1. Architect, Dept. of Architectural Sciences, Univ. of Genoa, 16123 Genoa, Italy.
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Pisa, 56126 Pisa, Italy (corresponding author).
3. Full Professor, Dept. of Civil Engineering, Univ. of Pisa, 56126 Pisa, Italy.