1. Ph.D. Student, Civil and Environmental Engineering, Univ. Politècnica de Catalunya, Campus Diagonal Nord, Edifici C1, C. Jordi Girona 1, 1-3 08034 Barcelona, Spain (corresponding author).
2. Professor, Civil and Environmental Engineering, Univ. Politècnica de Catalunya, Campus Diagonal Nord, Edifici C1, C. Jordi Girona 1, 1-3 08034 Barcelona, Spain.
3. Professor, Dept. of Civil Engineering, City College of New York/CUNY, Steinman Hall, 160 Convent Ave., New York, NY 10031.