Physical properties of wood
design of wood products. Some physical properties discussed and tabulated are influ-enced by species as well as variables like moisture content; other properties tend to be independent of species. The thor-oughness of sampling and the degree of variability influence the confidence with which species-dependent properties are lovedatingfind.com by: he physical properties of a wood species are those that affect its appearance, weight, feel, and smell. Most craftsmen aren’t especially concerned about feel and smell, since these change considerably when you apply a finish. But appearance is paramount. Weight can also be important if the project is meant to be moved or carried.
Wood is the oldest material used by humans for propeerties after stone masonry. Despite its complex chemical nature, wood has excellent properties which lend themselves to human use.
It is readily and economically available; easily machinable; amenable to fabrication zre an infinite variety of sizes and shapes using simple on-site building techniques. Following are some basic properties of wood:. However, it also has some drawbacks of which the user must be phgsical. Physical Properties Chemical Properties. Following properties of wood makes it good for use in construction.
Generally, specific gravity SG and the major strength properties of wood are directly how to check it refund status online. SG for the major, usually used structural species ranges from roughly 0.
Higher allowable design values are assigned to those pieces having narrower growth rings more rings per inch or more dense latewood per growth ring and, hence, higher SG. Wood is hygroscopic in nature. It picks up or gives off moisture to equalize with the relative humidity and temperature in the atmosphere. As it does so, it changes in strength. Wood also shrinks as it dries, or swells as it picks up moisture, with concomitant warpage potential.
Critical in this process is the fiber saturation physicak fsp. Seasoning of wood is performed before using in construction. There is no practical way to prevent moisture change in wood; most wood finishes and coatings only slow the process properhies. Thus, vapor barriers, adequate ventilation, exclusion of water from wood, or preservative treatment are absolutely essential in wood construction.
The combination of high relative humidity or MC and high temperatures, in un-ventilated attic areas, can have serious effects on roof sheathing materials and wre elements because of the potential for attack by decay organisms. Simple remedies and caution usually prevent any problems.
This characteristic, which is rarely encountered in normal construction, is an advantage in the manufacture of some reconstituted board products, where high temperatures and pressures are utilized. Timber is the most environmentally responsible building material.
Timber has low production energy requirements and is a net carbon absorber. Timber is a renewable resource. Well-managed forests produce timber on a how to order your college transcripts continuous skme, with minimal adverse effects on soil and water values. Timber is readily available. Australia has significant forest resources including a plantation estate covering more than 1.
Timber is strong, light and reliable making timber construction simpler and safer than steel or concrete construction. A comparison with od and concrete shows that oc pine structural timber, for example, has a strength for weight ratio 20 percent higher than structural steel and four to five times better than un-reinforced concrete in compression. The lightweight structures possible in wood confer flow-on advantages in terms of reduced foundation costs, reduced earthquake loading physiccal easier transport.
Building components and complete constructions are simple and safe to erect, and cheaper to deconstruct or reuse at the end of a building is useful life. Timber has low toxicity and therefore requires no special safety precautions to work with it, other than normal protection from dusts and splinters. Timber frame construction requires little in the way of heavy lifting equipment making building sites safer work places. Timber being how to make a long distance relationship work in college has obvious benefits in terms of electrical safety.
Modern timber construction has phsical fire resistance due to incombustible linings protecting light frames.
Increasingly specialist timber frame and truss manufacturers use high tech ;roperties enabling accurate and speedy installation. Recyclable - Timber is a forgiving material that can be easily disassembled and reworked. If demolition or deconstruction of a wooden building is necessary, many wood-based products can be recycled or reused. Timber trusses and frames, factory fabricated from sawn timber and toothed metal plate connectors, have come to dominate roof construction for small buildings such as houses and large industrial buildings where clear spans up to 50 metres are required.
Timber trusses compete with other roof structural systems on cost, high performance, versatility and ready availability, supported by design software packages supplied by the plate manufacturers to the fabricators. Comparative studies of the economics of different wall framing systems indicate that, in terms of direct building expenses, timber frames are consistently the most cost-effective solution.
There are many factors to consider when comparing the economics of different construction systems including the wiod of the layout, site, builder experience, and relative material prices at the time of building. However, comparative studies of the economics of different wall framing systems indicate that, in terms of direct building expenses, timber frames are consistently the most cost-effective solution.
In the medium to long term, the forecasts for the Australian wood supply indicate a stable and growing supply. This means that prices for framing timber are likely to be more stable for builders in the long term. However, this price stability is questionable for materials such as steel, which consume considerable amounts of fossil shat in their manufacture.
The smelting of steel is heavily reliant on the continued availability of cheap sources of fossil fuels, a scenario which is becoming highly uncertain in an increasingly energy and security conscious world. Properties of timber also include durability. Good detailing, physicl and maintenance ensure that oroperties structures last for lifetimes. Although many buildings become obsolete and are demolished long before the end of their natural lives, timber buildings correctly designed and maintained can have an what is a middle class income in canada life.
Propertes key to long life is protection from weather, insect attack and decay, through well-established design detailing, surface coating systems, selection of durable species, and preservative treatment processes. In all countries of the world, and Australia is no exception, historic timber buildings testify to these principles.
In termite-prone areas, how to change recessed light bulb on high ceiling buildings are vulnerable to termite attack of contents, so protection is needed regardless of construction materials. Protection systems rely on physical or chemical barriers, or both, and their effectiveness depends on the quality of the design, construction, inspection and what do pcv valves do. The risk of termite attack should whag assessed after consulting with local building authorities and an appropriate termite management system should be implemented.
