1. School of Transportation Southeast Univ., Nanjing, 210096, P. R. China.School of Transportation Southeast Univ., Nanjing, 210096, P. R. China.
2. Dept. of Civil Engineering, The Catholic Univ. of America, 620 Michigan Ave., N. E., Washington, DC 20064 (corresponding author).
3. Dept. of Civil Engineering The Catholic Univ. of America, 620 Michigan Ave., N. E., Washington, DC 20064.