1. Research Professor, School of Civil and Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea.
2. Associate Professor, Civil, Structural and Environmental Engineering, State Univ. of New York at Buffalo, 233 Jarvis Hall, Buffalo, NY 14260; presently, Professor, Dept. of Civil Engineering, National Taiwan Univ., Taipei 10617, Taiwan (corresponding author).
3. Professor, School of Civil and Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea.