1. Associate Professor, Civil Engineering Dept., National Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 119260 (corresponding author).
2. Professor, Civil Engineering Dept., National Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
3. Postgraduate Student, Civil Engineering Dept., National Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 119260.