Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 46 1 2 3 4 1 Vertical bracing on gable 2 Vertical bracing on elevation 3 Roof bracing 4 Portalised bracing in elevation Figure 9.8 Portalising an opening on one side with conventional bracing on the other side of the structure 9.2.7 Bracing to restrain columns If side rails and column stays provide lateral or torsional restraint to the column, it is important to identify the route of the restraint force to the vertical bracing system. If there is more than one opening in the side of the building, additional intermediate bracing may be required. This bracing should be provided as close to the plane of the side rail as possible, preferably on the inside face of the outer flange (Figure 9.9). 5 2 4 3 1 1 Eaves beam 2 Doorways 3 Side rail restraining column stay 4 Additional bracing required in this bay on the inner face of the outer flange 5 Position of plan bracing Figure 9.9 Typical bracing pattern in side of building with openings It is not normally necessary for the side rail that provides restraint at column stay positions to be aligned with a node of the vertical bracing system. It can be assumed that diaphragm action in the vertical sheeting and the transverse stiffness of the column can transmit the load into the vertical bracing system. Where a member is used to restrain the position of a plastic hinge in the column, it is essential that it is tied properly into the bracing system. This can result in the configuration shown in Figure 9.10. Where there is more than one