1. Structural resistance to instability

Regulatory verification of instability limit states, which are classified as ultimate limit states, calls for scientifically and technically sound procedures covering elementary instability phenomena. When two or more of these phenomena are likely to coexist, however, they are based on approximate interaction relationships.

In the series of dossiers devoted to instabilities, the emphasis is on concepts rather than mathematical developments. Indeed, the aim of these dossiers is by no means to constitute a treatise on stability, or rather on instability, but to bring together the elements of knowledge useful for a physical and rational understanding of the rules governing instability phenomena.