  The additional signals observed in the frequency spectra of the
first-overtone RR Lyrae stars, that form a period ratio around 0.61 with the
period of the first overtone, are a common phenomenon for RRc and RRd stars, as
well as for first-overtone classical Cepheids. The recently proposed model
explains these signals as harmonics of non-radial modes of degrees 8 or 9 in
the case of RR Lyrae stars and 7, 8, or 9 in the case of classical Cepheids. We
selected at least triple-mode RR Lyrae stars pulsating in radial and non-radial
modes for asteroseismic modeling. We assume the identification of the
non-radial modes as predicted by the model. We calculated a dense grid of
models for RR Lyrae stars using envelope pulsation code. By matching first
overtone period and period ratios we obtained physical parameters for the
selected sample of triple-mode stars. It is the very first attempt of modeling
RR Lyrae stars with non-radial modes. We compared our results with predictions
of stellar evolution theory, which resulted in a mass discrepancy more
noticeable for long-period stars: pulsation masses seem higher than
evolutionary masses. We compared metallicity estimates for RRc stars from
modeled sample with metallicities determined spectroscopically for a sample of
RRc stars in the solar neighbourhood: both distributions are consistent.
