Open Truss Roof Structure

The benefit of a truss over older structural designs like coupled rafters is that it provides longitudinal support.

Open truss roof structure.

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. A roof truss is a structural unit designed to frame a roof and to support the roof material interior ceiling insulation and forces caused by snow rain and wind. A roof truss is supported by the exterior walls and span the width of the building. 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.

Rafters have a tendency to flatten under gravity thrusting outwards on the walls. In essence a roof built on trusses is much more structurally sound. Trusses are gradually replacing the conventional rafters to the point that nowadays more than 80 percent of new residential construction uses trusses to support the roof. In most truss members only flexural buckling of the compressed members in the plane of the truss structure and out of the plane of the truss structure need be evaluated.

The buckling resistance is obtained from bs en 1993 1 1 2 by applying a reduction to the resistance of the cross section. Components of roof truss. A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof trusses usually occur at regular intervals linked by longitudinal timbers such as purlins the space between each truss is known as a bay.