1. Full Prof., Dept. of Civ. Engrg., Univ. of Salerno, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy.
2. Full Prof., Dept. of Struct. Anal. and Des., Univ. of Naples, P.le V. Tecchio, 80125 Napoli, Italy.
3. Assoc. Prof., Dept. of Civ. Engrg., Univ. of Salerno, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy.
4. Res. Asst., Dept. of Civ. Engrg., Univ. of Salerno, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy.