Some basic principles for semi-rigid concept

Publisher Summary This chapter provides overview of some basic principles for semi-rigid concept. Obtaining moment-rotation curves from a reasonable process is presented as one of the key parameter. Aside the experimental way several mechanical or physical models are developed. It appears that finite element method, used at various scales, is able to bring satisfying results as far as computing costs are dropping down. Various scales mean various levels of geometrical description and meshing: local, semi-local as the so-called components method, or global. The interest and the potential capabilities of each description are discussed. Most of the present regulation codes regarding constructional steelwork allow for the semi-rigid concept as model for connection behavior. Numerous examples have shown the interest of such a modelization in terms of economy but also in terms of safety in the case of seismic action.