1. Associate Professor, College of Civil Engineering, Hunan Univ., Changsha, Hunan 410082, China; formerly, Research Fellow, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798 (corresponding author).
2. Associate Professor, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798.