Three-Dimensional Time-Domain Analysis of Very Large Floating Structures Subjected to Unsteady External Loading

The strong interest in very large floating structure (VLFS) is a result of a need to utilize effectively the ocean space for transportation, industrial use, storage, habitats, and military bases, among others. The VLFS has great width and length and relatively small flexural rigidity, therefore, investigation of its hydroelastic behavior including fluid-structure interaction is of greater importance than studies of its motion as rigid bodies. In addition to the most important wave-induced responses, the operation of the VLFS also requires determination of its dynamic responses with respect to the effect of unsteady external loading due to intense traffic, load movement, takeoffs and landings of airplanes, missile takeoffs, etc. Therefore, the transient responses of a VLFS to impulsive and moving loads must be studied by a reliable calculation method. In this study, a finite element procedure developed directly in time domain for solution of transient dynamic response of the coupled system consists of a VLFS and a fluid domain subjected to arbitrary time-dependent external loads is presented. The hydrodynamic problem is formulated based on linear, inviscid, and slightly compressible fluid theory and the structural response is analyzed under the thin plate assumption. For numerical calculations, a scaled model of the Mega-Float is exemplified. Three tests—weight pull-up test, weight drop test, and weight moving test which idealize the airplane landing and takeoff—are carried out and compared with published experimental data. The overall agreement was favorable which indicates the validation of the present method.