1. Associate Professor, Dept. of Civil, Environmental, and Architectural Engineering, Univ. of Colorado, 1111 Engineering Dr., ECOT 441, UCB 428, Boulder, CO 80309 (corresponding author).
2. Associate Professor, Dept. of Civil Engineering, Campus Box 113, P.O. Box 173364, Univ. of Colorado Denver, Denver, CO 80217-3364.