1. Associate Professor, Dept. of Marine and Mechanical Engineering, Naval Academy, 669 Junxiao Rd., Zuoying District, Kaohsiung 813, Taiwan.
2. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., 1 Univ. Rd., Tainan 701, Taiwan (corresponding author).
3. Graduate Research Assistant, Dept. of Civil Engineering, National Cheng Kung Univ., 1 Univ. Rd., Tainan 701, Taiwan.