Lexicon
Roof trusses

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In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in forces in the members which are either tensile or compressive forces. Moments (torsional forces) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes.

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Drawings by Frank Gaylard from: Fisher, Roger C. 1992. Visual Lexicon of the South African Dwelling. Cape Town: Unibook. p, 34-35.