An analytical description of the behaviour of a connection has to cover all sources of deformabilities, local yielding, local instabilities, etc. Due to the multitude of influencing parameters, a macroscopic inspection of a complex connection - by subdividing it into components - has proved to be most appropriate. This is the approach recently proposed by the Eurocode 3. One of the basic components is the equivalent T-stub, which adequately models several parts of a connection: column flange in bending, end plate in bending and flange cleat in bending. Reliability techniques combined with non-linear analysis of structures have been applied to interpret the effects of parameter variability on the T-stub behaviour. Simplified safety rules are derived from this probabilistic high-level approach.