VIVA modes files

The VIVA input files that are exported from OrcaFlex specify that transverse mode frequencies, shapes and curvatures are supplied in files freq.in, modes_us.in and curv_us.in. These files are created by an OrcaFlex modal analysis. The procedure for selecting transverse modes is identical to that used for SHEAR7.

Because VIVA requires an equally-spaced discretisation of the line, the mode shapes and curvatures files may be interpolated from the original OrcaFlex modes which reflect the OrcaFlex model discretisation. This discretisation of the data supplied to VIVA is determined by the number of points specified on the VIVA data form. For the calculation to be accurate both the OrcaFlex model discretisation and the equally spaced discretisation used by VIVA must be sufficiently fine to capture the modes that are important to the VIVA analysis.