Dual Craig-Bampton with enrichment to avoid spurious modes

The dual Craig-Bampton method can suffer from the fact that the reduced system has negative eigenvalues. Those negative eigenvalues are related to modes with weak interface compatibility and can be present in the lower frequency range when the reduction space is too poor. In this paper we investigate is so-called Modal Truncation vectors related to the interface forces can be used in the reduction basis as an attempt to reject the spurious modes with negative eigenvalues to a higher frequency range. In this work we describe how the modal truncation modes can be incorporated in the Dual Craig-Bampton method and show on a numerical example that they have the potential of mitigating the problem of negative eingenvalues and to improve the quality of the reduction basis.