Characteristics Of Timber Research Articles

Long-Term Behavior of Timber–Concrete Composite Structures: A Literature Review on Experimental and Numerical Investigations

Timber–concrete composite structure is a type of efficient combination form composed of concrete floors and timber beams or floors through shear connectors, and shows good application potential in the floor system of timber buildings. The long-term performance of the timber–concrete composite structures is complex and is affected by the creep of timber and concrete, as well as the long-term slip of the shear connectors. This article presents a comprehensive overview of the research status on the long-term behavior of timber–concrete composite members and different shear connectors. For the shear connectors, the effects of loading levels, environments, and component materials on their creep coefficients are summarized. As to the timber–concrete composite members, both the experimental and numerical investigations are gathered into discussions: the connection types, component materials, loading conditions, and durations in the long-term tests are also discussed; various models for describing long-term behavior of timber, concrete, and connection systems are provided, and then a comprehensive description of the progress of numerical investigations over the last decades is made. In addition, the suggestions for future research are proposed to reach a clearer understanding of the bending mechanisms and mechanical characteristics of timber–concrete composite structures.

Application of Graphic Statics and Strut-and-Tie Models Optimization Algorithm in Innovative Timber Structure Design

Timber has long been extensively employed within the construction industry as a famous, environmentally friendly, and low-carbon material. Considering that construction constitutes one of the most significant contributors to carbon emissions throughout the entire life-cycle of a building, there is an urgent desire to incorporate timber into this domain. Nevertheless, the use of timber faces inherent challenges stemming from its anisotropic nature, a result of the natural growth of timber fibers, which makes it challenging for it to function as a primary load-bearing material in coping with the various complex stresses inherent in architectural applications. Numerous designers have attempted to address this limitation through over-sized members and reinforcement at joints; however, none have satisfactorily resolved this issue in an economical manner. In this article, we introduce the Strut-and-Tie models (STM) from Graphic Statics (GS) and a topological optimization algorithm. This algorithm has the capability to generate a ‘load-minimizing path’ STM based on external load support conditions and the maximum structural path span. Regardless of the complexity of the initial external loads, each load transfer path in the optimized STM bears loads in only one direction, representing an optimal solution with minimal internal loads that align seamlessly with the characteristics of timber. Consequently, we endeavor to adopt this optimization algorithm to propose a structural design methodology, with the aspiration of designing structural systems that harness the unique attributes of timber perfectly and applying them to various architectural scenarios. Ultimately, we conclude that structural systems designed based on optimized STM are adaptable to diverse architectural contexts, and when applied to small-scale buildings, this method can save approximately 20% of material consumption compared to conventional timber frame structures, while in the case of mid-rise to high-rise buildings, it can lead to a material savings of approximately 5%.

Characterization of the chloroplast genome of Dalbergia latifolia (Fabaceae) and its phylogenetic relationship with other Dalbergia species

Dalbergia latifolia Roxb. has high economic and ecological value owing to its durable timber characteristics. In the present study, a near complete chloroplast (Cp) genome of D. latifolia was assembled from leaf transcriptome data using reference‐based assembly. The Cp genome was 158 966 bp long and contained 116 genes, including 32 tRNAs, 4 rRNAs and 80 protein coding genes. Microsatellite analysis revealed the presence of 315 SSRs in the Cp genome. In a phylogenetic tree constructed using the complete Cp genomes of 27 species of Dalbergia, D. latifolia clustered with D. cochinchinensis and D. obtusifolia. The highly resolved tree grouped the species from Africa and South America and separated D. assamica and D. balansae as distinct species. Dalbergia barienesis, sometime considered a synonym of D. oliveri, was resolved as the sister of D. oliveri but showed significant divergence from D. barienesis. The newly generated Cp genome is a resource much needed to accelerate phylogenomic and evolutionary studies in D. latifolia. It will also facilitate development of super barcodes for timber forensics.

Automatic estimation of annual ring profiles in Norway spruce timber boards using optical scanning and deep learning

In softwood species, annual ring width correlates with various timber characteristics, including the density and modulus of elasticity along with bending and tensile strengths. Knowledge of annual ring profiles may contribute to more accurate machine strength grading of sawn timber. This paper proposes a fast and accurate method for automatic estimation of ring profiles along timber boards on the basis of optical scanning. The method utilizes two 1D convolutional neural networks to determine the pith location and detect the surface annual rings at multiple cross-sections along the scanned board. The automatically extracted rings and pith information can then be used to estimate the annual ring profile at each cross-section. The proposed method was validated on a large number of board cross-sections for which the pith locations and radial ring width profiles had been determined manually. The paper also investigates the potential of using the automatically estimated average ring width as an indicating property in machine strength grading of sawn timber. The results indicated that combining the automatically estimated ring width with other prediction variables can improve the accuracy of bending and tensile strength predictions, especially when the grading is based only on information extracted from optical and laser scanning data.

