Steel Buildings in Europe

Part 8: Building Envelope 8 - 26 Single-span lengths - butted system Single-span butted systems have a lower capacity than the other systems, but are simpler to fix either over the rafters or between rafter webs (Figure 4.4). This layout may be used for small buildings with close frame centres, such as agricultural applications. 1 Single-span purlin 2 Rafter Figure 4.4 Single-span lengths - butted system Single-span lengths - overlapping system An overlapping system provides greater continuity and can be used for heavy loads and long spans (Figure 4.5). It is best suited to buildings with a large number of bays. 1 Purlin 2 Rafter Figure 4.5 Single-span lengths - overlapping system Double-span lengths – non sleeved system In this system, the double-span lengths are staggered (Figure 4.6). Sleeves are provided at the penultimate supports to ensure semi continuity. The capacity will generally be less than for the equivalent double span sleeved system, but double-span purlins use fewer components and lead to faster erection. This system is limited to bay sizes less than 8 m, for reasons of transport and erection of the purlins.