Shear devices coupling exoskeleton and existing RC buildings for seismic improvement

Usually, the works for seismic improvement do not allow the use of the building. The interruption of use in many cases is not allowed especially for buildings with strategic or public service functions. In recent years, an alternative approach to intervention has spread that allows operating exclusively outside the structure through the use of a technology called a structural exoskeleton. The exoskeleton in many cases consists of a bi-dimensional or three-dimensional truss steel structure. The goal of this technology is to transfer most part the seismic action to the external structure. This allows for avoiding reinforcements to the existing structure. for the building-exoskeleton system to be effective against seismic action, the exoskeleton must be sufficiently stiff and the coupling device between the two structures must not produce internal constraints and generate unwanted stresses for the existing structural elements. A critical aspect of the application of this technology is the transfer of the floor seismic forces from the existing structure to the exoskeleton. The present work illustrates the study of an innovative building-exoskeleton coupling device to transfer the seismic shear forces of the floor from the existing structure to the exoskeleton without generating in-plane and out-of-plane bending interactions. The study of the coupling device was carried out as part of the seismic improvement project of a real case study. The seismic improvement project involves the construction of external shear walls consisting of steel trusses. The results of nonlinear numerical analyses on the global models of the building-exoskeleton systems as well as the results of local numerical analyses of the coupling device are illustrated.