1. School of Civil Engineering and Architecture, Central South Univ., Changsha, Hunan, 410075 CN.
2. Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931-1295, US
3. Ph.D., P.E., Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931-1295, US (Corresponding author), e-mail: zyou@mtu.edu
4. Ph.D., School of Civil Engineering and Architecture, Central South Univ., Changsha, Hunan, 410075 CN.
5. Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931-1295, US.
6. Ph.D., P.E., Civil Engineering, Western Transportation Institute, Montana State Univ., Bozeman, MT 59717-4250, US, e-mail: Xianming_s@coe.montana.edu
7. Ph.D., Research Assistant Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634, US, e-mail: Wingar2@clemson.edu