WOOD - Materials for Civil and Construction Engineers - page 403

tested to have specific mechanical responses to loads. Structural engi-
neered wood products include the following:
■ structural panels including plywood, oriented strand board, and
composite panels,
■ glued laminated timber (glulam),
■ structural composite lumber, and
■ composite structural members.
5. Specialty items are milled and fabricated products to reduce on-site
construction time, includes lattice, handrails, spindles, radius edge
decking, turned posts, etc.
Sawn wood production includes the following steps:
■ Sawing into desired shape
■ Seasoning
■ Surfacing
■ Grading
■ Preservative treatment (optional)
Surfacing (planing) of the wood surface, to produce a smooth face, can be
done before or after drying. Post drying surfacing is superior, because it re-
moves small defects developed during the drying process. When surfacing
is done before seasoning, the dimensions are slightly increased to compen-
sate for shrinkage during seasoning.

■ 10.4.1 Cutting Techniques

The harvested wood is cut into lumber and timber at saw mills using cir-
cular saws, band saws, or frame saws. The most common patterns for saw-
ing a log are plain (slash), quarter , and combination sawing , as shown on
Figure 10.6. (Levin, 1972).
The quality of the boards is related to the angle the growth rings make
with the face of the board (i.e., the angle between the growth ring and the
saw blade). There are three categories, as illustrated in Figure 10.7:

1. Flat-sawn, 45° or less
2. Rift-sawn, 45° to 80°
3. Vertical- or edge-sawn, 80° to 90°

(a) (b) (c)

FIGURE 10.6 Common log sawing patterns: (a) plain saw-
ing, (b) quarter sawing, and (c) combination sawing.