1. Senior Researcher, Highway and Transportation Research Division, Korea Institute of Civil Engineering and Building Technology, Goyang 411-712, Republic of Korea.
2. Senior Researcher, Highway and Transportation Research Division, Korea Institute of Civil Engineering and Building Technology, Goyang 411-712, Republic of Korea (corresponding author).
3. Assistant Professor, College of Engineering, Architecture and Technology, Oklahoma State Univ., Stillwater, OK 74078.