Experimental investigation of timber samples under triaxial compression conditions

Timber is re-emerging as a prominent structural material in construction due to its sustainability and aesthetic features. Timber is increasingly used in composite elements made along with steel and concrete. In the composite elements, timber is subjected to a triaxial confined stress state. However, the characteristics of timber under triaxial stress state are not well understood. An experimental campaign was carried out to characterise the triaxial confined behaviour of timber samples. Two types of timbers (soft and hardwood) were used in the experimental campaign. The selected timber samples were subjected to confined and unconfined axial compression loading conditions. In total, 50 samples were tested with five different lateral confining pressures (unconfined, 3, 5, 8 and 12 MPa). The experimental results are presented in terms of compressive strengths and axial compression stress-strain curves. The experimental data obtained was used to define the critical parameters of confined timber, such as confined strength, strain at peak stress and stress-strain behaviour. Test results demonstrate that the confinement pressure improves the strength and ductility, and the conventional Mohr-Coulomb criterion can be used to represent the confined timber strength and strain evolution. Finally, based on the data gathered, a suitable constitutive model to characterise the stress-strain behaviour of timber under the triaxial confined stress-state is proposed. This model is similar to the constitutive models typically used for concrete, mortar and rock under confined stress state. However, differences are highlighted in timber in terms of strength gain and ductility.

Application of Wooden Modular Construction for the Needs of the Elderly

In recent years, changes in demographic structure have been observed worldwide. To sustain the growing population of elderly people with special needs, homes need a radical rethink both in designing new houses and in retrofitting new solutions to existing houses. Designs that facilitate aging in place, designs that maintain thermal comfort, and designs that have net-zero energy demands and low to zero to negative carbon footprints are needed. The article discusses the issues of construction for the elderly. The trends in the demographic development of society in selected countries are presented. Additionally, information on the housing stock for elderly people in Poland is provided. The carbon dioxide emission limits to mitigate climate change make it necessary to find an alternative to concrete and steel, traditional construction materials. In this context, Cross Laminated Timber (CLT) fulfills the sustainability requirements. However, to select the suitable panel a detailed analysis of timber characteristics is required. It is necessary to evaluate mechanical properties in bending, tension, compression, and shear. Since the mechanical properties of certain types of wood differ, their proper selection is challenging. The multi-criteria analysis could address this. In this article, four wood species, spruce, oak, ash, and beech, were evaluated using the Analytic Hierarchy Process (AHP) analysis. Based on the type of construction elements and their functions, analyses were using six mechanical properties as criteria. The optimal type of wood was indicated.

Quality traits of plantation Eucalyptus nitens logs impacting volume and value recovery of structural sawn boards

Plantations of Eucalyptus species are planted and grown worldwide for short rotations and with limited silvicultural treatments mostly to produce pulplogs for the pulp and paper industry. These resources could be used as raw material for construction timber, to support the increasing need of renewable resources from the building sector. To use fast-grown Eucalyptus logs as a source of sawn timber log grading standards are needed, which can be developed accounting for log characteristics impacting sawn timber recovery. This study aims to examine the quality of fast-grown Eucalyptus logs and relate relevant log quality traits to sawn timber characteristics. Wood quality and log characteristics of forty-nine fast-grown Eucalyptus logs and the characteristics and structural properties of 268 sawn boards milled from those logs were investigated. Significant differences were found in wood quality characteristics from logs sourced from different positions in the stem. However, sawn boards did not differ in their wood quality traits according to log position, which influenced only the amount and type of knots on the board surface and some structural properties. Moreover, log characteristics including volume, taper, log end splits and stiffness significantly impacted important board recovery traits. The results of this study show that log characteristics such as volume, taper, log end splits and stiffness should be accounted for in log grading standards seeking to grade fast-grown Eucalyptus resources for different product classes.

