1. Professor, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti, 93, 06125 Perugia, Italy (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti, 93, 06125 Perugia, Italy.
3. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Perugia, Via G. Duranti, 93, 06125 Perugia, Italy.