1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., 200 Patton Hall, Blacksburg, VA 24060 (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., 200 Patton Hall, Blacksburg, VA 24060.
3. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., 200 Patton Hall, Blacksburg, VA 24060.