**Author details**

Roberto Balia\* and Pier Paolo Manca Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università di Cagliari, Italy

\*Address all correspondence to: balia@unica.it

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
