1. Department of Structure for Engineering and Architecture, University of Naples ‘Federico II’, Naples 80125, Italy;
2. Department of Civil and Environmental Engineering, University of California Berkeley, Berkeley, CA 94720 e-mail:
3. Professor Mem. ASME Department of Civil and Environmental Engineering, University of California Berkeley, Berkeley, CA 94720 e-mail:
4. Professor Faculty of Mathematics, University of Duisburg-Essen, Essen 45117, Germany e-mail: