2. Types of elastic instability

When loading a structure – it will often be an elastic structural element – and its behavior can be examined using a load-displacement diagram. The load is obviously that applied to this structure. As for the displacement, it is the displacement of a reference point chosen a priori. In practice, this point is chosen because a significant displacement value is expected there.

When the load is applied incrementally from zero, the load-displacement relationship described constitutes an equilibrium trajectory. The instability of the structure corresponds to the transition, on this trajectory, between stable and unstable equilibrium configurations. This instability occurs through the appearance of:

• a bifurcation of equilibrium (Figure 2...