Timber Size Research Articles

Burma Padauk Timber Column Strengthening with Typical Box Built-Up under Compression-Parallel-to-Grain Load

This study investigated and presented the results of strengthening short stub columns made from Burma Padauk timber using three different timber sizes and three distinct timber types. The strengthening method employed a typical box-built-up configuration, where four equal-sized timbers were adhered to all four surfaces of the column. A total of 12 short stub columns were tested under compression-parallel-to-grain loading. Compressive strength was measured at a 0.05% strain offset, and the failure modes observed in all specimens were documented and analyzed. Interestingly, the compressive load capacity was not significantly affected by the three wood types (Burma Padauk, Tabek, and Teak) representing hardwood, medium hardwood, and softwood, when the total cross-section area remained constant. However, an increase in the total cross-sectional area of the strengthening did lead to a noticeable increase in the compressive load capacity. The observed failure modes were crushing for Burma Padauk and Tabek timbers, while the strengthened softwood timber (Teak) exhibited a combination of crushing with wedge splitting and crushing with compression and shearing parallel to the grain.

Design of selected wood species for longer span trusses

The trends of researches in the built industry are exploration of the available alternatives; either as raw materials or finished products construction materials, to most construction materials that have been playing dominant roles in construction industry for decades. Aside that the cost of using them in construction keep rising, the associated health hazards in their production and usage are huge and costly to rectify. The usage of locally available construction materials is being hindered by the lack of useful engineering data of the materials for structural design. Wood is an alternative local, green and sustainable material to steel in roof truss design and construction. Its usage has been limited to short span roof trusses based on inherited knowledge especially in Africa. There is need to know the actual capacity and potential of various wood species in relation to roof design. This work studied the properties of; Gmelina arborea, Tectona grandis (Teak), Terminalia superba (Afara), Ayin (Anogeissus leiocarpus), and Acacia (Robinia pseudoacacia). The values obtained from the laboratory experiments conducted on them were used to design rafter and tie beam of king post roof truss spanned to 12 m and 8 m using timber section 0f 50 mm x 150 mm of all the species. Then section sizes of 150 mm x 250 mm and 250 mm x 350 mm of Acacia were then designed separately. It was found that the five species were not suitable for long span roofing using the chosen three section sizes because the tie beams failed in deflection, which is most critical to deliver a safe, durable and serviceable roof. However, all the species, except Afara, are satisfactory for rafter whose span is not more than 7.5 m. It was also discovered that the higher the section size of timber used in the design the lower the deflection.

A Review of Shear Properties for Malaysian Tropical Timber in Structural Size

In recent years, the studies on producing data on physical and mechanical properties of Malaysian timber specimens have evolved from small clear specimen to structural size specimen, where most of the research method was based on the American Standard Testing Manual ASTM D198. Numerous data regarding mechanical properties on structural size specimen have been produced through this method, such as bending and compression test. Unfortunately, studies on shear properties on structural size timber are very scarce. It has reviewed that the global timber researchers are focusing to produce data on shear properties of European timber species such as Oak, Spruce and Pine where both shear strength and shear modulus data were obtained from bending and torsion test. Furthermore, from the review of the existing literature, it is clear that there is no proper studies focusing on development of shear properties of Malaysian tropical timber, especially torsion test in accordance with EN 408:2010. Therefore, the aim of this study is to investigate the shear properties (shear strength and shear modulus) of Malaysian Tropical Timber in large size.

Application of diameter distribution model for volume estimation in Tectona grandis L.f. stands in the Oluwa forest reserve, Nigeria

The ability to predict the distribution of diameters in a stand is essential for forest managers to make informed management decisions such as prescription of silvicultural treatments and harvesting regimes. Such information is preferably derived from suitable distribution model. This study evaluated the performance of four distribution models in describing the structure of the teak stands in Oluwa Forest Reserve, Nigeria. Data were collected from 12 temporary sample plots of 20 × 20 m size in the teak stand. Maximum likelihood estimator was used to fit the distribution models: beta, gamma, Johnson SB, and Weibull to the diameter data from the teak stand. Relative rank-sum derived from four indices was used to conclude on the most suitable distribution for the stand. The results showed that the Weibull distribution was the most suitable function for the teak stand with a relative rank-sum of 4.0. Application of Weibull distribution together with suitable height-diameter and volume models estimated yield of 136.281 m3 ha-1 within timber size class (diameter ≥30 cm). And a total of 309.640 m3 ha-1 was estimated for the stand. Other product specifications were also provided. This would help in the routine management of the stand.

