I would like to confirm if the results of the Inelastic Displacement Spectra corresponds to "yield-deformations response spectrum (u_y)" or to "pick deformations (u_m)" of inelastic system. (where ductility = u_m/u_y).
I have compared my calculations of inelastic spectra (according Chopra's book) and I find a difference with SEISMOSPECT exactly of target ductility's magnitude. So maybe SEISMOSPECT achieve u_m instead of u_y.
I find too a little difference between the Inelastic Acceleration Spectra, but it is not proportional to the ductility... same question. Is this acceleration associated to yield-deformation or to pick-deformation of inelastic system?
Thank you for any comment.