Recently, the design of building skins is achieving a strategic role, to meet more and more complex requirements, especially towards the goal of Nearly Zero Energy Buildings (NZEB).
In this context, Double-Skin Façades (DSF) offer great potentialities and are becoming increasingly popular among architects and engineers. On the other hand, in tall buildings, excessive displacements and accelerations can cause serious human discomfort issues. To mitigate this type of problems, Tuned Mass Dampers (TMD) can be considered as the default solution. However, the installation of TMD implies the sacrifice of valuable space near the top floor and the addition of large masses to the building. To overcome such shortcomings, the idea to let the DSF mass oscillate in order to mitigate the vibrations of the building has been proposed in the literature. Some Authors showed that DSF can successfully work as a distributed TMD without addition of new mass nor demission of useful building space. However, the use of DSF to reduce structural vibrations is hindered by the fact that the effectiveness of the damping is correlated with large displacements of the external layer. Further advancement of this idea, is thus subordinated to the realization of façades capable to effectively act as TMD while keeping displacements of façade within acceptable levels.
This project aims to develop a connection that could help to fill this gap. This will be realized by the design and the numerical and experimental validation of a device with two-stage behavior composed by a low stiffness element supplemented by a second-stage motion limiter. One or both of the components could be realized by means of Shape Memory Alloys or innovative nanostructured materials, such as carbon nanotube/polymer nanocomposites. This could add further value to the project by establishing a link between DSF, initially conceived only to improve the energy performances, with the concepts of kinetic façades and intelligent skins.
As discussed in previous Sections the use of Double Skin Façades as vibration devices is hindered by the fact that the effectiveness of the damping is correlated with large displacements of the external layer that cannot be tolerated both for constructive and comfort reasons. Further advancement of this idea, is necessarily subordinated to the need to realize connections between the façade and the structure capable to attenuate the vibrations of the structure while involving acceptable displacements of the external surface.
In this framework, the idea to use a two-stages device composed by a dissipative element integrated by a dissipative motion limiter to connect a movable Double Skin Façades to the main structure is new to the best knowledge of the components of the research group. This is a promising solution that could lead to the solution of the main issue related to the vibration performances of DSF.
Moreover, the idea to connect DSF to the structure by smart dampers based on Shape Memory Alloys or innovative nanocomposite materials is also new. This could add further value to the project as it may establish a link between DSF, initially conceived only to improve the energy performances of buildings, with the concepts of kinetic façades [1] and intelligent skins [2].
In summary, this project will investigate the feasibility of a concept that has not yet been discussed in the literature and that may lead to a link between different concepts at the interface between engineering and architecture.
As detailed in previous Sections, the research group has a well established expertise in the field of vibration damping devices, Shape Memory Alloys modeling, linear and nonlinear dynamics of non-smooth and piecewise defined systems. The synergy between the above mentioned skills offer the best conditions to produce an advance in the state of the art in the field of the use of DSF for the purpose of vibration mitigation in tall buildings.
[1] Moloney, J. (2011). Designing kinetics for architectural facades: state change. Taylor & Francis
[2] Wigginton, Michael, and Jude Harris. (2013), Intelligent skins. Routledge