,eco-nomical and suitable connection,4 groups of cross-laminated timber wall-to-floor and wall-to-wall bolted connections were tested under monotonic and cyclic load-ing.The defommation characteristics and failure modes of the cross-laminated tim-ber wall-to-floor and wall-to-wall bolted connections were exploited.Load-slip curves,bearing capacity,yielding point,stiffness and ductility of each group of specimens were analyzed.The test results indicate that the loading process of cross-laminated timber bolted connections under tension can be categorized as five stages,namely the elastic stage,the slip stage,the embedding stage,the yield-ing stage and the ultimate stage.The ultimate tensile capacity of cross-laminated timber bolted wall-to-floor connections is 2.67 times that of the wall-to-wall bolted connections.Compared with cross-laminated timber self-tapping screwed connections,the ultimate tensile capacity of the cross-laminated timber wall-to-floor bolted connections is 2.70 times that of the self-tapping screwed connec-tions,and the ultimate tensile capacity of the cross-laminated timber wall-to-wall bolted connections is 3.83 times that of the self-tapping screwed connections.The crosslaminated timber bolted connections have larger yielding displacement and wider plastic range,and they are more energy dissipative and more ductile.Furthermore,the cost of the cross-laminated timber wall-to-floor bolted connec-tions is 46%that of the self-tapping screwed connections,while the cost of cross-laminated wall-to-wall bolted connections is 53%that of the self-screwed connections.展开更多
To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending ...To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.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
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
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 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
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 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
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
文摘This paper conducts a comprehensive analysis of the export dynamics within the Ukrainian timber industry, emphasizing its pivotal role in the national economy. The study begins by outlining the research objectives, context, and innovative methodologies, setting the stage for a deep dive into the theoretical underpinnings of sustainable and competitive trade. It explores Ukraine’s rich forest biodiversity across varied vegetation zones and its geopolitical significance. Detailed evaluations of forest resource management, policy frameworks, and institutional support form the core of the analysis. Challenges such as imbalanced export structures and legal inconsistencies are critically examined. The research employs trade gravity models and competitive indicators like the Revealed Comparative Advantage (RCA) and Market Share (MS) to assess factors influencing exports and to forecast potential growth areas. The findings inform strategic recommendations aimed at enhancing export capacity through market diversification, brand development, and legal stability. The conclusion highlights the need for strategic interventions to harness Ukraine’s timber resources sustainably, balancing economic gains with environmental stewardship.
基金by basic operating budget of scientific research institutes for public welfare at the central level(CAFBB2018SY032)China Postdoctoral Science Foundation (No.2018M641225).
文摘Japanese larch is one of the main plantation tree species in China.A lack of engineered wood products made by Japanese larch,however,limits its application in wood stnuctures.In this study,based on optimum process parameters,such as pressure(12 MPa),adhesive spread rate(200 g/m^(2))and adhesive(one-component polyurethane),the mechanical properties of Japanese larch-made cross-laminated timber(CLT)with different lay-ups were evaluated by means of the static method.Results of this study showed that variations in lay-ups significantly affected the mechanical properties of CLT.The strength and modulus of bending and parallel compression for CLT increased with the thickness of lumber,while that of bending,parallel compression and rolling shear all decreased with the number of layers.Thickness,layup orientation and the number of layers all had an impact on the strength of CLT.Failure modes obtained from numerical simulation were basically the same as those of experimental tests.There was also strong alignment between theoretical value and test value for effective bending stifness and shear stifness.Thus,the shear analogy method can be used to predict the mechanical properties of CLT effectively.This study proved great potential in using Japanese larch wood for manufacturing CLT due to its good mechanical properties.
文摘This study investigated the bending,compression as well as the bonding performance of CLT panels made from fast-growing timber species,i.e.,Laran(Neolamarckia cadamba)and Batai(Paraserianthes falcataria).The variables studied were timber species(Laran and Batai),layers of lamination(3-layer and 5-layer),loading direction in bending(in-plane and out-of-plane),loading direction in compression(x-,y-,and z-axis)and different treatment conditions for bonding performance test.The desired outputs of this study were bending and compression properties(strength and stiffness)as well as bonding performance(block shear strength,wood failure percentage and delamination value).The bending and compression test were conducted according to EN16351:2015 and EN408:2012,respectively.On the other hand,the bonding performance test was determined by block shear and delamination test based on EN16351:2015 and EN14374:2004,respectively.Prior to block shear test,the samples were subjected to three different treatment conditions.The results showed that CLT made from 3-layer Laran timber,loaded at out-of-plane direction exhibited the highest bending properties.Contrarily,CLT made from 5-layered Batai timber,loaded at in-plane direction showed the lowest bending properties.Laran samples for compression loaded at x-axis exhibited the best compressive properties.Generally,Laran CLT showed greater bonding performance determined by shear test compared to Batai CLT for both 3-and 5-layer panels.On the contrary,delamination results showed that Batai CLT demonstrated better bonding performance compared to Laran CLT.In terms of bonding performance measured by wood failure percentage(WFP),most samples under various treatment conditions showed WFP≥80%except for samples under wet condition with WFP≤60%.
