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ii iii In connections of steel structures stress concentrations occur due to the rapid geometric changes in the cross section. If the material has sufficient ductility then, due to plastic deformations, forces are redistributed so there will be equilibrium in the internal forces. In design codes this is accounted for by imposing certain requirements with respect to the tensile/yield strength ratio and minimal strain at fracture. This problem is of particular importance when high strength steels are used as questions are raised related to their ductility capacity. Over the past decades, high strength steel has gained significant ground in the steel structures market. A steel grade such as S355, which was considered to be a high strength steel 20 years ago, is now one of the predominant grades used for steel construction. In practice the occurrence of stress concentrations raises questions on how to deal with them and how to ensure a certain amount of ductility to avoid brittle fracture. In most cases an inelastic finite element analysis in shell elements and based on the nonlinear behaviour of the materia