Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 66 Where the internal columns provide significant stiffness, it is uneconomic to ignore them and a detailed analysis of the entire frame by software would be preferable. 13.4 Snap through instability Figure 13.4 Snap through instability As shown in Figure 13.4, the reduced sway stiffness of frames with three or more bays may lead to snap through instability of an internal bay. Such structures may be checked with appropriate software to ensure satisfactory behaviour. Appendix B may be used to calculate an estimate of the sensitivity to snap through. 13.5 Design summary  Many aspects of behaviour of multi-bay portal frames are similar to single bay frames  Special consideration should be given to the sway stability and snap through stability of multi-bay frames.