Ágar e carvão ativado influenciam no desenvolvimento in vitro da parte aérea e radicular de sequoia

Plantios experimentais com Sequoia sempervirens (Lamb), espécie conhecida mundialmente pelo grande porte, longevidade e qualidade madeireira, estão iniciando no Brasil, tornando necessário a disponibilidade de mudas de qualidade. Assim, a técnica de cultura de tecidos, via micropropagação, se torna uma grande aliada pela garantia de superioridade genética, produção em grande escala e tempo reduzido de propagação. Atualmente há inúmeros protocolos para diversas espécies, porém, é necessário verificar todos os agentes influentes no sucesso do desenvolvimento in vitro. O objetivo deste trabalho foi determinar a influência do carvão ativado e de concentrações de ágar no desenvolvimento in vitro aéreo e de raízes de S. sempervirens. Os tratamentos realizados envolveram a presença/ausência do carvão ativado (1 g L-1), combinados com concentrações de ágar (4, 5 e 6 g L-1) em meio MS 50%. Para o número e comprimento de brotos e de raízes, apenas o carvão ativado foi significativo, sendo que a presença beneficiou o desenvolvimento dos explantes. Para porcentagem de calo, houve interação dos fatores, sendo que maiores concentrações de ágar (5 e 6 g L-1) na presença do carvão foram prejudiciais, pois apresentaram maior calosidade, o que minimiza as taxas de enraizamento. Indica-se a adição de carvão ativado (1 g L-1) e de menor concentração de ágar (4 g L-1) em meio de cultura MS 50% para um melhor desenvolvimento in vitro de sequoia.

Anthracological analyses of charcoal production sites at a high spatial resolution: the role of topography in the historical distribution of tree taxa in the northern Vosges mountains, France

The rising demand for charcoal from industrialization during the eighteenth century led to the establishment of a large number of charcoal production sites (CPSs) within the woodland ecosystems of Europe. The CPSs still present today can be investigated to assess the past woodland composition in terms of taxa present and timber size, at a high spatial resolution. The present study was done in the northern Vosges region in France, an area of low mountains covered by woods with some important past industrial sites in several of its valleys. We aimed to investigate the possible role of topographical variables such as altitude and aspect in the distribution of CPSs and in the past distribution of tree taxa. Charcoal production sites were found, identified and sampled in four valley catchment areas, and a numerical model of elevation was used to compute the topography of the landscape. A total of 233 sites were recorded and anthracological (charcoal) samples from 121 of these were analysed. The radiocarbon dates of 20 CPSs range between the late 17th and the early twentieth century AD, which corresponds to the peak of industrial activity in this region. The spatial distribution of CPSs appears to increase in density close to streams, and 14 tree taxa were identified in the charcoal records, with Fagus and Quercus being dominant by far. Our results revealed the strong influence of the direction in which the slope faced on the taxon composition of the anthracological spectra. These results suggest that the local woodland stands which were used to supply the charcoal kilns depended on the local environmental conditions. Furthermore, the composition of the woodland has changed significantly over time, with more Pinus sylvestris at present.

Determination of destructive forces in a rod-cable arch

The aim of research - comparison the results of the experimental data with the computer modeling the work of the strengthened brick-cable arch. Methods. Experimental and theoretical methods of research. Results. Firstly, the tests on a small desktop models were performed, for the determination the nature of destruction of the construction. During them, it was discovered, that the arch crash is taking place because of the splitting the small size timber bricks, or as the result of the breaking its steel strengthening elements. Further, the computer model of the construction was created with the help of physically and geometrically nonlinear finite elements at LIRA-SAPR PC. The generated model was load by a concentrated force at its top zone, the same one, as it had been during the experiments before. On the results of the calculation, the maximum deformation was received, which are different from the experimental one on a value less then 10%, what suggests the nearness the computer model to the real construction. The highest compressive strengths of the arch and the largest stretching forces of its steel bands were determined during the further analysis of the model. Maximum splitting and stretching forces also were calculated theoretically, according to the formulas of SP 64.13330.2017 and SP 20.13330.2016. It was determined that the timber bricks have more than 7 times reserve of strength, and the steel bands over them - only times, and during the growth of external force, the arch will crash because of its steel sprengel bands breakage. By the results of the research, the calculation algorithm of such kind constructions was generated, at the base of LIRA-SAPR PC. It was recommended first, to determine deformation of the strengthened brick-cable arch, with further checking the timber elements for splitting and steel sprengel elements for maximum permissible stretching. The problem of stability the flat form of deformation for the brickcable arch are the same as for the glued one, because of the tight connection the timber bricks, with elimination their exit from the frontal plane.

