1. Research Professor, Dept. of Civil Engineering, Chungnam National Univ., Daejeon 34134, Republic of Korea (corresponding author).
2. Director of Research, Modjeski and Masters, Inc., 100 Sterling Pkwy., Mechanicsburg, PA 17050.
3. Distinguished Professor, Dept. of Engineering Science and Mechanics, Pennsylvania State Univ., University Park, PA 16802.