1. Postdoctoral Researcher, Stanford Univ., Dept. of Civil and Environmental Engineering, Y2E2 Building, 473 Via Ortega, Stanford, CA 94305-4020 (corresponding author).
2. Professor, Stanford Univ., Dept. of Civil and Environmental Engineering, Y2E2 Building, 473 Via Ortega, Stanford, CA 94305-4020.
3. Professor em., Ruhr-Univ. Bochum, Dept. of Civil and Environmental Engineering, Universitaetsstr. 150, D-44801 Bochum, Germany.