5. Timber Application, Products and their use

Transcription

1 TIMBER 5. Timber Application, Products and their use Lecturer: Prof. Dr. Mohammad Ismail Faculty of Civil Engineering, -Skudai, Johor Darul Ta zim, MALAYSIA 1 Room : C Tel : December 6, 2013

2 2 STRUCTURAL APPLICATION Marine Work Timber use for wharves, piers, sheet piling and cofferdam even though many of these application has been replaced by steel For groynes still economic to use timber Problem associated with marine work Impact, Abrasion, Infestation by marine borers Fungal attack, Erosion by chemical action or salt Wave action, Dimensional movement caused by differential temperature Properties Required High density, closeness of grain and resistance to impact, natural durability and wear resistance Department of Structures and Materials

3 Heavy Construction Work Timber still used for heavy constructional purposes where availability and cost of materials are favourable. Among others Pylons, Gantries, Bridges, Shoring and abutments JSB Main Problem Impact or accidental loading, infestation, chemical and fungal attack, dimensional movement Properties Required High density, closeness of grain and resistance to impact, resistance to acidity, alkalinity and others 3 Department of Structures and Materials

4 Medium/Light Construction Work Roof trusses, partitions, screens, floors and wall panels JSB Main Problem Resistance to insect and fungal attack, minimum dimensional change Properties Required Reinforced any resistance to fire or rate of flame 4 Department of Structures and Materials

5 Drawback of Solid timber Inherent anisotropy Many natural defects Limited size in (section and length) Difficulty of drying 5

6 SHEET MATERIALS Range of sheet, board or panel products includes veneer and core plywoods, chipboard and flakeboards and a variety of fibreboards VERNEER PLYWOOD Correct name for plywood defined in BS 6566: Part 2 All the plies are made of veneers oriented with their plane parallel to the surface of the panel 6

7 Direction of the verneer grain in a ply is at right angles to the direction in the immediately adjacent plies There are odd number of plies The glues used depend on the intended use of the plywood, urea formaldehyde for interior and phenol formaldehyde for exterior 7

8 VERNEER PLYWOOD Initial cold press may be used before the assembly is put into a hot press, where the glue cures Cured panels cooled and trimmed to finished size Verneer plywood is generally graded in terms of appearance, durability and bond. According to MS 3.22, 1974, plywood graded to 1, 2 and 3 Local timber used for plywood: Kayu Kapur, Keruing, Mengkulang, Meranti dan Mersawa Size (L) 1.8m, 2.4, 2.7 and 3. (W) 600mm, 900 and 1.2m. (T) mm 8

9 CORE PLYWOOD Commonly referred to as blockboard or laminboard Manufactured from strips of solid timber, normally eachglued together to form a solid slab of material Normally used in interior applications and have only limited application in construction such as panelling, partitions and door blank 9

10 PARTICLEBOARDS Commonly referred to wood chipboard or recently oriented strand board (OSB) and cement bonded particle board 10

11 Chipboard Raw material may be solid wood, such as sawmill offcuts, forest thinnings or logging waste or wood residues such as planer shavings or sawdust Solid wood is fed into a chipper which cuts the required sizes and shape of particle The chips are then mixed with resin, usually urea formaldehyde and then formed into a mat on a flat plate, the oriented totally at random 11

12 Oriented strand board Development of waferboard made by cutting small roundwood logs or plywood peeler cores into large flakes which are less than 1 mm thickness OSB the flakes are trimmed into rectangular pieces at least twice as long as they are broad, length 75mm or more Manufacturing process nearly similar to chipboard Application - similar to plywood (wall sheathing) except in highly stressed zones 12

13 Cement bonded particleboards Small particles of wood blended with cement, water and chemical admixtures Wet mixture is then spread to thickness and held in a light press until the cement sets Cement bonded, wood content quite low Density much higher High resistance to fire Further information in BS

14 FIBREBOARDS Wood tissue reduced to the basic fiber, eliminate all trace of structure, defect and anistropy The product has exceptionally fine texture throughout, with very smooth surface finish According to BS 1142, fiberboard not normally use for structural purpose but for internal fitting and finishing and insulation Marketed as a replacement for solid timber mouldings in finishing joinery since its fine texture makes it readily machinable to a range of profiles Its smooth surface gives an excellent substrate for painting and it is more stable in changing environments 14

15 GLUED LAMINATED SECTION Glulam, or glue-laminated timber, introduced in Europe in the late nineteenth century, consists of sawn timber laminations bonded with an adhesive so that the grain of all laminations runs parallel with the long direction BS 4978 for softwood and BS 5756 for tropical hardwood 15

16 Glulam, or glue-laminated timber, introduced in Europe in the late nineteenth century, Consists of sawn timber laminations bonded with an adhesive so that the grain of all laminations runs parallel with the long direction 16

17 Lamination thickness may vary from 10 mm 50 mm Thinner lamination enabling tighter bends to be produced and giving greater strength Timber sections are kiln dried to a moisture content of about 12%, after which they are finger jointed to a required lengths 17

18 Manufactured in various sizes and shapes; curved, tapered circular, and spiralshaped members 18 Glulam is stronger in longitudinal direction and weaker in the tranverse direction

19 Advantage: flexibility of shape and size straight, curved, atches or frame and enabling clear spans in excess of 50m. Appearance warm and attractive Predictable in fire as solid timber. Additional protection in fire may be obtained by surface treatments, such as clear intumescent varnishes 19

20 Allowable strength properties superior than those of sawn timber Commonly used for purlins, joists, headers, beams, and truss members. Also in the design of pedestrian and highway bridges 20

21 1. Define fiber saturation point and equilibrium moisture content 2. Explain the effects of moisture content on the strength characteristics of wood 3. What is clear wood 4. Explain the decay and destruction of wood 5. Define growth ring, check, grain and slope grain 6. Explain seasoning and treatment of timber 21

22 JSB 22 Terima kasih