1. Postdoctoral Researcher, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti 93, 06125 Perugia, Italy.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti 93, 06125 Perugia, Italy.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Northeastern Univ., 400 Snell Engineering Center, 360 Huntington Ave., Boston, MA 02115 (corresponding author).
4. Full Professor, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti 93, 06125 Perugia, Italy.