ABSTRACT
Steel structures in seismic zones are designed for stiffness, strength and ductility. Stiffness is required for limitation of damage of non-structural elements and reduction of the 2nd order effects. Strength is required for a 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 the European and 12 according to the American Codes.
