Material Properties

1. Material Properties Wood Decays Burns Low strength Easy to shape

2. Concepts: Wood Standard sizes and lengths Connections Grading Seasoning

3. Assemblies: Wood Field fabrication and assembly Prefabrication Trusses Glue lamination

4. Terminology and Classification The terms wood, lumber, and timber are often used interchangeably, but each term has a distinct meaning. Wood is the hard fibrous substance lying beneath the bark of trees.

5. Terminology and Classification The terms wood, lumber, and timber are often used interchangeably, but each term has a distinct meaning. Wood is the hard fibrous substance lying beneath the bark of trees. Lumber is wood that has been sawn into construction members.

6. Terminology and Classification The terms wood, lumber, and timber are often used interchangeably, but each term has a distinct meaning. Wood is the hard fibrous substance lying beneath the bark of trees. Lumber is wood that has been sawn into construction members. Timber is lumber that is five inches or larger in its least dimension.

7. Terminology and Classification Wood is classified as softwood or hardwood depending on the type of tree it originates from. SOFTWOODS, such as pine, fir, and spruce, come from needle-leaved conifers, which are evergreen HARDWOODS, such as maple, oak, and sycamore, come from broad-leaved deciduous trees, which shed their leaves annually.

8. Terminology and Classification Wood is classified as softwood or hardwood depending on the type of tree it originates from. SOFTWOODS, such as pine, fir, and spruce, come from needle-leaved conifers, which are evergreen HARDWOODS, such as maple, oak, and sycamore, come from broad-leaved deciduous trees, which shed their leaves annually. Fun fact: one of the softest woods known is balsa wood, which is actually a hardwood. The important difference between Softwoods and Hardwoods is botanical, which refers to the cellular structure of the two groups. Most hardwoods are in fact harder than softwoods; however balsa wood is one of nature’s contradictions.

9. Characteristics of Wood Wood consists of approximately 70% cellulose and 18% to 28% lignin, which is the adhesive imparting strength to the wood. The remainder is made up of minerals and extractives, which give wood its color, odor, and resistance to decay. Wood is generally stronger in compression than tension. Unlike other materials, the strength of wood is not the same in every direction: for tension and compression.

10. Wood is stronger when the load is applied parallel to the grain than perpendicular to the grain. In fact, the strength of wood in tension perpendicular to the grain is so low that this type of loading can easily cause the wood to split. T = Tension C= Compression

11. Wood is stronger when the load is applied parallel to the grain than perpendicular to the grain. In fact, the strength of wood intension perpendicular to the grain is so low that this type of loading can easily cause the wood to split. T = Tension C= Compression For shear, wood is very strong perpendicular to the grain and relatively weak parallel to the grain. Therefore, horizontal shear stress (parallel to the grain) is often a design consideration, while vertical shear stress (perpendicular to the grain) is not.

12. Seasoning of Wood shrinkage stiffness strength Making wood suitable for construction involved more than simply cutting down a tree and sawing the wood to size. Wood in a tree isgreen, that is, contains a large amount of water. If green lumber is used in construction, it will shrink as it dries out.

13. Seasoning of Wood Making wood suitable for construction involved more than simply cutting down a tree and sawing the wood to size. Wood in a tree isgreen, that is, contains a large amount of water. If green lumber is used in construction, it will shrink as it dries out. To minimize shrinkage, lumber should be seasoned (dried) before installation. This can be accomplished by air drying, which takes several months and leaves 10% to 20% moisture in lumber. OR kiln drying, which takes only a few days and leaves less that 10% moisture. Framing lumber is considered seasoned if its moisture content is 19% or less.

14. Seasoning of Wood As moisture content in the cells of wood changes, particularly as it dries out, wood members can change shape if the change moisture content is not done in controlled conditions. As wood dries out the amount of shrinkage differs in various directions.

15. Seasoning of Wood As moisture content in the cells of wood changes, particularly as it dries out, wood members can change shape if the change moisture content is not done in controlled conditions. As wood dries out the amount of shrinkage differs in various directions. Shrinkage is limited to parallel to the grain of the wood.It is greatest when measured in a tangent to the growth rings. The amount of shrinkage along the radius of the wood is less than that tangentially. Depending on where in the log the member is cut from, uncontrolled drying can cause wood members to exhibit unusual shapes as shown here in this exaggerated illustration.

16. Cutting and Sawing Lumber Shrinkage, distortion, and warpage of lumber depends partially on the way lumber is cut from a tree. Wood shrinks most in the direction of the annual growth rings (tangentially); less across these rings (radially); and very little parallel to the grain (longitudinally).

17. Cutting and Sawing Lumber Lumber can be cut from a log in two different ways: tangent to the annual rings, called plain-sawed in hardwoods and flat-grained or slain-grained in softwoods. Lumber cut radially to the annual rings is called quarter-sawed in hardwoods, and edge-grained or vertical-grained in softwoods.

18. Cutting and Sawing Lumber Lumber is classified as quarter-sawed if the grain is 45 degrees to 90 degrees to the wide face and plain-sawed if the grain is 0 degrees to 45 degrees to the wide face.

19. Cutting and Sawing Lumber • Characteristics of plain-sawed lumber include: • Distinct grain pattern, • May twist, cup, or wear unevenly, • Tends to have a raised grain, • Shrinks and swells more in width, less in thickness, • Less waste in cutting, and therefore less expensive.

