1. Dept. of Mechanical Engineering, Polytechnic Univ. of Milan, 20156 Milan, Italy.
2. ECSD Engineering, Via Goldoni 22, 20129 Milan, Italy.
3. Dept. of Structural Engineering, Polytechnic Univ. of Milan, 20132 Milan, Italy.
4. CAD DataConsult, Via Cadolini 4, 20137 Milan, Italy.
5. Dept. of Industrial Engineering, Univ. of Parma, 43124 Parma, Italy (corresponding author).