LOCAL STRUCTURAL ANALYSIS OF LARGE FLOATING STRUCTURES BY USING DIRECT FORCE METHOD

Very Large Floating Structure (VLFS : MEGA FLOAT) of several thousand meters long are being considered for various applications such as floating airplanes and so on. The MEGA FLOAT recently designed as a thin mat-like configuration and very large horizontal area. Therefore this type of structure is very flexible and the elastic deformation due to wave forces is more critical than the rigid body motions.Recent investigation of hydro-elastic response analysis of MEGA FLOAT have been much improved, the behavior of structural body induced by the wave force have been cleared.From those results of hydro-elastic response analysis, global and generous stress distribution have been able to estimated, however detail analysis can not be estimated directly because it is difficult to solve full scale structural model. Since there are many discontinuous and stress concentrated positions in the structure of multi-purpose MEGA FLOAT, we proposed the detail structure by using phase structural analysis method applied the results of hydro-elastic response analysis to the detail local structure.This paper introduce one of the orthodox methods of the phase structural analysis method by the zooming technique of FEM structural analysis. We show the calculation method for the structural zooming model which is applied to the forces from the hydro-elastic response analysis, and the results and consideration for the few examples of the detail structure of MEGA FLOAT.