21. Cutting and Sawing Lumber • Characteristics of plain-sawed lumber include: • Distinct grain pattern, • May twist, cup, or wear unevenly, • Tends to have a raised grain, • Shrinks and swells more in width, less in thickness, • Less waste in cutting, and therefore less expensive. • Characteristics of Quarter-sawed lumber include: • Relatively even grain pattern, • Wears evenly with less warpage, • Shrinks and swells more in thickness, less in width, • More waste in cutting and therefore more costly.

22. What is considered an acceptable moisture content of framing lumber? • Of finish lumber?

23. Wood Defects Variety of defects that affect the strength, appearance, use, and grading of lumber. Defects may be natural or caused by manufacturing. Wood can be damaged by insects, decayed by fungus, and of course, destroyed by fire.

24. Wood Defects NATURAL DEFECTS: Knot: branch embedded in a tree and cut through manufacturing. Shake: pitted area sometimes found in cedar and cypress. Pitched Pocket: opening between growth rings and containing resin.

25. Wood Defects MANUFACTURED DEFECTS: Check: lengthwise grain separation caused by seasoning. Split: lengthwise separation of wood extending from one face to another. Wane: lack of wood on the edge or corner. Warp: shrinkage distortion of a plane surface, includes---bow, crook, cup and twist.

26. Standardized terms and dimensions

27. Standardize Dimensions – Nominal Verse Actual size

28. Plywood Veneer Cutting

29. Miscellaneous Panels

32. Lab #1: Gluelam Construction ● Thursday Aug. 28 ● Meet in Woodshop • The exercise addresses the construction of glue-laminated beams. Students will work in teams of two. Please bring all the required materials, sketchbooks, pencils, scale, etc, necessary to complete the project. It is recommended that students purchase the materials in teams of six for economy and efficiency and precut as much as possible before class. • For each team of TWO students: • 1) 16”x32”x3/4” MDF board to serve as the construction platform for your design. A full 48”x96” panel of will produce six boards. • 2) ½” Wood cylindrical dowels long enough to produce the number required for your design. Length will be approx 1 ¾” each depending on design. • Drill completely through ¾” construction platform for secure attachment. • 3) Wood glue • 4) Crisco (lard) to be shared between approx. three to four teams. Smear Crisco on the construction platform to keep your gluelam wood strips from sticking. • 5) 30 pieces of 1/16” thick x1” wide x ______long (at least 16” long) balsa or bass wood strips depending on the radius bend of your design • 6) Clamps for additional support of gluelam member beyond use of the dowels during the forming process. • Ten bags of clamps at the Wal-mart near SPSU have been special ordered. 16 assorted clamp sizes in the package for $9. Available Monday in the Hardware Dept. • 7) Safety glasses – must be worn by any student operating power equipment. • Notes: • ● Precut as many of your construction members as possible before class. • Woodshop hours: M T W F 10AM – 7PM. Thursdays 9AM – 6PM • Woodshop phone number: 678-915-5537 • ● Presoaking the wood strips in water will aid in their bending without snapping. • ● Review last years Powerpoint on line: ARCH3311 Gluelam Lab 2007.ppt on class website: http://architecture.spsu.edu/classes/3311%20-2008/

33. Wood

34. Structural Strength of Wood • Species ( Fir, Hemlock, Pine, etc) • Grade • Direction of Grain ( parallel or perpendicular) • Size and Shape • Moisture Content

37. Definition of Moisture Content Weight of water compared to the weight of dry wood • Formula for Moisture Content Weight of water as % of wt. of dry wood

38. What is considered an acceptable moisture content of framing lumber? 19%

39. Engineered Wood Products • OSB • LVL • Plywood • Particle Board • Glulam • MDF • I-Beams • Trusses

40. Particle Boardmanufactured from wood particles, such as wood chips, sawmill shavings, or even saw dust. Made with larger pieces of wood than used to make MDF

41. Oriented Strand Board (OSB)

42. Oriented Strand Board (OSB)

43. Medium Density Fiberboard (MDF)Combination of softwood fibers, wax & resin. Stronger than particle board

44. Laminate Strand Lumber (LSL)Made up of strands of lumber instead of veneers

45. Laminated Veneer Lumber (LVL) LVL is made by gluing sheets of veneer together. Unlike plywood, here all veneer layers are going in the same direction. Wide panels are manufactured to the thickness of the desired lumber. The panels are ripped into lumber of nominal width.

46. MasoniteType of hardboard invented by William H. Mason.[1] It is formed using the Mason method, using wooden chips and blasting them into long fibers with steam and then forming them into boards. The boards are then pressed and heated to form the finished boards. No glue or other material is added.

47. Plywoodmade from thin sheets of wood veneer, called plies or veneers, layered in opposite directions

48. Plywood Plywood is classified as interior or exterior depending on the type of adhesive used: moisture-resistant for interior use, and water-proof for exterior use. Plywood used in construction is primarily softwood. Plywood used for interior millwork or cabinetry is usually hardwood. Plywood is graded according to quality of the veneer: A BestD poorest.

49. Wood I-BeamsVeneer lumber is used for the flanges and plywood or OSB is used for the web to resist shear.

50. Glued Laminated Lumber (Glulam) These beams are made by gluing many boards together to form a structural member bigger than the trees from which the board were sawn. Since the load is carried by the material in the top and bottom faces and the middle only has to resist shear, high quality lumber is used in the top and bottom while medium grade lumber is used in the center. (gluelam or glulam) Joints between boards are typically scarf of finger joints.