Calculation of wave propagation in rib-stiffened plate structures

In this work, wave propagation in structural waveguide systems is analyzed. For this purpose a semi-analytical finite element technique has been adapted and further developed. With this technique, the dispersion properties of waveguide structures built up of thin-walled finite strip elements can be calculated. The method is applied to analyze wave propagation in rib-stiffened plate structures typical of ship construction, providing a detailed understanding of the nature of waves propagating in such waveguide systems. The results from this analysis show that flexural waves propagating in such structures can be divided into subgroups with respect to which parts of the structure determine the wavenumbers associated with the propagation. It is shown that in the low frequency region the wavenumbers may be approximated by applying so-called equivalent plate theory, in which the built-up plating is represented by an equivalent orthotropic plate. Also, at higher frequencies the wavenumbers of most flexural modes in a frequency region just above the cut-on frequency, may be estimated by applying equivalent plate theory. (C) 1996 Academic Press Limited