1. Postdoctoral Researcher, Dept. of Mechanics and Civil Engineering, Univ. of Modena and Reggio Emilia, via Vignolese 905, 41100 Modena, Italy.
2. Professor of Structural Engineering, Dept. of Mechanics and Civil Engineering, Univ. of Modena and Reggio Emilia, via Vignolese 905, 41100 Modena, Italy (corresponding author).