1. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., 1 University Rd., Tainan 701, Taiwan (corresponding author).
2. Graduate Student, Dept. of Civil Engineering, National Cheng Kung Univ., 1 University Rd., Tainan 701, Taiwan.
3. Engineer, Sinotech Engineering Consultants, Ltd., 8F, 171, Sec. 5, Nanking E. Rd., Taipei 10570, Taiwan.