HC-Lecture06-Wood

HC-Lecture06-Wood - Heavy Construction Heavy Lecture #06...

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Heavy Construction Heavy Construction Lecture #06 Lecture #06 Wood L Prieto-Portar 2008
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A typical “stick construction” house, using wood studs and particle-board sheathing.
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The floor system of a residence serves for the roof of a basement.
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Qualities of Wood - Strong and stiff - Light - Easily worked or shaped - Fastens quickly and economically - Recyclable - Biodegradable - Renewable resource Undesirable Characteristics of Wood - Not perfectly straight nor cut precisely - Size and shape is affected by moisture - Contains growth defects - Can spilt and warp - Burns easily - Decays - Susceptible to insect damage
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Parts of a Tree for use as Timber. Bark Cambium Sapwood Heartwood Pith (protective layer; dead outside, and alive inside) (very thin; creates new cells) (stores nutrients and transmits the sap; living portion of the trunk) (dead; provides structural stability) (early years growth; small and weak)
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The Tree’s Cells. The cells are primarily hollow and cylindrical (called “tracheids”). Their axis runs parallel to the tree’s height (grain direction), made from tough cellulose bound by lignin. It affects the properties of wood. To understand their structural behavior, imagine them as a group of straws bound together. That makes the wood strong parallel to the grain, and much weaker perpendicular to the grain.
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The Tree’s Growth Cycle. The springwood (or early-wood) has a faster growth, and the cells are larger and less dense. The summerwood (or late-wood) has a slower growth with smaller cells and denser.
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Oak Poplar Pine - Softwoods (coniferous) are simple, coarse grain. Common trees are pine, spruce, fir and cedar. These are the most common lumber in building because they grows faster, and hence much more economical. - Hardwoods , are broad leafed trees, with a more complex cell structure, leading to beautiful grain patterns. Used primarily for furniture, doors, trims and accents. Common trees are oak, poplar, walnut and maple.
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Construction Uses for Wood. 1) Structural framing. 2) Sub-floors and roof sheathing. 3) Siding: structural and exposed. 4) Finish carpentry, cabinetry and trim. 1 2 3 4
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Lumber Production – Sawing. - Plain sawing: produces maximum yield, but causes varying grain patterns and much distortion. It is acceptable because it usually is not seen, since it is used primarily for structural work. The maximum yield keeps the price down. Commonly termed framing lumber.
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- Quarter sawing: cut perpendicular to the annual rings. It has less yield than plain sawing, but the grains have a consistent pattern. The cut also improves the lumber’s wearing quality, and has less distortion.
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- Typical Sawing Method: optical scanners and computer software now selects the best way to cut up a log, to reduce waste and costs.
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Drying Lumber. Green wood may be as much as 300%
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This note was uploaded on 09/15/2011 for the course CCE 4001 taught by Professor Staff during the Fall '08 term at FIU.

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HC-Lecture06-Wood - Heavy Construction Heavy Lecture #06...

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