Influence of wood moisture content on modulus of elasticity on tension paralllel to the grain of brasilian species

Periodically, when necessary, standard documents are revised in order to analyze inconsistencies and to include considerations according new realities verified. In this sense, aiming to quantify the wood moisture content influence on modulus of elasticity, it was applied tension tests parallel to the grain for six specimens of different strength classes of wood, considering nominal moisture of 12, 20, 25, and 30% in Brazil. The present paper examine the adequacy of the current Brazilian standard ABNT NBR7190:1997, in review, about the adoption of a first degree equation to describe the influence of wood moisture content for timber structures design. It was obtained a new first degree equation which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, as recommendations it could be maintain the current expression for the next text of the referred document review, without prejudice to statistical significance of the estimates.

Análise das propriedades da madeira de estrutura de telhado após a ocorrência de um incêndio

The present study evaluated the mechanical properties of pieces of wood coming from the roof structure of a residence subject fire in the rural area of Itapeva/SP. The structure was built 25 years ago using wooden beams of the species Guarucaia (Peltophorum vogelianum), where the specimens were removed. The research methodology included qualitative evaluation of the samples, estimating the layer pyrolysis and carbonization of the wood, measuring of density and mechanical tests of compression parallel to grain, tension parallel to grain and shear. The mechanical properties of wood were analytically correlated with the layers carbonization and pyrolysis that are influenced by the temperature and time of fire; these values were estimated at 1000 °C and two hours for the case in question. The results indicate that the strength properties of degraded wood are different from a healthy wood. The level of thermodegradation, in general, can be measured by density, result in weight loss due to decomposition of the wooden components.

Análise da estabilidade dimensional e resistência mecânica em bambu Guadua angustifolia pós-processos de tratamentos químicos e térmico

Nowadays, bamboo is being studied because of their strength properties according with their specific mass and speed of growth, which makes it an important alternative as a new resource that will help reduce pressure on forests and helpping them favoring the minimization of uncontrolled deforestation in many regions of Brazil. This study aimed, in general, to analyze physical and mechanical properties of the material with the divulgation of its potential for industrial application. To do so, in this research were determined in relation to the physical properties, moisture content, dimensional stability and the apparent densities and the mechanics and basic, just a tension parallel to grain, in order to observe the interference of various kinds of treatments (chemical, thermal and natural) on the strength and modulus of elasticity in this request. The species used was the Guadua angustifolia, a species native of Brazil. All tests were performed at Universidade Estadual Paulista - Campus Experimental Itapeva in the laboratory of Materials Properties. The methodology used for testing of moisture, density and tension parallel to grain were based on NBR 7190/1997 for the wood, and dimensional stability tests were based on much the same as in COPANT 462/1972 (South American) . The preservative treatments conducted followed the recommendation of each manufacturer. The values obtained in tests of physical properties were satisfactory especially with respect to density and dimensional stability analyzed by the coefficient of anisotropy, showed that, compared to wood, excellent quality for the shrinkage test, obtaining a coefficient of 1.2. With respect to parallel tensile tests to fibre results showed, in most cases, that test specimens with the presence of us have lower values of resistance and modulus of elasticity when compared with those without us. In the treatment of thermal-treatment there was an apparent treatment there was an apparent increase in...

Estudo de compósitos de madeira com reforço em bambu para utilização em mobiliário

Bamboo has been studied because of its peculiar mechanical properties and numerous possibilities of use, besides being a fast-growing grass and short cutting cycle. This study aimed to analyze the mechanical characteristics of wood-bamboo composite material, where the samples were developed from the combination of layers of bamboo as a structural reinforcement in solid pieces of pine and EGP panel parts. The species of wood used was Pinus taeda, and the bamboo species Guadua angustifolia and Dendrocalamus giganteus. All work was conducted at the Universidade Estadual Paulista - UNESP in the laboratory of Physical and Mechanical Properties of Wood. Tests including the density and tension parallel to grain of the bamboo species used and the static bending of composites in order to use this in the furniture industry. For the tests have been used as a basis the requirements of the normative document NBR 7190/97. The values obtained in the tests showed a significant increase in strength and stiffness compared to unreinforced parts, where there was an increase in MOE and MOR in static bending in all specimens used in evidence. The results showed the possibility of reducing sections in furniture components and the possibility of improving the mechanical properties of parts with defects found in wood of Pinus Itapeva region of São Paulo

Evaluation of longitudinal modulus of elasticity in wood species for structural application

