1. Associate Professor, Dept. of Civil Engineering, National Taipei Univ. of Technology, 1, Sec. 3, Chung-Hsiao E. Rd., Taipei, Taiwan 106, Republic of China (corresponding author).
2. Assistant Professor, Dept. of Civil Engineering, National Taipei Univ. of Technology, 1, Sec. 3, Chung-Hsiao E. Rd., Taipei, Taiwan 106, Republic of China.
3. Professor, Dept. of Civil and Environment Engineering, West Virginia Univ., Morgantown, WV 26506.