Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 26 6.3 Out-of-plane restraint (a) (b) (c) Figure 6.2 Types of restraint to out-of-plane buckling Figure 6.2 shows the three basic types of restraint that can be provided to reduce or prevent out-of-plane buckling: (a) Lateral restraint, which prevents lateral movement of the compression flange. (b) Torsional restraint, which prevents rotation of a member about its longitudinal axis. (c) Intermediate lateral restraint to the tension flange. Such restraints are only of limited benefit, but do modify the out-of-plane buckling mode and may therefore allow the distance between torsional restraints to be increased. As shown in Figure 6.3, practical details may provide more than one type of restraint.