Extension of the hybrid force/displacement (HFD) seismic design method to 3D steel moment-resisting frame buildings

The hybrid force/displacement (HFD) seismic design method for planar steel frames developed by the authors is extended to 3D steel buildings using moment-resisting frames. HFD combines the advantages of both the displacement-based and the force-based seismic design methods and reduces or eliminates their disadvantages. An extensive response databank is developed through nonlinear dynamic analyses on 38 steel space frames designed according to Eurocodes 3 and 8 and subjected to 42 pairs of earthquake ground motions. This response databank is then utilized for the development of empirical formulae providing the behavior factor as a function of the geometrical and dynamic characteristics of the building, including its accidental eccentricity, as well as the target maximum interstorey drift ratio and local ductility. Thus, the proposed seismic design method, eventhough works as a force-based design one, controls structural and non-structural damage through the use of a behavior factor which is a function of seismic deformation demands. Numerical examples are presented to illustrate the proposed method and demonstrate its merits over the force-based seismic design method of Eurocode 8.