**1. Introduction**

Steel-concrete composite bridges had a strong growth in railways and highways since the construction system provides an efficient and cost-effective form. The combination of steel and concrete in a single composite structural element enhances the individual advantages of both materials. By utilizing the tensile strength of steel in the main girder and the compressive strength of concrete in the slab, the bending resistance of the combined materials is greatly increased and larger spans are made possible. It allows overcoming difficulties caused by

© 2016 The Author(s). Licensee InTech. 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. © 2016 The Author(s). Licensee InTech. 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.

irregular orography and offers advantages in terms of resistance and ductility useful in high seismicity areas.

The chapter, precisely, concerns with a steel-concrete composite viaduct on a territory with a variable orography and focuses on the dissipation method of the seismic energy.

The context, which led to the choice of hydraulic devices with the stabilizer system, is analysed. Such devices, designed according to the stiffness of the substructures, allowed to limit and, partly, dissipate the stresses, induced by the earthquake, maintaining the underlying structures substantially elastic to the condition of LLS. Then, the checks have proven the capacity of the structures to support the stresses to limit state condition (LSC) without undergoing any damages, assuring curving capacity of the piers. The implementation of the devices has been preceded by the timely check of the functionality of the same and of the correspondence of the project-operating curve in accordance with the provisions of the pertaining European regulation, among which EN15129:2009 [1] as well as the Italian standard DM 14/01/2008 [2].