Comparison of techniques for quantification of internal stress within industrial kiln-dried timber

For a quantification of internal stress within industrial kiln-dried timber, a comparison of a new restoring force (RF) technique is made against the McMillen slice test and the standard case-hardening test. Simulation of the RF has been performed by using a numerical model of finite element (FE) analysis. 30 mm thick industrial kiln-dried rubberwood timber with 58, 78 and 100 mm widths was used in the study. The measured RFs for each timber size are proportional to the released strain data measured by the McMillan slice test and the gap openings measured according to the case-hardening test. The FE simulated and measured RFs are in good agreement. The geometrical shape factor as functions of timber width and cutting depth ratio is derived so that the internal stress can then be calculated without accounting for the modulus of elasticity. The calculated maximum internal stresses of all the examined timber sizes fall into a single curve and linearly relate to the released strain data. The RF measurement has the potential to be an alternative method to the existing techniques for a reliable and meaningful assessment of drying stress within industrial kiln-dried timber.

TENSILE BEHAVIOR OF BOLTED TIMBER COMPOSITE HALF-LAP CONNECTION FOR KERUING AND SESENDOK

Over recent years, half-lap connection is widely used all over the world to provide longer structural member due to limited size of sawn timber in construction industries. Timber connected in joints may reduce overall mechanical properties of the structure. This paper present finding on a series of connection of half lap bolted joint member from Keruing (SG5) and Sesendok (SG7) timber species. The half-lap connection were subjected to tensile test and reinforced with GFRP sheet that were conducted until failure to determine their tensile behavior. The results showed that the GFRP help to increase the load carrying capacity of all the timber specimens especially timber species that lies in a weak strength group for almost 30 % by strength.

Low frequency vibroacoustic investigation of wooden T-junctions

In this paper, an experimental investigation on the influence of glue on the low frequency vibroacoustic performance (up to 200Hz) of wooden T-junctions is presented along with a discussion of modelling issues related to the junctions. The mock-ups studied represent cut-outs of full size timber floor assemblies typically used in Sweden. Their dynamic performance was first studied experimentally by means of modal analysis. Moreover, finite element (FE) simulations of the T-junctions were carried out to establish reliable prediction tools, using the measurement data as calibration input. Modelling issues were addressed to investigate the influence of different features that must be taken into account when simulating the connections as part of larger structures. Guidelines for modelling these type of connections, when developing low frequency FE predictive tools, are presented here.

Investigation of Sawmill Management and Technology on Waste Reduction at Selected Sawmills in Moratuwa, Sri Lanka

The demand for sawn timber and wood-based products is rising steadily with new developments and the growing domestic consumption in Sri Lanka. Therefore, it is important to strike a balance between the increasing demand and consumption of forest resources. Thus, the key objective of this study was to investigate the effects of sawmill management and technological parameters on loss in conversion from logs to sawn timber and to compare the sawmill efficiency in private sawmills with the state timber corporation sawmill.Sawmill management and technological parameters were studied in 21 private sawmills and State Timber Corporation sawmill in Kaldemulla to evaluate the effects on loss in conversion. The selected sawmills represent all types available in Sri Lanka, i.e., frame saw, circular saw and band saw mills. Based on the results, mean percentage loss in conversion of teak and mahogany timber for all sawmills (private and State Timber Corporation) in Moratuwa found to be 53.10%. Significant differences were observed in loss in conversion values between the three categories of private sawmills as well as within sawmills of the same category. It was shown that loss in conversion values also varied with sawmill management and technological parameters such as type of machinery employed, sharpening frequency and sawyer’s experience, saw setting, availability of log alignment equipment and saw guards, oversizing and sawn timber sizes.

