1. Research Professor, School of Civil, Environmental, and Architectural Engineering, Korea Univ., 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea.
2. Research Director, Korea Expressway Corporation Research Institute, Dongbu-daero 922beon-gil, Dongtan-myeon, Hwaseong 445-812, Korea.
3. Professor, School of Civil, Environmental, and Architectural Engineering, Korea Univ., 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea (corresponding author).