Roof trusses become essential when sloping roofs have to be provided. At places of heavy rainfall or heavy snowfall sloping roofs are necessary which have to be supported by roof trusses. Workshops warehouses, industrial buildings etc. also need sloping roofs and hence roof trusses. For many single story buildings sloping roofs on trusses are common. When a roof is to be provided for a building which does not have interior supports and the exterior walls are more than 12 m apart, a roof truss will be a convenient arrangement to support the roof.
Components of a Steel Roof Truss:
A roof truss consists essentially of the following components:
(i) Upper chord members.
(ii) Bottom chord members.
(iii) Web members.
The upper most line of members which extend from one support to the other through the apex is called the upper chord, where as the bottom chord consists of the lowermost line of members extending from one support to the other.
In trusses simply supported at the ends, the members in the top chord are subjected to compression and the members of the bottom chord are subjected to tension. But in cantilever trusses, the top chord members will be in tension and the bottom chord members will be in compression. Usually in simply supported trusses, for the normal loadings, the top and bottom chord members near the support carry greater forces.