1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Yonsei Univ., Seoul 120-749, South Korea.
2. Professor, Dept. of Civil and Environmental Engineering, Yonsei Univ., Seoul 120-749, South Korea (corresponding author).
3. Research Fellow, Construction Management Division, Construction and Economy Research Institute of Korea, Seoul 135-701, South Korea.
4. Associate Professor, Dept. of Civil, Construction, and Environmental Engineering, Iowa State Univ., 326 Town Engineering, Ames, IA 50011.