1. Dept. of Structural Engineering, Milan Univ. of Technology (Politecnico), P.za L. da Vinci 32, 20133 Milan, Italy. E-mail: francesca.giussani@polimi.it
2. Professor of Theory and Design of R.C. and P.C. Structures, Dept. of Structural Engineering, Milan Univ. of Technology (Politecnico), P.za L. da Vinci 32, 20133 Milan, Italy. E-mail: mola@stru.polimi.it