1024x768 This research aimed to investigate possible differences in values of longitudinal modulus of elasticity for wood species usually employed for structural purposes, as Castanheira (Bertholletia excelsa), Cambará (Erisma uncinatum), Cumaru (Dipteryx odorata), Jatobá (Hymenaea stilbocarpa), Garapa (Apuleia leiocarpa) and Peroba Rosa (Aspidosperma polyneuron), obtained from compression and tension parallel to grain, and static bending tests. Recommendations of the Brazilian standard ABNT NBR 7190:1997, Annex B, were followed. Statistical analysis results for the cited properties, had equivalent averages for the six wood species analyzed. This confirms that any of the three tests can be used to obtain the longitudinal elastic modulus and which could avoid the necessity of evaluating stiffness values for wood by more than one kind of mechanical test. Normal 0 21 false false false PT-BR X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat: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:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Influence of moisture content in some mechanical properties of two brazilian tropical wood species

This study aimed, with the aid of analysis of variance (ANOVA), to investigate and quantify the influence of moisture ranging between 12% and over 30% (fiber saturation) on the mechanical properties: strength and modulus of elasticity in compression and in tension parallel to grain; modulus of rupture and modulus of elasticity in static bending; shear strength parallel to grain considering wood species Ipê (Tabebuia sp) and Angelim Araroba (Vataireopsis araroba). Tests were performed according to the assumptions and calculating methods Brazilian standard ABNT NBR 7190, Anexx B, totalizing 400 tests. Results of ANOVA revealed a significant reduction (16% on average) for mechanical properties wood due to the increase in moisture content from 12% to over 30% (fiber saturation). The same behavior also occurred when assembly containing the two species was considered.

Behaviour of joints with bonded-in steel bars loaded parallel to the grain of timber elements

Within the sustainability context, this paper is extremely timely and relevant. The research focuses on broadening the use of timber structurally. The insight gained forms the basis for sustainable, fire resistant, economic and aesthetically pleasing moment resistant connections in timber.

Pull-out behaviour of axially loaded basalt fibre reinforced polymer (BFRP) rods bonded parallel to the grain of glulam elements

Synopsis: Bonded-in rod timber joints off er several advantages over conventional types of joint, including high local force transfer, very stiff connections, and improved ?re and aesthetic properties since the connection is completely hidden in the insulating timber members. More recently, the use of ?bre reinforced polymer (FRP) as a connecting rod, alternative to steel rods, in bonded-in rod connections for timber structures has been investigated. However, the investigation into the behaviour of such joints is limited, in particular, connections involving basalt ?bre reinforced polymers (BFRP) bars - which is the primary focus of this research. This paper presents an experimental programme conducted to investigate the behaviour of bonded-in BFRP bars loaded parallel to the grain of glulam members. Tensile pull-out tests were conducted to examine the effect of bonded length and bond stress-slip on the structural capacity of the connection. An analytical design expression for predicting pull-out capacity is proposed and the results have been compared with some established design equations. It was found that pull-out load increased approximately linearly with the bonded length, up to maximum which occurred at a bonded length of 15 times the hole diameter, and did not increase beyond this bonded length. The most signi?cant failure modes were failure at the timber/adhesive interface followed by pullout of the BFRP rod. Increased bonded lengths resulted in higher bond slip values compared to lower equivalent bonded lengths. The proposed design model gave the best predictions of pull-out capacity compared with other existing models.

Influence of embedded length on strength of BFRP rods bonded parallel to the grain in low grade timber by pullout-bending tests

Bonded-in rod connections in timber possess many desirable attributes in terms of efficiency, manufacture, performance, aesthetics and cost. In recent years research has been conducted on such connections using fibre reinforced polymers (FRPs) as an alternative to steel. This research programme investigates the pull-out capacity of Basalt FRP rods bonded-in in low grade Irish Sitka Spruce. Embedded length is thought to be the most influential variable contributing to pull- out capacity of bonded-in rods after rod diameter. Previous work has established an optimum embedded length of 15 times the hole diameter. However, this work only considered the effects of axial stress on the bond using a pull-compression testing system which may have given an artificially high pull out capacity as bending effects were neglected. A hinge system was utilised that allows the effects of bending force to be taken in to consideration along with axial forces in a pull-out test. This paper describes an experimental programme where such pull-bending tests were carried out on samples constructed of 12mm diameter BFRP bars with a 2mm glueline thickness and embedded lengths between 80mm and 280mm bonded-in to low-grade timber with an epoxy resin. Nine repetitions of each were tested. A clear increase in pull-out strength was found with increasing embedded length.