文摘Cross laminated timber(CLT)is an innovative and environment friendly engineered timber product with superior structural performance.CLT offers strong resistance against both in-plane and out-of-plane loading.Hence,it is widely used as floors,roofs or wall elements.Considerable experimental research on CLT under various loading conditions has been done in the recent past.This article presents a comprehensive review of various design methods to determine basic mechanical properties such as tension,compression and rolling shear strength of CLT with primary focus on Norway spruce.All relevant experimental data available from existing literature were collated and consequently been used to evaluate the performance of various methods to design CLT structures.The comparison revealed that different methods show considerable variance in predicting the capacity of CLT panels due to the variation in timber species,which affects the corresponding mechanical properties of the lamella.In addition to species,rolling shear properties can also vary considerably depending on the type of experimental technique used for testing.A predictive model has also been proposed to correlate rolling shear strength obtained from shear analogy method to that obtained using planar shear.
基金by National Natural Science Foundation of China(Grant No.31570559)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘The out-of-plane shear properties of cross-laminated timber(CLT)substantially influence the overall mechanical properties of CLT.Various testing methods and theories related to these properties have recently been developed.The effects of the number of layers(three and five layers)and testing method(short-span three-and four-point bending tests)on the out-of-plane shear properties of CLT were evaluated.The out-of-plane shear strength values were calculated based on different theories for comparison.The failure mode in the short-span four-point bending(FPB)method was mainly the rolling shear(RS)failure in the cross layers,indicating that the FPB method was appropriate to evaluate the RS strength of CLT.The out-of-plane shear capacity obtained using the three-point bending(TPB)method was higher than that tested by the FPB method.The testing methods significantly influenced the out-of-plane shear capacity of the three-layer specimens but not that of the five-layer specimens.With an increase in the number of layers,the out-of-plane shear strength of the specimens decreased by 24%.A linear correlation was found among the shear strength values obtained from different theories.
文摘Understanding the economic feasibility of cross-laminated timber(CLT),an emerging and sustainable alternative to concrete and steel,is critical for the rapid expansion of the mass timber industry.However,previous studies on economic performance of CLT have not fully considered the variations in the feedstock,plant capacities,manu-facturing parameters,and capital and operating costs.This study fills this gap by developing a techno-economic analysis of producing CLT panels in the Southern United States.The effects of those variations on minimum sell-ing price(MSP)of CLT panels are explored by Monte Carlo simulation.The results show that,across all the plant capacities from 30,000 to 150,000 m^(3)/year,the MSP ranges from$345 to$609/m^(3) with a±6%–9%range caused by the variations in feedstocks,key manufacturing parameters,capital and operating cost.The MSP decreases sig-nificantly along the increasing capacities.A sensitivity analysis exhibits that the lumber price,lumber preparing loss,plant capacity,and the installed costs of layering and gluing,finishing,and miscellaneous,are the top driving factors to CLT MSP.Supported by Geographic Information System,this study also studies the transportation cost of delivering CLT to customers under three CLT demanding levels(1%,5%,15%).The results show that the trans-portation cost is 1%–8%of the MSP.Lower demanding level or higher plant capacity can increase the transporta-tion cost due to average longer delivering distance.When considering the delivered cost that sums MSP and transportation cost,larger plant capacity does not necessarily generate lower delivered cost.
基金This study is funded by the Fundamental Research Funds for the Central Universities(Program No.22120180315).
文摘In order to explore a kind of high-strength,earthquake-resistant,eco-nomical and suitable connection,4 groups of cross-laminated timber wall-to-floor and wall-to-wall bolted connections were tested under monotonic and cyclic load-ing.The defommation characteristics and failure modes of the cross-laminated tim-ber wall-to-floor and wall-to-wall bolted connections were exploited.Load-slip curves,bearing capacity,yielding point,stiffness and ductility of each group of specimens were analyzed.The test results indicate that the loading process of cross-laminated timber bolted connections under tension can be categorized as five stages,namely the elastic stage,the slip stage,the embedding stage,the yield-ing stage and the ultimate stage.The ultimate tensile capacity of cross-laminated timber bolted wall-to-floor connections is 2.67 times that of the wall-to-wall bolted connections.Compared with cross-laminated timber self-tapping screwed connections,the ultimate tensile capacity of the cross-laminated timber wall-to-floor bolted connections is 2.70 times that of the self-tapping screwed connec-tions,and the ultimate tensile capacity of the cross-laminated timber wall-to-wall bolted connections is 3.83 times that of the self-tapping screwed connections.The crosslaminated timber bolted connections have larger yielding displacement and wider plastic range,and they are more energy dissipative and more ductile.Furthermore,the cost of the cross-laminated timber wall-to-floor bolted connec-tions is 46%that of the self-tapping screwed connections,while the cost of cross-laminated wall-to-wall bolted connections is 53%that of the self-screwed connections.
文摘To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.
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).
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.
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.