Influence of the joint behaviour on the performance of orthogonal exoskeletons for seismic retrofit

The orthogonal exoskeletons can be used in seismic application to retrofit an existing building without interfere with the structure operativity. These types of structures are usually placed on the external perimeter of the existing structures and contribute to absorb the horizontal action in case of seismic events. The exoskeletons should be designed in function of the design target and depending on the lateral stiffness of the existing structures. Therefore, the exoskeletons lateral stiffness represents one of the key parameters in the design procedure; however, their structural stiffness is influenced by the joint features. In this work, the influence of the geometrical and mechanical characteristics of the joint on the global exoskeleton's performance is investigated. Non-linear numerical analyses were performed in order to investigate the performance of the exoskeletons accounting for the presence of the joints by the introduction of a no-dimensional local spring. The results show that the local response of the exoskeletons is affected by the joints features, and that in the design phase it is important to take into account the real exoskeletons lateral stiffness.