1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061 (corresponding author). E-mail: lzh@vt.edu
2. Graduate Research Assistant, Dept. of Engineering Science and Mechanics, Virginia Tech, Blacksburg, VA 24061. E-mail: pkm2004@vt.edu
3. Associate Professor, Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061. E-mail: tcousins@vt.edu
4. Professor, Dept. of Engineering Science and Mechanics, Virginia Tech, Blacksburg, VA 24061. E-mail: jlesko@vt.edu