Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 53 10 GABLES 10.1 Types of gable frame Gable frames are typically of two forms:  An identical portal frame to the remainder of the structure. The gable columns do not support the rafter. This form of gable is used for simplicity, or because there is the possibility of extending the structure in the future.  A gable frame comprising gable posts and simply supported rafters. The gable posts support the rafters. Gable frames of this form require bracing in the plane of the gable, as shown in Figure 10.1. The advantage of this form of gable is that the rafters and external columns are smaller than those in a portal frame. Figure 10.1 Gable frame from columns, beams and bracing 10.2 Gable columns Gable columns are designed as vertical beams, spanning between the base and the rafter. At rafter level, the horizontal load from the gable column is transferred into the roof bracing, to the eaves, and then to the ground via the bracing in the elevations. The gable column will be designed for pressure and suction. The maximum suction may be when the gable is on the downwind elevation, as shown in Figure 10.2(a), or more likely when the gable is parallel to the wind direction, as shown in Figure 10.2(b).