Unprotected timber exposed to the weather will discolour and may develop mould growth. Factors to consider Timber is an integral material to many of our products, especially seating. There are many structural and nonstructural applications of timber in building construction. DEFINITION The mechanical properties of wood are its fitness and ability to resist applied or external forces The mechanical properties of wood considered are (1) stiffness and elasticity, (2) tensile strength, (3) compressive or crushing strength, (4) shearing strength, (5) transverse or bending strength, (6) toughness, (7) hardness, (8) cleavability, (9) resilience. Watch the Video Below for more Information. This type of structure is called “cross-grained.”. Knots in the pine decrease the strength of the timber. Most trees are characterized by a typical color and odor.Thus, walnut wood is distinguished by its typical dark brown color.Similarly, a freshly cut teak wood has a golden yellow shade.The softwoods like deodar and pine show light (white) colors.As regards odor (smell), quite a few kind of woods are immediately identified by their characteristic smell.Teak kinds of wood have an aromatic smell.The pines smell of resi… Conversely, when dry wood is wetted the water is first received by the cell walls. A so-called ‘stable’ timber is the one that exhibits comparatively small dimensional changes in passing from the 90% to the 60% humidity conditions. Theodolite Parts and Functions [A Detailed Guide]. For construction purposes, the physical properties of the wood itself are most pertinent and European oak possesses a number of strengths that make it particularly desirable. Its Types, Parts Used in Construction. Hence, its quantity has to be reduced to the lowest possible limits by natural (seasoning) or artificial (drying) methods. On drying, the wood undergoes a shrinkage. Formwork (Shuttering) for Concrete [Its Types, Design]. Colour: It should be uniform. 3. It is known that in the drying process, moisture from the wood is lost first from the cell cavity and then from the cell walls. When cutting and exposed to the atmosphere, a balance may be achieved between the moisture in the atmosphere (humidity) and the wood. As regards odor (smell), quite a few kind of woods are immediately identified by their characteristic smell. It is because in the latter case “full width” of the cell walls is involved. The specimens are subjected to saturated steam at atmospheric pressure for a period of not less than 45 minutes before bending. admin, Information about the author you selected, link to author http://www.civilengineeringx.com, Number of articles by this author, 2011, Cost Effective Construction Techniques In Mass Housing Schemes, The Building Team-Managing the Building Process, Heating, Ventilation, and Air Conditioning, Plumbing—Water-Supply, Sprinkler, and Wastewater Systems, Assessment of Seismic Hazard of Territory, Understanding the Multidimensionality of the Phenomena, Full-Wave Ground Motion Forecast for Southern California, Seismic Performance and Simulation of Behavior of Structures, Bridge Embankments – Seismic Risk Assessment and Ranking, Dynamic Behaviour of the Confederation Bridge Under Seismic Loads, Weight, Mass, and Volume Relationships of soil, Payment arrangements, risks and project cost estimating, The development of construction procedures, Contract conditions used for civil engineering work, Properties of Structural Steels and Effects of Steelmaking and Fabrication, Building Design and Construction Handbook, Durability of concrete and cement composites. All woods are porous to some extent. It should not clog the saw. The direction and structure of the cells also effects the strength of the timber, straight grained timber is stronger than a cross grained or wavy timber. Most trees are characterized by a typical color and odor. The natural moisture content, Mc, of wood is easily determined from the below relationship. Some varieties may be as light as 0.3 whereas, in other varieties of timber, the specific gravity may approach 0.9. Timber compares favourably with other construction materials in terms of fire resistance. What is Scaffolding? Fire Resistance. Workability: Timber should be easily workable. Hence, the Strength of wood is determined with reference to the direction of the grain of the wood under load. Straight-grained timber is considered best, other things being the same. That level of moisture content of timber is called “equilibrium moisture content.”. It may vary from 300 to 900 km/cm2 or more. sibeliustalo23auerniitty_web.jpg. admin. Qualities of Good Timber. 3. Wood is a light material, so as such its sound insulation performance is not particularly good. Deformation is caused by the board cut from timber due to shrinkage and swelling. Thermal Properties. Analysis of Mechanical Properties of Cross-laminated Timber (CLT) with Plywood using Korean Larch. The properties of Timber Here at Forest we put a lot of care and attention into the manufacture of our products and we want you to enjoy them for many years to come. The color and odor, however, may show variation. 