1. Senior Research Instructor, Dept. of Civil Engineering, Univ. of Colorado Denver, Denver, CO 80217; and Lecturer, Dept. of Structural Engineering, Cairo Univ., Cairo, Egypt.
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801 (corresponding author).
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana Champaign, Urbana, IL 61801.