7 Wood Construction Flashcards
Disadvantages to wood as construction material
Never dimensionally true
Weather will change its dimension from uneven shrink or swell
Defects, knots, holes, insects, decay, damage, splits or warping.
Wood is stronger in what direction
Parallel to the grain than against it.
Allowable tensile strength of wood
700 psi
Allowable Compressive strength of wood parallel to grain
325-1700 psi
Most structural limber has a moisture content of
19 percent or less
Different types of wood products
Solid lumber Laminated wood members. Structural composite lumber Panels Manufactured components
Glulam
Short for glue laminated structural lumber
Solid lumber includes
boards, dimensional lumber, and timbers.
Lumber boards have a nominal thickness of
2” or less
Dimensional lumber has a nominal thickness of
2-4 inches or more
Timbers have a nominal thickness of
5 inches or more
Laminated beams can have individual lamination layers of what size
3/4 to 2”. Because dimensions can be made not available in solid pieces from logs
Laminated members can be produced in depths of
3-75 inches
Three types of joints for laminated members
Scarf
Butt
Finger
But Joint is easy to produce but cannot be used when
Tensile forces are to b transmitted along the length of beam
Scar and finger joints can be used to transmit what type of force
Tensile
Veneer
Surface of attractive material laid over base of common material
Structural composite lumber SCL is composed of what types
Laminated veneer lumber LVL
parallel strand lumber. PSL
Laminated strand lumber LSL
Levels are used in applications for I joists and beams of what’s size
1.75 to 3.5 inches thick
Parallel strand lumber is the strongest of the three types of SCL and can be used for
Heavily loaded columns and long spans.
Laminated strand lumber LSL is used for
Short span beams and columns
Wood panels include
Plywood
Nonveneered panels
Sandwich or composite panels
Plywood panels have the grain oriented in the direction of the longest section with grain oriented how for the internal layers
At right angles to each other
Plywood in produced in standard sheets measuring
4x8 feet
Composite panels or sandwich panels
Produces with parallel external face veneers bonded to a core of reconstituted fibers. Example is structural insulated panel
Particle board can be in sizes up to
8x40 ft
Wafer board is similar to particle board but uses larger pieces of wood, largely been replaced by
Osb
Span rating indicates intended structural application a rating of 32/16 indicates
Use for sheeting over rafters 32 inch apart and subflooring over joists 16 inches apart.
Lumber
Lengths of wood cut and prepared for use in construction
Gusset plates
Metal or wooden plates used to connect and strengthen the intersections of metal or wood truss components
Light frame trusses
Made of 2 inch nominal members that are all in the same plane. Popular for roof framing, belt together by metal toothed gussets or plywood nailed.
Heavy timber trusses
Made of members 8 or 10 inches. Common before the use of steel