3. This lesson covers the physical and mechanicalproperties of wood. 8. Civil Engineering | Sometimes the fibers do not grow essentially parallel to the trunk. One of the most noticeable properties of wood is that it is a hygroscopic material, meaning that it tends to absorb moisture from the air depending on the humidity of its surroundings. The quality can be ensured by investigating the properties of timber. Design values for structural glued laminated soft wood timber for member stressed primarily in … Color and odor, specific gravity, moisture content, grain, shrinkage and swelling, and strength are the important characters which determine the properties of wood and timber. Density: Higher the density stronger is the timber. Before you use timber, you should know its properties. Structural Lumber - Properties - Properties of structural lumber Timber - Structural Lumber Section Sizes - Basic size, area, moments of inertia and section modulus for timber - metric units Wood - Moisture and Compressive Strength - Red Spruce, Longleaf Pine and Douglas Fir - moisture content and their compressive strength There is a variation of color from one tree to the other. Grains: In good timber grains are close. Hardness. The element connections are impervious to gas and smoke and the fire cannot spread. Academia.edu is a platform for academics to share research papers. Texture: Texture of good timber is fine and even. The CLT module acts like a capsule in the case of fire. It has a natural beauty and warmth and will change its appearance over time as it is subjected to the elements in outdoor situations. In the radial direction, it is of an intermediate order. WELL RESEARCHED ARTICLE AND HIGHLY INFORMATIVE ARTICLE ON WOOD, Highly informative in simple manner. The air seasoned woods can be made to lose further moisture by prolonged exposure (up to four years). The fibers may be very tightly and closely packed giving rise to a fine-grained texture in wood. 7. Timber is naturally an insulating material that creates a barrier between heat and cold. When trees are cut and laid to exposed conditions of the atmosphere. Chul Choi, a Erina Kojima, b Kyung-Jung Kim, a Mariko Yamasaki, b Yasutoshi Sasaki, b and Seog-Goo Kang a, * The bending strength of hybrid wooden-core laminated timber (HWLT), a composite material made from existing cross-laminated timber (CLT) and plywood, was analyzed. Density: Higher the density stronger is the timber. Grain signifies arrangement and direction of fibers and vessels in the wood: parallel to the trunk, oblique to the trunk or turned and twisted with respect to the longitudinal direction of growth. Thus, dark brown color is typical in walnuts, golden yellow is characteristic of fresh teak wood, and the creamish white color is found in softwoods like deodar. A laboratory test was carried out to develop the physical and mechanical properties (four-point bending test) of the timber species in accordance with EN 13153-1, ASTM D143 and EN 408. As such, wood may absorb moisture more than 2 to 2.5 times than its own weight. Hence, Mc values of natural (green) wood may sometimes be as high as 250 percent. Thermal Properties/Temperature Effects: Although wood is an excellent heat insulator, its strength and other properties are affected adversely by exposure for extended periods to … Abrasion: Good timber do not deteriorate due to wear. The deviation or the slope in grain from the straight alignment that may be due to disturbing conditions during the growth of the tree is considered a natural defect for construction purpose because many properties of timber are related to the grain. are indicated for each timber. They tend to reduce the strength indirectly. Similarly, dry wood on getting rain melted or wetted may undergo considerable swelling. Author Gravatar is shown here. capabilities of cross-laminated timber. You’ll learn in details about the Properties of Wood and Timbers here. Classification of timbers according to their steam-bending properties is however; based mainly on minimum bending radius of sound, clear specimens 1 in. Strength: Timber should have high strength in bending, shear and direct compression. Structural grading is the process by which timber is sorted into groups - or stress grades - with ideally, similar structural properties in each group. Similarly, hardwoods are always denser than soft woods as a whole. Warping: Good timber do not warp under changing environmental conditions. COMPRESSIVE STRENGTH: Timber from most of the trees is amazingly strong under compressive loads -500 kg/cm2 to 700 kg/cm2. The quality of timber must be ensured before using it for a purpose. Hardness and strength of wood depend to a great extent on its density. Thus, the tensile strength of some woods ranges from 500-2000 kg/cm2 parallel to the grain, whereas same values lie between 10-100 kg/cm2 for the same varieties when tested perpendicular to the grain. It is essential to clarify the terminology for its various uses. Timber is strong, light and reliable making timber construction simpler and safer than steel or concrete construction. Density: Higher the density of timber, greater will be its strength. Civil engineering training education, building construction, Author Gravatar is shown here. Soundness: A clear ringing sound when struck indicates the timber is good. Texture: Texture of good timber is fine and even. Here we have discussed both physical and mechanical properties of timber which affects timber quality. Cross-laminated timber burns at a rate of 0.67mm per minute and therefore the duration of the fire can be exactly calculated. Properties of Timber. Woods shows a good deal of variation in their Specific gravity. Defects like cracks, decay or a knot will decrease the strength of the timber. In a normal wood, the tracheids and vessels (called collectively as fibers) grow parallel to the length of the tree trunk. 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