1. Graduate Research Associate, Dept. of Civil and Environmental Engineering, Vanderbilt Univ., VU Station B 351831, Nashville, TN 37235.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Vanderbilt Univ., VU Station B 351831, Nashville, TN 37235 (corresponding author). E-mail: eugene.j.leboeuf@vanderbilt.edu