TRUSS

A truss is essentially a triangulated system of (usually) straight interconnected structural elements; it is sometimes referred to as an open web girder. The individual elements are connected at nodes; the connections are often assumed to be nominally pinned. The external forces applied to the system and the reactions at the supports are generally applied at the nodes. When all the members and applied forces are in a same plane, the system is a plane or 2D truss. The principal force in each element is axial tension or compression. When the connections at the nodes are stiff, secondary bending is introduced.

Use of trusses in single-storey buildings 

In a typical single-storey industrial building, trusses are very widely used to serve two main functions: 

• To carry the roof load
• Gravity loads (self-weight, roofing and equipment, either on the roof or hung to the structure, snow loads) 
• Actions due to the wind (including uplift due to negative pressure). 
• To provide horizontal stability: 
• Wind girders at roof level, or at intermediate levels if required 
• Vertical bracing in the side walls and/or in the gables.

Types of connections 

For all the types of member sections, it is possible to design either bolted connections or welded connections. Generally, bolted connections are preferred on site. Where bolted connections are used with bolts loaded perpendicular to their shank, it is necessary to evaluate the consequences of slack in connections. In order to reduce these consequences (typically, the increase of the deflections), solutions are available such as use of pre-stressed bolts, or limiting the hole size.