Light Frame Trusses
Light frame trusses are
used in a variety of residential and commercial applications. Spans up to 20m
(60') are common although longer spans are also feasible. The shape and size of
these trusses may be restricted by shipping and handling considerations.
Parallel chord trusses
are widely used for floor systems and flat roof systems and are often more
economical than open web steel joist systems.
Some types of parallel
chord (flat) trusses utilize steel tension members. These composite wood/steel
trusses, like most other wood trusses, are generally custom designed.
Parallel chord trusses
may be supported either at the top or the bottom chord and may be ordered with a
built in camber to offset deflection and to provide positive drainage when used
as a flat roof system.
The long span
capabilities of flat trusses permit large bay sizes. They reduce the need for
intermediate support required for conventional floor joists using dimension
lumber, beams or prefabricated wood I-joists.
Electrical, plumbing,
heating and air conditioning services may be placed between the truss chords.
These particular requirements must be specified for inclusion in the overall
design of the truss system.
General intormation on
span, slope and loading conditions is published by the truss fabricators. Due to
the wide range in requirements of each construction project, the general
information should be used as a guideline for reference purposes only. Specific
loadings and other structural requirements must be clearly identified for proper
design of any truss system. In designing the appropriate trusses, the truss
manufacturer will incorporate these specifications with the architectural
requirements.
Heavy Timber Trusses
Heavy timber trusses are
made from timbers, or from manufactured wood products, such as glulam or
parallel strand Iumber (PSL), havlng the dimensions of timbers. Connections for
members are made by using bolts and plates, split rings and special brackets and
hangers. Heavy timber trusses provide long spans for applications where the
space required for the depth of the trusses can be accommodated into a building
plan.
Heavy timber trusses are
often used to provide special architectural features such as open vaulted
ceilings. They are usually custom designed by structural engineers to be used
for roof and floor systems in residential and commercial buildings. They are
usually field assembled rather than factory manufactured as in the case of light
frame trusses.
Some types of heavy
timber trusses, such as the bowstring trusses, use steel tension members for
additional strength.
Previous
Page