1. Associate Professor, Dept. of Civil and Environmental Engineering, Hanbat National Univ., Daejeon 136-702, South Korea.
2. Assistant Professor, School of Architecture, Kyungnam Univ., Changwon-si, Gyeongsangnam-do 631-701, South Korea.
3. Associate Professor, Dept. of Civil Engineering, Konkuk Univ., Seoul 143-701, South Korea (corresponding author).