1. Research Fellow, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, 1 Engineering Dr. 2, Singapore 117576, Singapore.
2. Research Fellow, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, 1 Engineering Dr. 2, Singapore 117576, Singapore (corresponding author).
3. Research Fellow, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, 10 Dover Dr., Singapore 138683, Singapore; presently, Assistant Professor, Singapore Institutive of Technology, 10 Dover Dr., Singapore 138683, Singapore.
4. Professor, Dept of Civil and Environmental Engineering, National Univ. of Singapore, 1 Engineering Dr. 2, Singapore 117576, Singapore.