Keyword: missing mass, prestress, PSD Missing mass doesn’t support linear perturbation based on nonlinear structural analysis (e.g., large deflection, frictional contact…). Removing all nonliearity in static structural will enable missing mass work. If you would like to include nonlinear prestress, a workaround to account for truncated modes is to use residual vector. See solution #2042955 for example of residual vectors in PSD analysis