Engg. wood

building material

1. ENGINEERED WOOD BUILDING MATERIAL

2. ENGINEERED WOOd Introduction Engineered wood, also called composite wood, man-made wood, or processed wood includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibers ,  veneers  or blocks of wood, together with adhesives, to form composite material ENGINEERED WOOD PRODUCTS Wood based products (usually composites) designed to meet application-specific performance requirements and to take best advantage of the structural properties of the different components

3. ENGINERED WOOD PRODUCT TYPES Strands based Oriented Strand Board (OSB) Parallel strand lumber (PSL) Parallam Veneer based Plywood Laminated veneer lumber (LVL) Lumber based Glued laminated timbers (GLULAM) Trusses Edge glued products Combinations I-Joists Structurally Insulated Panels Fiber based Wood plastic composites

4. WOOD ELEMENTS LOGS LUMBER VENEER STRANDS FLAKES PARTICALS FIBERS

5. EWP’S addresses some of woods problems Natural variability of wood – strength unpredictable, unreliable Hygrosopicity and resulting dimensional instability Biodegradable – vulnerable to decay Combustible

6. Benifts of E.W.PRODUCTS Efficient use of wood through “engineering” e.g., placing stronger and more uniform components in areas of higher stress Stable, uniform & consistent More Reliable Flexible with respect to shape Composite products - Take advantage of best properties of different materials Higher strength rating Large dimension and length possible Smaller trees are utlized Waste products are utized

7. Strong and Consistent Optimize strength through Engineered design Put strongest components where stresses are highest Configure for efficient properties Randomization of defects to reduce variability or increase reliability

8. Flexible with respect to shape and size, aesthetics

9. Laminated Veneer Lumber Elements: Sheets of wooden veneer (1/8-1/10” thick, 2’ wide, 8’ long) Product Width 1½ - 3½ inches Dimensions: Depth up to 24 inches Length up to 80 feet Applications: Beams, headers, I -beam flange

10. LVL MANUFACTURING OVERVIEW 1 2 3 4 5 6

11. LAMINATED VENEER LUMBER Softwood veneers produced as in plywood production Veneers graded prior to assembly Higher quality veneers are placed on the outsides Veneers glued with grain running parallel to each other  LVL used on flat ( I -beam flanges) or on edge (beams, headers) 11 Edge Flat

12. LVL ENDLESS DIMENSIONS Width 1 ½ in., 1 ¾ in., and 3 ½ in. Depth up to 24 in. Length up to 24m

13. Laminated Veneer Lumber Variability is reduced in one plane. Solid wood Variability is at its greatest level. Reduction of natural variability Defects in veneer can be removed or dispersed Variability is reduced Yield of veneer from logs is higher than yield of solid lumber

14. Laminated Veneer Lumber LVL beam LVL in I -beam

15. LVL - headers

16. Elements: “ Lamstock ”, high quality dimension lumber (1½” thick, up to 10” wide, up to 20’ long) Product Width 3½-14 inches Dimensions: Depth up to 8 feet Length up to 140 feet Applications: Beams, columns, arches, trusses 16 Glue Laminated Timber ( Glulam )

17. GLULAM LAMINATION Top and bottom laminations might be different species Finger joints along laminations Total dimensions = 5.25” x 17.5” (This is not a commercial sample)

18. C. Lumber-based products 1. Finger-joined lumber

19. GLUE LAMINATION LUMBER (GLULAM) Individual lamstock elements are stress-rated prior to beam fabrication Stiffer elements are placed in more critical locations in member Very large dimensions possible 19

20. GLUE LAMINATION LUMBER (GLULAM) Curved members can be created Tighter curves require thinner laminations Architectural as well as structural

21. Glulam - Columns, Beams and Rafters

22. Glulam - Curved Roof Beams

23. 2. Parallel strand lumber (PSL) Made from long narrow strands (from strander not veneer) E.g., Aspen Used for window joinery, headers…

24. Parallel strand products 3. Parallam ™ Strips of waste veneer (1/2” X 1-2’) Laid up in large molds Phenol Formaldehyde Resin – Microwave cure Mainly Douglas-fir and Southern pine Extremely strong and reliable

25. Veneer products Plywood Flat panel built up of plies of veneer through bonding C Cross-laminated for uniform transverse strength and high dimensional stability structural panels use waterproof phenol formaldehyde r resin glue certified for exterior use Face Cross-bands Core Back

