1. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., No. 1, Ta-Hsueh Rd., Tainan, Taiwan, Republic of China (corresponding author).
2. Graduate Student, Dept. of Civil Engineering, National Cheng Kung Univ., No. 1, Ta-Hsueh Rd., Tainan, 70101, Taiwan, Republic of China.