1. Former Graduate Student, Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, KR.
2. Engineer, Civil and Environment Division, POSCO Engineering & Construction Co., Ltd., Pohang, 790-704, KR.
3. Professor, Dept. of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, KR (Corresponding author), e-mail: gyechun@kaist.edu