1. Ph.D. Candidate, Highway School, Chang’an Univ., Xi’an, Shaanxi 710064, China. .
2. Professor, Highway School, Chang’an Univ., Xi’an, Shaanxi 710064, China (corresponding author). .
3. Professor, School of Civil Engineering, Univ. College Dublin, Dublin D02 PN40, Ireland. .
4. Highway School, Chang’an Univ., Xi’an, Shaanxi 710064, China.