1. PhD Student, Dept. of Constr. and Transp., Univ. of Padova, via Marzolo 9, Padova 35131, Italy. E-mail: valluzzi@caronte.dic.unipd.it
2. Civ. Engr., via Vespucci 92, Selvazzano (PD) 35030, Italy.
3. Full Prof., Dept. of Constr. and Transp., Univ. of Padova, via Marzolo 9, Padova 35131, Italy.