1. Associate Professor, School of Civil and Environmental Engineering, Nanyang Technological Univ., Nanyang Ave., Singapore 639798 (corresponding author).
2. Associate Professor, Dept. of Civil Engineering, National Univ. of Singapore, Blk E1A, No. 07-03, 1 Engineering Dr. 2, Singapore 117576.
3. Professor, School of Civil and Environmental Engineering, Cornell Univ., Hollister Hall, Ithaca, NY 14853-3501.