1. Graduate Research Assistant, Civil and Environmental Engineering, Univ. of Houston, Houston, TX 77004.
2. Assistant Professor, Sonny Astani Dept. of Civil and Environmental Engineering, Univ. of Southern California, 3620 S. Vermont Ave., KAP 210, Los Angeles, CA 90089-2531 (corresponding author).
3. Associate Professor, Civil and Environmental Engineering, Univ. of Houston, Houston, TX 77004.