Nowadays, the seismic-resistant structural design is conducted using a set of code prescriptions that allows to reach a consistent behavior. Analysis procedures are carried out considering elastic behavior, applying behavior factors in order to obtain equivalent seismic forces. From the displacements of the elastic analysis it is possible to calculate the inelastic ones by means of amplification factors usually based on the behavior factors; however, it can be observed a high variability of these factors that the seismic codes prescribe. In this work, a new procedure of seismic sizing based on non linear analysis is presented. The procedure is applied to design a set of regular RC framed buildings with different heights, for high seismic hazard level. The seismic capacity of the buildings is assessed through a set of Limit States. Results shows that the new procedure is suitably in order to do a seismic sizing of structures, providing the designer assessment criteria in accordance with the buildings characteristics and the seismic hazard.