1. Professor, Dept. of Civil Engineering, Meijo Univ., Nagoya 468-8502, Japan (corresponding author).
2. Japan Society for the Promotion of Science Research Fellow, Dept. of Civil Engineering, Meijo Univ., Nagoya 468-8502, Japan.
3. Kobe Shipyard and Machinery Works, Mitsubishi Heavy Industries, Ltd., 1-1-1 Wadasaki-cho, Hyogo-ku, Kobe 652-8585, Japan.