1. Dept. of Civil and Environmental Engineering, Thornton Hall B228, Univ. of Virginia, 351 McCormick Rd., Charlottesville, VA 22904-4742.
2. Dept. of Civil and Environmental Engineering, Thornton Hall B228, Univ. of Virginia, 351 McCormick Rd., Charlottesville, VA 22904-4742 (corresponding author).