1. Research Student, Dept. of Civil Engineering, National Univ. of Singapore, Singapore.
2. Senior Research Engineer, ExxonMobil Upstream Research Company, Houston, TX 77252; formerly, Assistant Professor, Dept. of Civil Engineering, National Univ. of Singapore, Singapore (corresponding author).
3. Retired; formerly, Professor, Dept. of Civil Engineering, National Univ. of Singapore, Singapore.