1. Guangzhou Expressway Co., Ltd., 1800 S. Guangzhou Rd., Guangzhou, Guangdong 510288, China; formerly, Graduate Student, Univ. of Tennessee, Knoxville, TN 37996.
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Tennessee, Knoxville, TN 37996 (corresponding author).
3. Research Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Tennessee, Knoxville, TN 37996.
4. Assistant Professor, College of Civil and Transportation Engineering, South China Univ. of Technology, Guangzhou 510641, China.