ABSTRACT: Devices such as isolators, dampers and tuned mass dampers are now widely used in the construction industry for earthquake engineering to reduce vibration in new and, in a few cases, existing buildings. The application in to existing building is in general limited by the costs and in the case of historical building by local regulations. Aiming at the vibration control of existing structures in this paper it is proposed for the first time to exploit the structure-soil-structure mechanism as a vehicle to reduce the vibrations of structures due to seismic action. Specifically a novel device, herein called Vibrating Barrier (ViBa) hosted in the soil and detached from the structure is designed to protect a given structure. The ViBa is a massive structure whose structural parameters are calibrated to absorb portion of the ground motion input energy so to reduce the vibrations of the structure. Modelling the ground motion as zero-mean quasi-stationary response-spectrum-compatible Gaussian stochastic process, the soil as visco-elastic medium and linear behaving structures various examples are produced to show the effectiveness of the novel approach. Reduction up to 44% of the response has been achieved. KEY WORDS: Structure-Soil-Structure-Interaction, vibration control, Ground motion excitation, vibrating barrier. 1 INTRODUCTION The problem of reducing vibrations in structures, generally known as vibration control, arises in various branches of engineering: civil, aeronautical and mechanical. Unpredicted vibrations can lead to the deterioration or collapse of structures. In the field of earthquake engineering, modern strategies of seismic design aim to reduce structural vibrations by: i) increasing the dissipative properties of the structure; ii) moving the natural frequencies of the structure away from the frequencies in which the seismic action possess the highest energy; iii) modifying the energy transferred from the earthquake to the structure. The control of vibrations of structures is currently performed using passive, active or hybrid strategies. In the framework of passive control systems is it possible to categorize the following three general devices: i) tuned mass dampers, manufactured by adding one or more oscillators to the structure; ii) dampers able to transform the seismic energy in heat which is then diffused in the environment; iii) isolation systems, used mainly for earthquake applications, based on the idea of shift the fundamental frequency of the superstructure far from the main frequency of the earthquake. Apart from few attempts to protect existing structures the use of vibration control devices is still restricted to new buildings and/or constructions. One main reason is that the introduction of control devices in existing structures is too invasive, costly and requires the demolishing of some structural and/or non-structural components. This is clearly prohibitive for developing countries and for historical buildings. An alternative solution is to protect the structures introducing trenches or sheet-pile walls in the soil. However this approach seems to be more effective for surface waves coming from railways rather than seismic waves. There are, therefore, up-to-date no currently feasible solutions to protect cities from seismic ground vibrations. Bearing in mind the global necessity to protect existing structures from earthquakes and the limitation of current technologies a novel control strategy is proposed in this paper. The concept is based on the generally known structure-soil- structure interaction (SSSI) and on the findings in the pioneristic works of Warburton et al. [1] and Luco and Contesse [2]. The dynamic structure-soil-structure interaction among the structures occurs through the radiation energy emitted from a vibrating structure to the other structure. As a consequence, the dynamic response of one structure cannot be studied independently from the other one. Warburton et al. [1] studied the dynamic response of two rigid masses in an elastic subspace showing the influence of one mass respect to the other. Luco and Contesse [2] studied the dynamic interaction between two parallel infinite shear walls placed on rigid foundations and forced by vertically incident SH wave. They showed the interaction effects are especially important for a small shear wall located close to a larger structure. Kobori and Kusakabe [3] extended the structure-soil-structure interaction study to flexible structures and pointed out that the response of a structure might be sensibly smaller due the presence and interaction of another structure. A recent review of the structure-soil-structure interaction problem can be found in Menglin et al.[4]. An extension to the traditional structure- soil-structure interaction problem where only two structures are considered in the study is performed through the site-city interaction problem. Due to the difficulties involved in modelling the multiple interactions and the sustained progress in computational mechanics numerical approaches based on wave propagation and finite or boundary element analysis are usually adopted for the study of site city interaction [5-7]. Vibration Control of Structures through Structure-Soil-Structure-Interaction Pierfrancesco Cacciola 1 and Alessandro Tombari 1 1 School of Environment and Technology, University of Brighton, Cockcroft Building, Lewes Road, BN24GJ Brighton, UK email: p.cacciola@brighton.ac.uk, a.tombari@brighton.ac.uk Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 A. Cunha, E. Caetano, P. Ribeiro, G. Müller (eds.) ISSN: 2311-9020; ISBN: 978-972-752-165-4 559