1. DiBT Dept., Structural and Geotechnical Dynamics Laboratory StreGa; University of Molise; Viale Manzoni snc 86100 Campobasso Italy
2. Engineering Dept.; University of Sannio; Piazza Roma 21 82100 Benevento Italy
3. Dept. of Structures for Engineering and Architecture; University of Naples “Federico II”; Via Claudio 21 80125 Naples Italy