Innovative use of Reinforced Concrete for Sustainability of Purse Seine Boat Building in Aceh

Indonesia is an archipelago with only 30% landmass, hence inter-island transport and fisheries are important sectors. Boats used by fishermen and to transport goods as well as people across Indonesia's many islands are mainly small to medium sized timber boats of up to 30 gross weight tonnes (GWT). Large sized timber beams are needed for the boat keel and frames. However, since 2007 logging was banned in the Nanggroe Aceh Darusalam (NAD) region. This has resulted in scarcity and increased timber costs for conventional timber boat builders in the area. Hence other suitable substitute materials, in lieu of timber, should be explored to build fishermen's purse seine boats. In this study, we explore an innovative use of reinforced concrete as substitute for large size timber keel and boat hull frames of purse seine fishermen boats. As far as we are aware, this type of exploration study specific for purse seine boats in NAD is unprecedented. Our analysis indicates that using concrete frame provides better stability and adds to the boat's strength as well as extends its life use. Further, reinforced concrete can be a more cost efficient material to substitute for boat timber frame. Leaner reinforced concrete beams can be used compared to timber beams. The cost savings of using concrete for the boat frame in lieu of timber frame is estimated to be around 15%. Construction time to build a boat using reinforced concrete frame can be reduced by almost half compared to conventional timber frame boat of the same size. The findings of this exploratory study can contribute to enrich innovations in civil engineering construction, sustain the traditional purse seine boat building industry, and ultimately the livelihood of fishermen in NAD region. Findings can also be potentially further explored for application to other type of traditional timber boat construction for inter-island sea transportation services of goods and people in Indonesia, and perhaps also for other archipelago developing nations as well.

Influence of cross-section and knot assessment on the strength of visually graded Norway spruce

The strength of graded timber is determined by a multitude of parameters. Properties of interest are the shape of the cross-section and the wood quality. With regard to strength, wood quality is primarily expressed in terms of knots and knot clusters which, together with the cross-section of the timber, are used to calculate knot ratios. By applying the visual grading rules as given in the German standard DIN 4074-1, the influence of different timber sizes on grading results has been analysed. Different grading approaches for joists and boards exist and are taken into account in the assessment of 5,665 specimens originating from various parts of Europe. It was shown that both the cross-section and the grading method have a major influence on the characteristic strength values of Norway spruce. Limitations of the current standard with respect to its applicability to certain cross-sections are exposed. Alternative, simple grading approaches for boards are proposed. They ensure equal strength values and yields comparable to the rather complicated board rules used nowadays.

Timber Engineering Notebook No. 2: Engineered wood products and timber structural systems

There are limitations on the maximum cross-sectional size and lengths of sawn timber that can be used as a structural component due to the availability of log sizes and the presence of naturally occurring defects in the timber (see Timber Engineering Notebook No. 1). These defects can be cut out and the timber reconstituted using engineered wood techniques such as finger jointing to create longer lengths of timber of an assured strength grade, or laminating to form a homogeneous timber section. Combinations of timber or laminated sections with different materials such as wood-based boards or metal elements are used to create ‘engineered wood products' (EWPs) whose maximum size is limited only by manufacturing, handling and transportation constraints. In addition to engineered wood products, there are reconstituted board products which comprise smaller wood-based strands and fibres re-formed into panel products. These have structural applications but are also used extensively in the furniture-making and packaging industries. Types of timber structural systems and their applications are also introduced in this Notebook

Physical and Mechanical Properties of Loblolly and Slash Pine Wood from Uruguayan Plantations

Abstract The available wood supply in Uruguay comprises trees that grow so fast in intensively managed plantations that they reach saw timber size in 25 years or fewer. Trees harvested at this age contain high proportions of juvenile wood that may lead to lumber low in stiffness and strength. A project was conducted to characterize fast-growing wood, determine engineering properties, and assign visual structural grades of lumber. The present study evaluated properties of 15- and 25-year-old loblolly (Pinus taeda L.) and slash (Pinus elliottii Eng.) pine to better understand the current available locally produced wood material. A total of 175 stump bolts from trees from two commercial plantations provided inner and outer small clear specimens for property evaluation. Specific gravity, bending, compression parallel to grain and perpendicular to grain, and shear tests were conducted. Most properties significantly increased radially away from the pith. The outer wood appears to be denser, stiffer, and stronger than the inner wood in both plantations. Wood from 15-year-old San José trees showed significantly lower properties than 25-year-old Paysandú trees, and had considerably inferior properties compared with values listed in the Wood Handbook (US Department of Agriculture 1999). Our results on 25-year-old Paysandú small clear specimens showed properties similar to those of previous studies on small clear and structural size pieces. Therefore, it can be expected that lumber from 25-year-old Paysandú trees will eventually comply with required properties for structural use. A second on-going phase of this study addressing structural size specimens will help to establish more definite conclusions.

