1. Postdoctoral Fellow, ESCER Centre, Univ. of Quebec at Montreal, 201 Ave., President-Kennedy Montreal PQ, Canada H2X 3Y7.
2. Associate Professor, Department of Civil and Environmental Engineering, Seoul National Univ., 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea (corresponding author).
3. Professor and Head, Dept. of Civil and Environmental Engineering, Univ. of Massachusetts Amherst, 224 Marston, Amherst, MA 01003.