MPS法による大型船舶の津波中挙動と構造物に作用する衝突荷重特性に関する研究

Abstract

Most of the loss suffered in the Great East Japan Earthquake was due to the tsunami rather than to the earthquake itself. An unusual aspect of these disasters was that much of the structural wreckage that was swept up by the tsunami remained and drifted on the sea. Some of the wreckage caused subsequent damage to coastal structures. These drifting objects caused by the tsunami included containers, boats and ships, cars, caissons, and other objects from the harbors. Thus, it is necessary to solve these problems in order to plan the safe coastal zone. However, there is no effective method in order to verify this subject, and few reports are available on characteristics of collision behavior of huge ship in tsunami. These problems can be resolved by the hydraulic model experiment. However, it is difficult to verify the scale model experiment, in addition these need enormous cost. On the other hand, numerical simulation method is suitable for analyze the collision phenomena of huge ship in tsunami. The MPS method is a particle based method originally proposed by Koshizuka et al. and is a Lagrangian procedure for simulating a flow field employing the moment-to-moment motions of particles distributed in a space. The most distinctive aspect of particle methods is that they do not require consideration of connections between calculation points. Because of this, the MPS method is well suited for analysis of strongly non-linear phenomena accompanying large deformations of free surfaces. The objective in this paper is following items, 1) to propose and evaluate the friction elastic body model for collision phenomena using MPS method, 2) to clarify characteristics of collision behavior of huge ship. The present numerical model of the MPS method is applied the dynamic analysis of elastic solids developed by Koshizuka et al. And, the authors approach the new method of the MPS which can analisys friction phenomena between solid in this research. As these results, the authors found that present model is suitable for calculation of collision phenomena through the verifications of the wave tank experiment and the analytical solution. In addition, the authors confirmed basic characteristics of behavior of collision phenomena of huge ship in tsunamis. Further, it was concluded that, the impulse due to collision force without friction force on the surface of the huge ship is 55% larger than the impulse of only tsunami waves in case of reflection tsunami flow from the land structure is small.