ABSTRACT
Steel structures in seismic zones are designed for stiffness, strength and ductility. Stiffness is required for the limitation of damage of non-structural elements and reduction of 2nd order effects. Strength is required for the safe transmission of the acting forces and moments. Ductility under cyclic loading leads to the dissipation of the input seismic energy and results in a reduction of the seismic forces. The demand for strength is therefore closely connected to the provision of ductility. The latter may result in a considerable reduction of the acting seismic forces by a factor of up to 6, according to Eurocode 8 (2004). Not the entire structure shall exhibit uncontrollable inelastic deformations during a strong earthquake. Such deformations are associated with damage and shall be limited to specific zones, the dissipative zones. For that reason, the elements of the dissipative zones are weaker than their connections and the adjacent members. The latter are designed for higher forces and moments according to capacity design criteria.
