def displacement_from_effective_period(eta, corner_disp, t_eff, corner_period):
    """
    Displacement of SDOF using displacement-based assessment. # Eq. 11 Millen et al. (2016)
    :param eta: Displacement reduction factor
    :param corner_disp: Corner spectral displacement
    :param t_eff: Effective displacement
    :param corner_period:
    :return:
    """
    if t_eff > corner_period:
        return eta * corner_disp
    return eta * corner_disp * t_eff / corner_period
