1. Professor, Civil Engineering Dept., National Chung-Hsing Univ., 250 Kuo-Kwan Rd., Taichung 402, Taiwan, R.O.C.
2. Ph.D. Candidate, Civil Engineering Dept., National Chung-Hsing Univ., 250 Kuo-Kwan Rd., Taichung 402, Taiwan, R.O.C. (corresponding author).
3. Ph.D. Candidate, Civil Engineering Dept., National Chung-Hsing Univ., 250 Kuo-Kwan Rd., Taichung 402, Taiwan, R.O.C.