<P> The simplest form of a truss is one single triangle . This type of truss is seen in a framed roof consisting of rafters and a ceiling joist, and in other mechanical structures such as bicycles and aircraft . Because of the stability of this shape and the methods of analysis used to calculate the forces within it, a truss composed entirely of triangles is known as a simple truss . However, a simple truss is often defined more restrictively by demanding that it can be constructed through successive addition of pairs of members, each connected to two existing joints and to each other to form a new joint, and this definition does not require a simple truss to comprise only triangles . The traditional diamond - shape bicycle frame, which utilizes two conjoined triangles, is an example of a simple truss . </P> <P> A planar truss lies in a single plane . Planar trusses are typically used in parallel to form roofs and bridges . </P> <P> The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form . A solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss . For a given span, a deeper truss will require less material in the chords and greater material in the verticals and diagonals . An optimum depth of the truss will maximize the efficiency . </P> <P> A space frame truss is a three - dimensional framework of members pinned at their ends . A tetrahedron shape is the simplest space truss, consisting of six members that meet at four joints . Large planar structures may be composed from tetrahedrons with common edges, and they are also employed in the base structures of large free - standing power line pylons . </P>

Where's the load carried when a roof truss system is in place