Steel Buildings in Europe

Part 1: Architect’s Guide 1 - 16 Figure 3.5 Typical roof and wall bracing in portal framed structures In most cases, the rafter (and possibly the column) will need local restraints, as shown on Figure 3.6. In some countries, special provision must be made when using this form of restraint, to ensure that the purlins align with the roof bracing system. The location of these restraints will be specified by the structural engineer. Figure 3.6 Stabilizing the bottom flange of a roof beam Rigid framed trusses When flat trusses are used, both top and bottom chords can easily be connected to the supporting columns, thus creating a rigid frame. For larger spans, roof trusses provide an effective and economic alternative. Typical flat truss shapes are shown in Figure 3.7, and a truss roof is illustrated in Figure 3.8.