Hydroelastic response analysis of pneumatically supported floating structures using a BEM-FEM coupling method

Pneumatically supported floating structures, which utilize an aircushion below the structural bottom, have been suggested to remedy the excessive hydroelastic response of the conventional pontoon-type floating structures. This paper presents an analytical study to examine the hydroelastic responses of the pneumatically supported floating structures. For the hydroelastic analysis, the fluid is modeled as a 2D-strip of finite depth seawater whereas the floating structure is modeled as a beam with zero-draft. A direct coupled model is then constructed by using the boundary integral formulation for the fluid and FEM for the structure and by incorporating a pneumatic factor at the fluid-structure interface to consider the compressibility of the aircushion. For case studies, hydroelastic responses of the pneumatically supported type are compared to those of the pontoon-type for a wide range of pneumatic factors and regular waves. It is shown that the pneumatic supports can significantly reduce the hydroelastic responses in general and that the response reduction may be greatly enhanced when the pneumatic factor is chosen as small as possible for a relatively short incident wave. This study demonstrates that the analytical technique proposed herein can be used to examine the design conditions which are essential for practical applications of the pneumatically supported floating structures.