Wood moisture monitoring and classification in kiln‐dried timber

Different mass timber structures require a specific range of wood moisture. Thus, moisture monitoring is a crucial quality control task during timber drying that impacts the properties and quality of the subsequent timber structures. Variations in the average and distribution of the final moisture can result in significant variations in the timber properties and thus negatively affect performance in service. This necessitates rigorous moisture monitoring and timber grading during and after kiln drying. This study aims to estimate the kiln-dried population final moisture distribution based on green timber characteristics and machine learning. This will facilitate the timber grading process by reducing the variation in the mechanical properties of the kiln-dried timber, as timbers with a higher chance of moisture variation will be identified before the drying process. Timber initial moisture, initial weight, basic density, and target moisture were used to train machine learning models. Linear discriminant analysis and decision tree were used for moisture classification. Principal component and variable clustering analysis were performed to study the critical parameters affecting the timber overdrying and underdrying. The results indicated that initial moisture level and weight are the essential variables, while density had the least significant effect on the performance of classification models. The decision tree approach exhibited better performance than discriminant analysis with ~91% classification accuracy proving the effectiveness of using initial timber properties for quality control and grading of kiln-dried timber.

Effects of faults in the application of fire retardants in correlation with the efficiency of fire retardant materials on fire performance

PurposeFire protection regulations are difficult to comply with in the case of wooden structures because of the fact that wood is a combustible material. The fire protection of wood can be solved with coatings or by the application of flame retardants.Design/methodology/approachThe standard of MSZ EN 1995‐1‐2 currently does not allow the consideration of fire retardants in case of scaling the fire load. In spite of the aforementioned, today there are many types of retardants on the market that are reliable and allow us to achieve a better fire protection classification.FindingsThe question is how sensitive a wood preservative is to a construction fault, or what would be the result of the erroneously applied fire retardant to the fire protection characteristics of timber used in constructions.Originality/valueDuring the research, five different fire retardants were tested on three types of wood and their behaviour was monitored under controlled laboratory circumstances. When selecting the wood, it was important to take the wood species that are most commonly used in the construction industry, and their density should be as different as possible. During the tests, the wood preservative was applied incorrectly, modelling the following cases: applying less or more wood preservatives, and creating small and large faults.

Finite element modelling of timber infilled steel tubular short columns under axial compression

Timber infilled steel tubular (TIST) columns can be a promising alternative to the concrete infilled steel tubular (CIST) columns, particularly for the lightly loaded prefabricated structures, as timber is lighter and more sustainable material than the conventional concrete. However, limited research studies were dedicated to investigate the structural behaviour of TIST columns. Therefore, in this study an attempt has been made to investigate the parameters that influence the compressive behaviour and to develop appropriate design guidelines through finite element (FE) analyses of TIST columns. A three-dimensional FE modelling technique of TIST has been developed and validated with available experimental results. The developed model considered the steel tube induced confinement on the strength and orthotropic characteristics of timber as well as contact interaction between steel and timber. The validated modelling technique has been extended to parametrically (120 FE models) study the compressive behaviour of TIST columns varying parameters such as strength properties of steel and timber, thicknesses of steel tube, and cross-sectional shapes. The analyses reveal that the TIST columns can be used on par with CIST columns. The calculated strength and ductility indices reveal that the maximum strength and ductility enhancement up to 60% and 65% can be achieved with TIST. Further, the parametric analyses results have been used to verify suitable design formulations for TIST column, subsequently the design formations that are similar to CIST columns can consciously be extended to design the TIST columns.

Criminal legal and criminalistic characteristicsof timber materials smuggling (Article 226.1 of the Criminal Code of the Russian Federation)

Criminal legal and criminalistic characteristicsof timber materials smuggling (Article 226.1 of the Criminal Code of the Russian Federation)

Wood Science Characteristics of Timber from Pine Deadwood Trees (<i>Pinus sylvestris L.</i>)

During the last decade, the drying up of medieval, arriving and mature stands of pine (Pinus sylvestris L.), which is the dominant breed in domestic forests (33% of the total area, about 45% of the volume of logging), acquired a threatening scale in Ukraine. Dated 2019, the total area of arable crops has reached 413 thousand hectares (of which pines - 222 thousand hectares), or about 4% of the area of the forest fund of Ukraine. One of the main and most effective means of preventing the widespread pathological processes in forests, which cause their drying, is sanitary and other felling of forest care. As a result, a significant amount of untreated low-quality timber, which is classified as deadwood is formed. Timber from deadwood trees is characterized by features such as mycological and insecticidal lesions, cracks, etc., the impact of which on the strength and operational characteristics of timber products has not yet been studied. The interest of using of the wood in the construction as a material from renewable eco-friendly raw materials has traditionally increased. One of the possible uses pine deadwood trees may be the production of structural lumber. The lack of timber characteristics of such timber makes it impossible to predict its behavior during processing and operation and, accordingly, complicates the determination of directions of its rational use, especially in structures. The significantly lower cost of timber from pine deadwood trees, compared with timber from non-attenuated drying out pine trees, is an attractive feature of such raw materials from an economic aspect.

