Steel Buildings in Europe

Part 2: Concept Design 2 - 3 Simple beam Portal frame Truss Portal truss Figure 1.1 Structural concepts The basic design concepts for each structural type are described below: Simple roof beam, supported on columns. The span will generally be modest, up to approximately 20 m. The roof beam may be pre-cambered. Bracing will be required in the roof and all elevations, to provide in-plane and longitudinal stability. Portal frame A portal frame is a rigid frame with moment resisting connections to provide stability in-plane. A portal frame may be single bay or multi bay as shown in Figure 1.2. The members are generally plain rolled sections, with the resistance of the rafter enhanced locally with a haunch. In many cases, the frame will have pinned bases. Stability in the longitudinal direction is provided by a combination of bracing in the roof, across one or both end bays, and vertical bracing in the elevations. If vertical bracing cannot be provided in the elevations (due to industrial doors, for example) stability is often provided by a rigid frame within the elevation. Trusses Truss buildings generally have roof bracing and vertical bracing in each elevation to provide stability in both orthogonal directions, as in Figure 1.4. The trusses may take a variety of forms, with shallow or steep external roof slopes.