EJMS Technology Education
Truss Types and Parts
Last
updated on September 13, 2002
Types of Trusses
There are many variations of truss designs in the world. In the picture
below, you can see some of the major types that are used to build bridges.
Notice that several of them look
a lot alike. This is due to many people working over hundreds of years to
increase the strength and efficiency of truss designs. Which ones do you
think are the older designs? Which ones have been developed from earlier
designs?
Notice that there are many triangular sections in each type of truss. The
triangle is the geometric shape that has the least amount of flexibility. By
using many combinations of triangles in a truss, the unit can be designed to
carry a great deal of weight or pressure. And, the triangular sections allow
smaller pieces of lumber or metal to be used to carry the load. This gives us a
very strong truss unit that is fairly lightweight to handle and less expensive
than solid wood beams or large metal beams.
Parts of Trusses
Upper Chord - defines the top or a roof or bridge truss and helps carry the
weight of roofing materials or snow.
Lower Chord - determines the distance the truss can span (or reach across),
and helps transfer the load carried by the truss to each end of the bridge or
building.
Web Members - add bracing to the upper and lower chords. They help keep
the truss sturdy, help transfer the load to each end of the truss, and keep
the truss from twisting. They give the truss much of its strength.
Gussets - thin pieces of plywood or metal used to join the parts of a
truss together.
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