Failure mechanism and safety control strategy for laminated roof of wide-span roadway

The laminated roof of wide-span roadway is characterized by large subsidence, easy instability and difficult support. The open-off cut of #30102 working face in Nanliang coal mine is taken as an example to expound the roof failure mechanism. The roof exploration test are carried out to reveal geologic characteristics. The parametric asymmetric Voronoi block generation program is developed by Python, and the parametric modeling of laminated strata is first implemented in UDEC, then, the numerical model of roadway is established by combining the results of exploration test, microproperties calibration, tension and shear test of rockbolt, and bearing characteristics of timber. It can be concluded that the main types of joint failure are dominated by tensile through numerical calculation. The joint failure height is independent of the roadway width, and when the roadway width is greater than the limit span of the combination beam, there will be roof caving. Based on above analysis, the “rockbolt + timber” combined support technology is proposed, which can combine the roof strata and further reduce the roof span. Numerical simulation results and field application results show that this support scheme can effectively realize the safety control of the laminated roof of the wide-span roadway.

Bending Strength Properties of Keruing and Light Red Meranti in Structural Size in Accordance with Eurocode 5

In designing timber structures based on Eurocode 5, the referencestrength data are given in EN338 where the data are formulated from testing structural size specimens. Malaysian standard established strength grouping using grade stresses based on small clear specimens where as in EN 338 is in characteristic strength. . Therefore, it’s important to obtain the data of strength properties from the structural size specimen as its represent the real behavior of the timber even though the timber strength might be reduce due to the nature of the timber characteristics. This paper reports the investigation on the bending strength properties of keruing and light red meranti from the Malaysian tropical hardwood species in structural size in accordance with EN408. The characteristic values of bending strength, mean modulus, and density are 47.63 N/mm2, 19440.3N/mm2 and 603.38kg/m3, respectively for keruing and 23.05N/mm2, 12182.19 N/mm2 and 302.39kg/m3 respectively for light red meranti. At this moment Keruing can be group in strength class D40 and light red meranti in class D25. These results were different from BS 5268 where Keruing is grouped as D50 and light red meranti as C22 in MS 544 Part 2.

Utilization of Satoyama felled wood from the viewpoint of timber characteristics

Utilization of Satoyama felled wood from the viewpoint of timber characteristics

Growth of Sorbus torminalis after release from prolonged suppression

Continuously suppressed S.torminalis trees were found to be highly sensitive to release cuttings. After release diameter growth increased drastically, the crown redensified from the inside and seeds were produced during the first growing season. Sorbustorminalis is valued for its timber characteristics and ecological role in cultural landscapes. Due to its increased drought tolerance, the species is of growing interest in the context of silviculturally driven climate change adaptation measures. Due to its comparably slow growth, it often forms a second canopy layer below other deciduous tree species. With regard to its ecological and economic value, forest practitioners need to know whether releasing these continuously suppressed individuals from competition is worth it. Therefore, the objective of this study was to examine the effect of release cuttings on the crown growth and radial increment of S.torminalis heavily suppressed by surrounding sessile oaks (Quercuspetraea). We observed changes of shoot and diameter growth within the first year following release cuttings. The overall average annual shoot growth more than tripled when compared to pre-release growth patterns (from 1.9 to 6.2 cm). The greatest release effects were found in the inner part of the crown. The majority of the shoots forming the crown periphery developed fruits and showed only restrained increment. Crown redensification from inside was accompanied by the development of epicormic branches in previously branch-free bole sections. Following release cuttings, diameter growth increased by several orders of magnitude. Altogether, release cuttings seem to have a very positive effect on the vitality of continuously suppressed S.torminalis trees. All released trees grew vigorously and developed fruits throughout the crown surface. Thus, release cuttings may facilitate species propagation and reduce inbreeding effects.

