1. Professor, Dept. of Civil Engineering, National Chung Hsing Univ., Taichung 402, Taiwan (corresponding author).
2. Senior Graduate Student, Dept. of Civil Engineering, National Chung Hsing Univ., Taichung 402, Taiwan.
3. Professor, Dept. of Civil Eng., Indian Institute of Technology, Kharagpur 721302, West Bengal, India.