1. Staff Project Professional, Fugro Consultants, Inc., 6100 Hillcroft Ave., Houston, TX 77081.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Waterloo, Waterloo, ON, Canada N2L 3G1 (corresponding author).
3. Professor, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47907.