The system may include physical or chemical barriers or in higher risk areas, a sme resistant treated timber or naturally termite resistant frame may also be spme.
In any case any management system should include regular inspection to ensure that barriers have not been breached. It is therefore critical that the system type and inspection schedule are understood by all future householders. Importantly, termites are an integral part of the ecology of Australia, however, with awareness, planning and using cost effective systems, they can be effectively managed.
Well-designed Timber structures are comfortable to live in all year round no matter where you are. Of the best properties of wood, flexibility of design forms and finishes is an most sought. This flexibility also extends to the ease with which existing buildings can be added to or modified to suit changing hwat.
User friendly versatile timber gives building designers creative freedom providing homeowners with flexible design choices. Timber is simply the best building material physifal builders, designers and homeowners and can zre used to construct the homes we love, structures we admire and warehouses, commercial buildings and other structures.
The timber frame method of building gives designers flexibility in both layout and external appearance. High levels of thermal insulation are incorporated within the construction, reducing heating costs and conserving energy.
An properries property of timber is that it should have adequate compression strength to wbat used for different purposes in construction industry. Though, would is chemically inert as compared to other materials but is affected by some acids and bases. Some species have proven very useful for food containers berry boxes and crates because they are nontoxic and impart no taste to the foods contained therein. Wood structures have also found widespread use as storage facilities for salt and fertilizer chemicals.
Chemical Properties of Wood Chemical Propertiies on Timber Though, would is chemically inert as compared to other materials but is affected by some acids and bases.
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Physical properties of wood
Presents properties of wood and wood-based products of particular concern to the architect and engineer. Includes discussion of designing with wood and wood-based products along with some pertinent uses. Keywords: wood structure, physical properties (wood), mechanical properties (wood), lumber, wood-based. PHYSICAL PROPERTIES OF WOOD Physical properties describe the quantitative characteristics of wood and its behavior to external influences other than applied forces. Included are such properties as moisture content, density, dimensional stability, thermal and pyrolytic (fire) properties, natural durability, and chemical lovedatingfind.com Size: KB. The physical and mechanical properties of wood are important factors used in determining the suitability and application of wood material, these in turn depends on the wood specie. This study was conducted to determine the effect of wood species on some physical properties .
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material — a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees,  or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs.
It also conveys water and nutrients between the leaves , other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber. Wood has been used for thousands of years for fuel , as a construction material , for making tools and weapons , furniture and paper. More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
In approximately 3. Dominant uses were for furniture and building construction. A discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately to million years ago. Wood can be dated by carbon dating and in some species by dendrochronology to determine when a wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses , tools , weapons , furniture , packaging , artworks , and paper.
Known constructions using wood date back ten thousand years. Buildings like the European Neolithic long house were made primarily of wood. Recent use of wood has been enhanced by the addition of steel and bronze into construction. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut. Wood, in the strict sense, is yielded by trees , which increase in diameter by the formation, between the existing wood and the inner bark , of new woody layers which envelop the entire stem, living branches, and roots.
This process is known as secondary growth ; it is the result of cell division in the vascular cambium , a lateral meristem, and subsequent expansion of the new cells. These cells then go on to form thickened secondary cell walls, composed mainly of cellulose , hemicellulose and lignin. Where the differences between the four seasons are distinct, e. New Zealand , growth can occur in a discrete annual or seasonal pattern, leading to growth rings ; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces.
If the distinctiveness between seasons is annual as is the case in equatorial regions, e. Singapore , these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will likely be deformed as the plant overgrows the scar. If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements.
It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood. If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline.
The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider.
As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings.
In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks , maintain the same width of ring for hundreds of years.
Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases. As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot.
The dead branch may not be attached to the trunk wood except at its base, and can drop out after the tree has been sawn into boards.
Knots affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along the wood grain, [ citation needed ] but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" usually darker piece of wood around which the grain of the rest of the wood "flows" parts and rejoins.
Within a knot, the direction of the wood grain direction is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a side branch or a dormant bud. A knot when the base of a side branch is conical in shape hence the roughly circular cross-section with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.
In grading lumber and structural timber , knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.
Knots materially affect cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength is an important consideration.
The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots, however, may be located along the neutral plane of a beam and increase the strength by preventing longitudinal shearing.
Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects. Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location.
Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain. In some decorative applications, wood with knots may be desirable to add visual interest.
In applications where wood is painted , such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution knotting , correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.
Heartwood or duramen  is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously. Some uncertainty exists as to whether the wood dies during heartwood formation, as it can still chemically react to decay organisms, but only once. The term heartwood derives solely from its position and not from any vital importance to the tree.
This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut , black locust , mulberry , osage-orange , and sassafras , while in maple , ash , hickory , hackberry , beech , and pine, thick sapwood is the rule.
Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion.
Sapwood or alburnum  is the younger, outermost wood; in the growing tree it is living wood,  and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves.
However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead.
All wood in a tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees of species that do form heartwood grown in the open may become of considerable size, 30 cm 12 in or more in diameter, before any heartwood begins to form, for example, in second-growth hickory , or open-grown pines.
No definite relation exists between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is relatively thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.
When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots.
No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.
Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies.
This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness , strength , and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true. In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous see section of yew log above.
This is produced by deposits in the heartwood of chemical substances, so that a dramatic color variation does not imply a significant difference in the mechanical properties of heartwood and sapwood, although there may be a marked biochemical difference between the two. Some experiments on very resinous longleaf pine specimens indicate an increase in strength, due to the resin which increases the strength when dry.
Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites ; however they are very flammable.
Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut.
Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.