Carpentry 2: Residential Truss System Part A

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Carpentry 2: Residential Truss System Part A
2014-05-28 13:23:13
Carpentry 2: Residential Truss System Part A
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  1. What is a trussed rafter?
    A pre-assembled unit built to form the shape of desired roof style
  2. What distances can modern trusses span without the installation of intermediate load-bearing partition walls?
    In excess of 18m (60ft)
  3. How do increased spans affect the interior design of a building?
    Large rooms can be created without load bearing walls or beams and columns
  4. What is the maximum allowable moisture content for lumber used in the manufacture of trusses at the time of construction?
  5. In the last 50 years, what advance in design/construction of trusses has had the greatest impact on the development of truss?
    Metal connector plates
  6. What are the 2 most common sizes of material used in the construction of wood trusses?
    • 2x4 (38mm x 89mm)
    • 2x6 (38mm x 140mm)
  7. How are truss connector plates attached to the truss member?
    Pressed or rolled into place by means of large hydraulic presses that exert well in excess of 1000 lb /sq inch. Most presses exceed 60 tons in capacity.
  8. Which truss design is prone to horizontal deflection as well as to vertical deflection?
    Scissor truss
  9. A roof with a single slope (shed roof) is built using which type of truss?
    Mono truss
  10. What are the names of the 2 styles of flat roof trusses?
    • Pratt
    • Warren
  11. When would you use a combination truss?
    When there is 2 different roof/ceiling slopes
  12. Why should connector plates not be installed with a hammer?
    They won't develop resistance for which they were made
  13. What is a girder truss?
    Composed of 2 or more trusses laminated together to form a single truss capable of transferring much greater loads than a single truss.
  14. Where can the instructions for the proper lamination of a girder truss be found?
    Included with truss documentation (shop drawings)
  15. Loads can be divided into 2 groups. What are they?
    • Live
    • Dead
  16. Which type of load is a layer of roofing plywood attached to the trusses?
  17. Which type of load is a pile of roofing plywood placed on the roof trusses prior to installation?
  18. What is a point load?
    • Concentration of loading in 1 area of building or roof.
    • An air conditioning unit would be a point load on a roof.
  19. What are the 2 basic forces that continually act on a truss?
    • Tension
    • Compression
  20. On what does the compressive strength of a member depend?
    On its unsupported length. The longer it is the less resisitance
  21. What is the purpose of the lateral bracing that is installed on the various members of a truss?
    To reduce unsupported length
  22. Against what type of forces is wood the weakest?
    Tension perpendicular to the grain
  23. Why has the 1/2" Maximum Bearing Gap Rule been established for the installation of certain types of trusses?
    Study has shown that this helps reduce truss failure due to horizontal shear
  24. How can the amount of deflection in a particular member be decreased without decreasing the unsupported length of the member?
    By increasing depth of the member
  25. Which truss will deflect the most given the same span and loading: a higher pitched truss or a lower pitched truss?
    Lower pitch deflects more
  26. What can be done to help eliminate the movement in the walls of a building when the truss being installed is prone to horizontal deflection?
    Special truss hangers that allow horizontal deflection independent of the wall can be installed. (allow the truss to slide in and out)