1. Research Student, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798, Singapore.
2. Associate Professor, School of Civil and Environmental Engineering, Nanyang Technological Univ., 50 Nanyang Ave., Singapore 639798, Singapore (corresponding author). E-mail: ctcfung@ntu.edu.sg
3. Associate Professor, Dept. of Civil Engineering, The Univ. of Hong Kong, Pokfulam Rd., Hong Kong. E-mail: young@hku.hk