Steel Buildings in Europe

Part 1: Architect’s Guide 1 - 12 3 FORM OF PRIMARY STEEL STRUCTURE Single storey steel buildings are generally built with an external cladding envelope, supported in many cases on relatively short span secondary steel members, which are in turn supported on the primary steel structure. This Section describes the structural possibilities that may be considered and comments on the type of structural sections that can be used. 3.1 Structure types There are four basic structural configurations that provide a clear interior space for a single storey building:  Rigid framed structures (portal frames and rigid-frame trusses)  Pinned frame beam-and-column structures  Cable-supported roofs  Arched roofs For the first three configurations, the designer has the option of providing either a flat roof or a pitched roof. Typical spans and span/depth ratios for the primary roof members in pinned and rigid framed buildings are given in Table 3.1. Table 3.1 Typical spans and structural depths for single storey structures Structure type Roof beam depth Typical span range Pinned frames Simple beam span/30 to span/40 Up to approximately 20 m Fabricated Beam span/20 to span/25 Up to approximately 30 m Perforated web beam span/20 to span/60 Up to approximately 45 m Truss roof (pitched) span/5 to span/10 Up to approximately 20 m Truss roof (flat) span/15 to span/20 Up to approximately 100 m Rigid frames Portal frame span/60 15 m – 45 m Truss roof (flat) span/15 to span/20 Up to approximately 100 m 3.1.1 Rigid-framed structures Rigid frames are achieved by providing a rigid (moment resisting) connection between the ends of the roof beams (or trusses) and the columns. The stiff frame that is created is much more efficient in carrying the imposed loads on the roof than a simply supported roof member (with nominally pinned connections at its ends) and the frame also provides resistance against wind forces on the sides of the building. Because the frames are self-supporting in the plane of the frame, the bracing in the roof can be reduced, compared to a structure with simply supported roof beams. Rigid framed structures broadly fall into two categories, portal framed structures and truss framed structures.