Behaviour of strengthened timber beams using near surface mounted Basalt Fibre Reinforced Polymer (BFRP) rebars

Reinforcement of structural timber members with fibre reinforced polymer (FRP) rods offers merits over that of the conventional steel type. In recent times, near surface mounted (NSM) FRP reinforcement with timber has emerged as a promising alternative for reinforcing timber structures in both flexural and shear loading configurations. Previous investigations have shown that NSM FRP reinforcement technique has higher bond performance than externally bonded equivalents because it (NSM FRP technique) is able to utilise the full capacity of the FRP materials. In spite of these merits, the investigations and the use of this innovative technique are limited. In this paper, an experiment was conducted to investigate the bond characteristics and performance of NSM basalt FRP reinforcement with solid timber structures. In order to predict the performance of the reinforced beam structures, unreinforced control timber members of the same timber characteristics were tested. The results showed that the average bond capacity of the NSM FRP reinforced members was 16% higher than the corresponding unreinforced beams.

Caracterización de productores forestales en 12 estados de la República Mexicana

El trabajo se realizó en los estados de Chihuahua, Durango, Jalisco, Michoacán, Guerrero, Oaxaca, Puebla, Estado de México, Chiapas, Quintana Roo, Veracruz y Campeche con el objetivo de generar una base de datos (BD) relacional con el objetivo de conocer quiénes son los productores forestales, las características básicas de su sistema productivo: escala, nivel de integración vertical, cantidad y características de los aprovechamientos maderables y no maderables, así como obtener información pertinente que contribuya a la toma de decisiones del sector gobierno, social y privado. Se realizó una revisión exhaustiva de los permisos de aprovechamiento forestal maderable y de los avisos de aprovechamiento no maderable otorgados por la Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT). La BD se complementó con información de la Comisión Nacional Forestal (CONAFOR), el Registro Agrario Nacional (RAN), el Instituto Nacional de Estadística y Geografía (INEGI), y otras instituciones que administran información relativa al sector forestal. Como resultado la BD identifica para cada uno de los 12 estados de la república, el número de autorizaciones de aprovechamiento por entidad y tipo y la caracterización de los productores: productores forestales de materias primas maderables, productores forestales no maderables y productores potenciales con capacidad de transformación y comercialización. Se generó una cobertura digital utilizando ArcGIS©, que permite conocer la localización geográfica de los predios con producción maderable en cada estado de la república contemplados en el estudio.

Extraction of timber and non-timber products from the Swamp Forest of Lokoli (Benin): use patterns, harvesting impacts and management options Extraction de bois et de produits non ligneux de la Forêt Marécageuse de Lokoli (Bénin): utilisations, impacts d'exploitation et options d'aménagement Extracción de productos maderables y no maderables en el bosque de pantano, Lokoli (Benín): patrones de uso, impactos de

SUMMARY The study of anthropogenic impacts on tropical forests is vital in the design and development of sustainable extraction systems for both timber and non-timber products. However, distinguishing non-timber forest products (NTFPs) harvesting impacts from timber extraction consequences on the vegetation could be difficult, since tropical forest species often have a multipurpose status. This study explores the purposes and characteristics of timber and non-timber products usage in the Swamp Forest of Lokoli (in the south of Benin Republic) and assesses extraction impacts on the forest dynamics. We used structural parameters analysis and ecological indices to explain the vegetation structure and the species responses to anthropogenic pressures. The results suggest that the forest is being devastated by extraction activities of the local people including both timber collection and non-timber harvesting. Finally, this paper suggests that management policies balancing socio-economic and conservation priori...

Assessment of a solar‐assisted infrared timber drying system

This study investigates convective‐infrared drying characteristics of timber. The biggest disadvantage of infrared heating systems is the uncontrollable rise of the surface temperature up to extremely high values, which causes damage to the product. In this study, the power of an infrared system was controlled and adjusted according to the surface temperature of the product. In doing so, the surface temperature of the infrared heater was prevented from reaching up to values that could damage the product. During the analysis, the surface temperature of the timbers was kept at an average of 65°C, while the bottom temperature was kept at an average of 45°C. The air collector used in the system was found to be 50% efficient. At the end of a 13‐h drying period, the moisture content of pine timbers could be reduced from 1.42 to 0.0948 g water/g dry matter. During the system analysis, parameters such as moisture content, mass diffusion coefficient, and useful energy rate were taken into consideration. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1875–1881, 2017