26. The properties of plywood depend on the quality of the veneer plies, the order of layers, the adhesive used, and the degree to which bonding conditions are controlled during production . Plywood panels have significant bending strength both along the panel and across the panel, and the differences in strength and stiffness along the panel length versus across the panel are much smaller than those differences in solid wood uses: Construction sheathing Wall, roof sheathing Furniture Cabnite boxes and panels Box beams

27. Strand Based EWP 1. Oriented Strand Board (OSB) OSB is manufactured in a cross-oriented pattern to create a strong, stiff structural panel. OSB is composed of thin rectanglar shaped wood strands arranged in laryers at right angle to one another, which are laid into mats that form a panel OSB is bonded with fully waterproof adhesives most panels are also treated with sealent on the panel edge to guard against moisture penetration OSB has high shear strength along the edge Not recommended for exposed exterior application unless specialy treated

28. OSB - uses I-Joists Sheathing Rim board Structural insulated panels

29. 2. I-JOISTS Light Strong Long Spans Easy to put wiring, plumbing etc. through the web

30. PREFABRICATED WOOD I JOISTS Prefabricated wood I-joists are made by gluing solid sawn lumber or laminated veneer lumber (LVL) flanges and oriented strand board (OSB) panel web to produce a dimensionally stable light-weight member with known engineering properties. The uniform stiffness, strength, and light weight of these prefabricated structural products makes them well suited for longer span joist and rafter applications for both residential and commercial construction. The "I" shape of these products gives a high strength to weight ratio.

31. Efficient use of wood, Stable I-Beam is very efficient use of materials Neutral axis – Shear only Compression Tension

32. sizes The depths of prefabricated wood I-joists range from 241mm (9-1/2") to 508mm (20") Flange depths are commonly 38mm (1-1/2") and common flange widths vary from 45mm (1-3/4") to 89mm (3-1/2"). Web thickness varies from 9.5mm (3/8") to 12.7mm (1/2"). Table 1 I-Joist - Standard Depths Size mm in. 241 9-1/2 292 11-1/2 302 11-7/8 318 12-1/2 356 14 406 16 457 18 508 20

33. Trusses Structural frame relying on a triangular arrangement of webs and chords to transfer loads to reaction points. •Made from timbers or from manufactured wood products (i.e. glulam , PSL) •Members connected using bolts & plates, split rings, and special brackets & hangars

34. Trusses - Features •unlimited shape & size •economy •ease of fabrication •fast delivery •simplified erection procedures •all trusses are custom designed •flexibility in layout & longspans shapes and size restricted only by manufacturing capabilities, shipping limitations & handling considerations

35. WOOD-PLASTC COMPOSITES Any composite that contains wood & thermoset or thermoplastic Thermoset : Epoxy , Phenolics Thermoplastics: PE, PP, PVC, PS The WPCs are produced by mixing wood flour or fiber & plastics to produce a material that can be processed like a conventional plastic & has the best features of wood & plastic” Wood flour : Particulate, l/d 2:1 to 4:1 Wood fiber : Reinforcing, l/d greater than 24:1 Commonly used species : Pine, Maple Oak Typical particle size : 10 to 80 mesh

36. MANUFACTURING PROCESS Two stage Process: Compounded pellets & shaping Commonly Used processing Techniques Sheets & profile extrusion Thermoforming Compression Molding Injection Molding New Trend In-Line Compounding & Processing

37. Extrusion of WPCs

38. ADHESIVES Phenol-Formaldehyde Phenol-formaldehyde (PF) resins are typically used in the manufacture of plywood . GLULAM, oriented strandboard where exposure to weather during construction is a concern Urea-Formaldehyde Urea-formaldehyde (UF) resins are typically used in the manufacture of products used in interior applications, primarily particleboard and medium-density fiberboard (MDF),

39. ISOCYANATE The isocyanate wood adhesive is a polymeric methylene diisocyanate ( pMDI ). It is used as an alternative to PF resin, primarily in composite products fabricated from strands. pMDI resins are typically more costly than PF resins but have more rapid cure rates and will tolerate higher moisture contents Bio-Based Adhesives Bio-based adhesives, primarily protein glues, were widely used prior to the early 1970s in construction plywood. In the mid-1970s, they were supplanted by PF adhesives, on the basis of the superior bond durability provided by phenolics . The move toward “green” products has led to a renewed interest in bio-based adhesives.