Integrated Seismic Design of Structure and Control Systems

Passive structural control techniques are generally used as seismic rehabilitation and retrofit methodologies of existing structures. Most of the advanced research and applications of structural control in civil engineering has been focused on the analysis of existing structures integrated with passive, either hybrid or active, control devices in order to improve the structural performance under strong earthquakes. In all cases, both the structure and control system are therefore designed separately and only subsequently integrated by following the principles of a performance-based design. An example is the case of ‘‘Millennium Bridge’’ whose structural functionality has only been restored through the use of viscous dampers to reduce the resonance phenomena. An exciting consequence of structural control research is that it also opens the door to new possibilities in structural forms and configurations, such as slender buildings or bridges with longer spans without compromising the structural performance. This can only be achieved through the integrated design of structures with control elements as an integral part. In recent years, integrated optimal structural/control system design has been acknowledged as an advanced design methodology for space structures, however, not many studies and applications can be found in civil engineering. In this work, with specific reference to the supplemental passive energy dissipation through viscous or viscoelastic devices, the possibility of achieving seismic protection through the integration of elastic resources of a framed structural system as well as viscoelastic ones of a dissipative bracing system has been investigated. The innovative aspect, therefore, consists of considering the viscoelastic damping resources as design variables to control the dynamic response. A procedure for the integrated design of a framed structural system equipped with viscoelastic/viscous damper-brace component is therefore proposed and developed, in order to achieve an expected seismic design performance, by following the basic principles of the displacement-based seismic design and explicitly considering the dynamic behavior both of the structural system as well as the dissipative system. The choice of the optimal design is made by determining the combination of the design variables, which minimizes a cost index that is evaluated considering the relative cost between the elastic and viscoelastic dissipative resources. The structural optimization, developed in this work, made it possible to obtain new optimized solutions of the design problem for fixed shape and structural topologies through the integrated use of dissipative resources produced by dampers, resulting in slender structural systems with a high seismic performance. This methodology is, finally, a response to the futuristic idea to ensure an adequate seismic performance for structural solutions including innovative materials, charactrerized by a high slenderness