Influence of Wood Moisture Content on the Modulus of Elasticity in Compression Parallel to the Grain

Brazilian Standard ABNT NBR7190:1997 for timber structures design, adopts a first degree equation to describe the influence of wood moisture content. Periodically, when necessary, the referred standard is revised in order to analyze inconsistencies and to adopt considerations according new realities verified. So, the present paper aims to examine the adequacy of its equation which corrects to 12% of moisture the values of rigidity properties obtained on experimental tests. To quantify the moisture influence on modulus of elasticity, it was applied tests of compression parallel to the grain for six specimens of different strength classes, considering nominal moisture of 12; 20; 25; 30%. As results, modulus of elasticity in the moisture range 25-30% showed statistically equivalents, and was obtained a first degree equation to correlate the studied variables which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, it was indicated to maintain the current expression for the next text of the referred document review, without prejudice to statistical significance of the estimates.

A lesson in tension yet to be taut : a review

NOBEL prize-winning British writer Harold Pinter is best known for his social commentaries and for dark, sometimes violent "comedies of menace" that capture the cruelty at the heart of human relationships. It has been a while since a Pinter play was on the Brisbane stage, and it is exciting to see one of his lesser known early works, Betrayal, as part of Queensland Theatre Company's session. Betrayal moves backwards from a potentially scandalous moment. In a pub one night, Emma tells Jerry that his best friend Robert is divorcing her. Robert has been unfaithful. And, what's more, Robert now knows about their lengthy affair. What follows is a series of scenes that look back at the stages of that affair and the secrets that have lain unspoken at the heart of their comfortable middle-class lives for so long. Betrayal is characterised by the sparsity of action and language, dark humour, and sudden outbreaks of seemingly excessive cruelty that are a trademark of Pinter's writing for the theatre.

Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview

In dryland agricultural systems of the subtropical, semi-arid region of north-eastern Australia, water is the most limiting resource. Crop productivity depends on the efficient use of rainfall and available water stored in the soil during fallow. Agronomic management practices including a period of fallow, stubble retention, and reduced tillage enhance reserves of soil water. However, access to stored water in these soils may be restricted by the presence of growth-limiting conditions in the rooting zone of the crop. These have been termed as subsoil constraints. Subsoil constraints may include compacted or gravel layers (physical), sodicity, salinity, acidity, nutrient deficiencies, presence of toxic elements (chemical) and low microbial activity (biological). Several of these constraints may occur together in some soils. Farmers have often not been able to obtain the potential yield determined by their prevailing climatic conditions in the marginal rainfall areas of the northern grains region. In the past, the adoption of soil management practices had been largely restricted to the top 100 mm soil layer. Exploitation of the subsoil as a source of water and nutrients has largely been overlooked. The key towards realising potential yields would be to gain better understanding of subsoils and their limitations, then develop options to manage them practically and economically. Due to the complex nature of the causal factors of these constraints, efforts are required for a combination of management approaches rather than individual options, with the aim to combat these constraints for sustainable crop production, managing natural resources and avoiding environmental damage.

Graze to grain - measuring and modelling the effects of grazed pasture leys on soil nitrogen and sorghum yield on a Vertosol soil in the Australian subtropics

Highly productive sown pasture systems can result in high growth rates of beef cattle and lead to increases in soil nitrogen and the production of subsequent crops. The nitrogen dynamics and growth of grain sorghum following grazed annual legume leys or a grass pasture were investigated in a no-till system in the South Burnett district of Queensland. Two years of the tropical legumes Macrotyloma daltonii and Vigna trilobata (both self regenerating annual legumes) and Lablab purpureus (a resown annual legume) resulted in soil nitrate N (0-0.9 m depth), at sorghum sowing, ranging from 35 to 86 kg/ha compared with 4 kg/ha after pure grass pastures. Average grain sorghum production in the 4 cropping seasons following the grazed legume leys ranged from 2651 to 4012 kg/ha. Following the grass pasture, grain sorghum production in the first and second year was < 1900 kg/ha and by the third year grain yield was comparable to the legume systems. Simulation studies utilising the farming systems model APSIM indicated that the soil N and water dynamics following 2-year ley phases could be closely represented over 4 years and the prediction of sorghum growth during this time was reasonable. In simulated unfertilised sorghum crops grown from 1954 to 2004, grain yield did not exceed 1500 kg/ha in 50% of seasons following a grass pasture, while following 2-year legume leys, grain exceeded 3000 kg/ha in 80% of seasons. It was concluded that mixed farming systems that utilise short term legume-based pastures for beef production in rotation with crop production enterprises can be highly productive.

Can feral pig harvesting and co-ordinated control reduce damage to grain crops?

Commercial and recreational harvesting of pigs is often encouraged by pest managers because it is essentially a ‘free’ reduction in pest density. However, the reduction in numbers may provide minimal damage mitigation and may be inappropriately allocated in space and time. Additionally, more effective control (e.g. baiting) may not occur because of the incorrect perception that harvesting is effective or because pigs are valued for recreational use.