1. Structural resistance to instability

Regulatory checks on instability limit states, which are classified as ultimate limit states, use scientifically and technically sound procedures covering basic instability phenomena. However, they use approximate interaction relationships when two or more of these phenomena are likely to coexist.

In the series of articles devoted to instabilities, the emphasis is placed much more on concepts than on mathematical developments. The aim of these articles is not to constitute a treatise on stability, or rather instability, but to bring together the elements of knowledge useful for a physical and rational understanding of the rules that govern phenomena of instability.