1. Res. Engr., Port and Airport Res. Inst., Independent Administrative Institution, 3-1-1 Nagase, Yokosuka 239-0826, Japan. E-mail: tarek@ cc.phri.go.jp
2. Prof., Facu. of Engrg., Tokyo Inst. of Technol., 2-12-1 O-okayama, Meguro-ku, Tokyo 152, Japan.
3. Assoc. Prof., Niigata Univ., 8050 Ikarashi 2-no-cho, Niigata-shi, Niigata 950-2181, Japan.
4. Engr., Obayashi Inc., Takaishi Shi, Takasago 3-1, Osaka 592-0001, Japan.