Instability of symmetric structural systems with independent loading parameters
The general post-critical characteristics of a discrete structural system with independent loading parameters are studied. Attention is restricted to elastic conservative systems which satisfy certain analytical symmetry conditions and which lose their initial stability at a 'symmetric special' critical point. The results are compared with Koiter's 'stable symmetric' and 'unstable symmetric' bifurcation points, and three theorems are established. A shallow circular arch under the action of a set of external loads which can be represented by two independent parameters is analysed to illustrate some aspects of the theory.