CE403 Construction Methodology

1. CE403 Construction Methodology Wood Construction

2. Wood Construction • Workability • Joinability • Easy Handling • Relatively Low Cost • Natural Beauty Advantages Disadvantages • Combustability • Moisture Expansion • Termites & Fungi • Defects

3. Going Metric • Hard Conversion • Plywood: from 4 x 8 to 1200 x 2400 mm • Spacing: from 16” o.c & 24” o.c. to 400 mm or 600 mm • 2 x 4 will be called “50 x 100 mm” • Otherwise, soft conversion

4. Wood Anatomy Basics • Grain: cell structure configuration • Summer wood & Spring Wood • Anisotropic: Grain direction drives properties • Parallel: high strength & low strain • Perpendicular: high strain

6. Wood Anatomy Basics • Grain: cell structure configuration • Summer wood & Spring Wood • Anisotropic: Grain direction drives properties • Parallel: high strength & low strain • Perpendicular: high strain

7. Wood Properties • Species dependent • Hard woods: deciduous • Soft woods: evergreen (typically); Conifers (always –needles) – 75% of U.S. Commercial Lumber • Moisture content dependent • Strength; shrinkage • Wide ranging density • 25-50 lb/cf.

8. Moisture Content • (Wmoist – Wdry)/Wdry • Seasoned: < 15% M.C. • Fiber Saturation Point (FSP): • Only bound water, no free water • M.C.: 20-30% depends on species • M.C. < F.S.P.: shrinkage; increased strength

9. Doug. Fir/So. Pine Properties • Density 30lb./cf • E 1,500 ksi • Fy – tensile 8,000 psi parallel • Fy – compressive 3,500 psi parallel 350 psi perpend. • Working stress modifiers: load duration, defects

10. Wood Processing: 4 Steps • Saw Plain sawn vs. quarter sawn • Season < 15% moisture content • Surface • Grade

12. Wood Processing: 4 Steps • Saw Plain sawn vs. quarter sawn • Season < 15% moisture content • Surface • Grade

13. Grade Defects • Natural: • Shake and Knots

14. Grade Defects - Knots

15. Grade Defects – due to seasoning

16. Grade Defects – due to seasoning

17. Grade Defects – due to surfacing • Wane

18. Unit of Measure: Volume • Board Foot • In rough, green condition • 12” x 12” x 1” (144 cu. In) • MBF or MBM = 1000 board feet • Nominal versus Actual dimensions • Nominal: the intended or approximate size but this may (and often does) vary from the actual dimension.

20. Plywood • Glued together plies • Plies shaved from rotating log • Each ply is approx. 1/8” thick • Odd number of plies – 3, 5, 7, & 9 • Plies seasoned to 5% moisture content. • Grain direction alternates

21. Plywood Veneers

22. Plywood • Glued together plies • Plies shaved from rotating log • Each ply is approx. 1/8” thick • Odd number of plies – 3, 5, 7, & 9 • Plies seasoned to 5% moisture content. • Grain direction alternates

23. Plywood • Grain is parallel to long dimension on outer face (strong direction) • Exterior vs. interior grade: type of adhesive • Interior: water resistant • Exterior: waterproof

24. Plywood Grades

25. Plywood Grades

26. Residential Framing • Platform vs. Balloon Framing • Ease of construction vs. structural strain • Bridging between joists • Helps distribute point loads • 2 types: cross bridging and solid blocking • Plywood box beams

27. Platform Frame

28. Balloon Frame

29. Residential Framing • Platform vs. Balloon Framing • Ease of construction vs. structural strain • Bridging between joists • Helps distribute point loads • 2 types: cross bridging and solid blocking • Plywood box beams

30. Plywood Box Beams

31. Residential Framing

32. Rafters & Roof Trusses • Advantages of Roof Trusses: • Interior walls can be nonbearing; • Economy; • Controlled quality; and • Less Skilled Labor required

33. Stair Framing

35. Glu-Lam Members • Built-up glued laminations of dimension lumber • Very large sections & spans possible • Cheaper material than solid beam • Defects can be eliminated • Unique shapes possible: curved frames, arches

36. Connections: Nails • Size: “penny” designation (d) • Based on original cost of 100 nails • Sold by 100 lb. keg • Many Types: • Common • Casing • Finishing • Specialty: concrete, roofing, drywall, siding…

37. Nails

38. Nail Connection Configuration & Strength • Strongest • Nail perpendicular to grain • Nail subjected to shear • E.g. face nailing • Weakest • Nail parallel to grain • Nail subjected to withdrawal forces • E.g. end nailing

39. Nailed Connection Configuration • Relative to board face, edge, or end • Face Nailing – face-to-edge, face-to-face • End Nailing – face-to-end • Toe Nailing – angled thru edge-to-edge, or angled thru face-to-face • Specialty configurations • Blind nailing – flooring to subflooring

40. Nail Connection Configuration

41. Screw & Bolt Connections • Common to both: • Head • External threads • Screws: threads in contact with wood fibers; usually pointed (vs. blunt) • Bolts: threads in contact with nut • Washers between bolt head/wood and nut/wood

42. Bolts and Screws

43. Split Ring Connector • Ring-shaped metal insert placed in pre-cut circular grooves in two wood members and held together by a bolt/nut • Distributes shear load over larger area • Good for large shear loads • Very large truss joints

44. Split Ring Connector