1. Professor, School of Civil Engineering, Qingdao Univ. of Technology, Qingdao 266000, China.
2. Graduate Student, School of Civil Engineering, Qingdao Univ. of Technology, Qingdao 266000, China.
3. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802 (corresponding author).
4. Engineer, China Energy Baoshen Railway Group Co., Ltd., No. 1 Arding St., Baotou 014010, China.