1. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., Tainan 701, Taiwan, R. O. C. E-mail: fanglou@mail.ncku.edu.tw
2. Doctoral Candidate, Dept. of Civil Engineering, National Cheng Kung Univ., Tainan 701, Taiwan, R. O. C.
3. Formerly, Graduate Student, Dept. of Civil Engineering, National Cheng Kung Univ., Tainan 701, Taiwan, R. O. C.