1. Assistant Professor, Dept. of Engineering Sciences, Middle East Technical Univ., 06531 Ankara, Turkey; formerly, PhD, Dept. of Civil, Environmental, and Architectural Engineering, Univ. of Colorado, Boulder, CO 80309-0428.
2. Professor, Dept. of Civil, Environmental, and Architectural Engineering, Univ. of Colorado, Campus Box 428, Boulder, CO 80309-0428 (corresponding author).