Modeling, analysis and design of steel connections between structural members are of primary importance in structural steel design, because the connections' behavior significantly affects the response of steel structures under monotonic loading conditions, both in elastic and in plastic range, and exceptional impact loading conditions. In addition, also the seismic response of steel structures is strongly affected by the ultimate behavior of structural connections under cyclic loading conditions [1-3]. In particular, seismic design of steel structures is commonly carried out to assure the dissipation of the seismic input energy in the so-called "Dissipative Zones" which has to be properly detailed in order to assure wide and stable hysteresis loops. Once the yielding of non-dissipative structural members is avoided, connections play a role of paramount importance. In fact, they can be designed either as Full Strength (FS) or Partial Strength (PS). In the first case, the seismic input energy is dissipated by means of plastic cyclic excursions in structural members. In the second case, dissipation requires the plastic engagement of ductile connection components.