1. School of Civil and Environmental Engineering, Oklahoma State University , 207 Engineering S, Stillwater, OK 74078-5031 , United States
2. School of Civil Engineering, Southwest Jiaotong University , No. 999, Xi'an Road, Pidu District, Chengdu, Sichuan 611756 , P. R. China
3. Railway Engineering Research Institute, China Academy of Railway Science Corporation Limited , No. 7, Daliushu Rd, Haidian District, Beijing 100082 , China