1. Faculty of Civil Engineering and Mechanics, Kunming Univ. of Science and Technology, Kunming, Yunnan, 650500, China (corresponding author).
2. Faculty of Civil Engineering and Mechanics, Kunming Univ. of Science and Technology, Kunming, Yunnan, 650500, China.
3. School of Engineering, Univ. of Bradford, Richmond Rd., Bradford BD7 1DP, UK.