About the seismic return period: a simplified algorithm

In many countries, seismic-hazard maps were adopted. These maps allow to evaluate the elastic spectrum shape which defines the reference seismic action. The verification of the seismic vulnerability of existing structures by nonlinear methods allows to evaluate the seismic demand starting right from the spectral shapes. However, it is not quite immediate the assessment of the return period of the seismic action corresponding to the actual structural capacity (i.e. the maximum displacement at each limit state). This paper proposes a simplified algorithm for the evaluation of the seismic return period corresponding to the actual capacity of the structure. The structural response, as capacity curve, is defined once only known the elastic stiffness, yield and ultimate displacement at the prefixed limit state. The methodology was validated by means the comparison between the periods obtained with the proposed algorithm and the pushover analysis on a reinforced concrete existing building.