SAW MARKS IN VERNACULAR BUILDINGS AND THEIR WIDER SIGNIFICANCE

Surviving saw marks in timber-framed buildings can indicate whether the timbers were trestle-sawn or pit-sawn, although there is no general agreement about when the change from one to the other occurred. Evidence from tree-ring dated buildings shows that the change from trestle-sawing to pit-sawing in Herefordshire took place in and around 1540. This paper discusses the possible reasons for the change and how it may have influenced the size and quality of timber used after the middle of the sixteenth century.

Enhancing chestnut coppices: silvicultural management and socio-economic context.

Castanea sativa is one of the most important species for timber production in Italy but, both management system, ownership type and wood chain structure, aren’t able to enhance enough the market value of wood assortments. Although the high demand of quality timber, the internal production is heavily reduced, mainly as far as timber quality is concerned and because of the lack of suitable timber sizes. In this context, experimental trials have been approached to identify and verify which silvicultural methods are best suited to reach high yields depending to the investments needed and the local socio-economical condition. Two technical approaches were evaluated: stand silviculture and single-tree oriented silviculture. As for the socio-economical aspects, a few demographic indexes have been examined and the first-phase processing enterprises acting in the concerned area were analyzed. The goals of this paper are to evaluate the biological response to the applied silviculture, to analyze the problems arisen and to estimate the applicability of the proposed methods in relation to the different socio-economic contexts. The research has been carried out in Tuscany in two important forest areas - Monte Amiata and Colline Metallifere - in young chestnut coppices characterized by an homogeneous stand density and a good site index. The two examined districts showed some similarities but they have mainly highlighted important differences about the social structure and concerns and enterprises characteristics. The area of Monte Amiata is typified by a higher residents density then the Colline Metallifere but only 1/3 of the population is employed in the agro-forest sector. In addition, in the Monte Amiata district most concerns are sized less than 2 hectares and chestnut is the main forest species. On the contrary, in the Colline Metallifere the agro-forest sector (57% of workers) is one of the main sources of income for the local communities and medium-sized concerns are noteworthy present. Chestnut stands have here a marginal role, oaks are dominant and the prevailing assortment is firewood. From a silvicultural viewpoint, both the studied areas showed a quite good potentiality, suitable st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabella normale; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

Investments in Timberland and Softwood Timber as Parts of Portfolio Selection in the United States: A Cointegration Analysis and Capital Asset Pricing Model

Abstract In this article we investigated the financial performance of investments in timberland and timber and their correlations with nonforestry financial assets in the United States. Cointegration analysis and the capital asset pricing model were used to examine the long-run and short-run correlations with quarterly data from January 1992 to June 2006. The results of the cointegration analysis revealed that investment return on timberland tended to increase by 1.3% as Southern softwood stumpage price increased by 1%, indicating that a shift from pulpwood to sawtimber production might increase timber price and thus benefit timberland investment. The results also indicated that there were positive correlations between farmland return and Southern softwood stumpage price and between the stock market and timberland, indicating that treatments such as high-intensity site preparation might increase land quality and, hence, enlarge timber size and increase timber price. However, investors need to be cautious with the stock market because any change in the stock market has a potential effect on the timberland market. The results of the capital asset pricing model showed that timberland generated significant excess returns over the study period, but softwood timber did not. Timberland or softwood did not reduce systematic risk in a portfolio with stocks in the short run. In the short run, abnormal returns on timberland did occur, and timberland would be a desirable investment vehicle mixed with real estate.

Determination of shear modulus on construction size timber

Determination of shear modulus on construction size timber

Determination of shear modulus on construction size timber

Shear modulus determination of construction size timber was examined. Three different Techniques were used: torsional vibration, simultan E&G, and variation of span technique. We found that the simultan E&G technique is quite sensitive to the error of natural frequency determination and provides only an estimate for G. Better shear modulus determinations are the static and torsional techniques, but the torsional technique is most precise. The torsional vibration technique can be a good solution for shear modulus determination in an industrial environment because it provides quick and precise etermination, but standardization of the method would first be necessary. We found a high correlation coefficient (0.80) between the screw withdrawal resistance and shear modulus of 2 by 4 timber. Based on this result it is possible to estimate the shear modulus of timber even if the timber is installed in a structure.