In modern seismic design, the codes admit explicitl y incursions of the structures within the rank of i nelastic behavior, but due to the existing difficulty to make the nonlinear analysis in the process of buildings assessments, elastic analysis is allowed, with seismic forces re duced by means of response reduction factors, this factors are known as ‘R factors’. The application of this proc edure has been widely accepted, since the structure s calculated under these resultant seismic forces have demonstra ted a good performance during the occurrence of str ong earthquakes during the two past decades. Nevertheless, t he determination of the response reduction factors depends on from its initial formulation, the expert’s criterio n, statistic analysis or the engineer’s opinion. In this work, we