The structure of a Swath ship can be analyzed by the hydro-elastic, rigid-dynamic and quasi-static approaches. These are standard methods used in the industry and academic research. Through a numerical model of an actual Swath ship design, the present paper provides a comparative study of these methods and discusses their applicability. The deflections and stresses evaluated from the three methods are compared. Hydro-elastic effects are shown to be more important in certain areas where the structure is more flexible.
Accurate predictions of structural stress and deformation in Swath ships assumes greater importance as recent designs involve more advanced applications and lighter construction. The inherent geometry of Swath ships and the need for a lightweight construction yield a more flexible structure than generally found in conventional ships. When subject to oscillatory loading, a Swath ship might exhibit structural vibrations in addition to the rigid-body response. Excessive vibrations can be objectionable to passengers, but most importantly can lead to fatigue failure of the structure. The design and operational experience of a Swath ship is presented by Seidl et al. (1993). In general, the structural stress and deformation in a Swath ship can be evaluated by the hydro-elastic, rigid-dynamic and quasi-static approaches. The Concept of hydro-elasticity was introduced in the late 1950"s by analogy to aero-elasticity (e.g., Flax, 1960; and Heller, 1964). The method received more attention in marine dynamics after the work of Bishop and Price (1979) and Wu (1984), and has been used in a number of recent research projects involving flexible floating structures (e.g., Reane et al., 1991; Ertekin et al., 1993; and Newman, 1994). In the hydro-elastic approach, both the structural and rigidbody responses are included in the evaluation of the hydrodynamic and inertia forces.