Risk and reliability based approaches for seismic retrofitting by means of dissipative exoskeletons

Nowadays, the main trends in earthquake engineering show growing interest in probabilistic approaches to seismic design, particularly focusing on two principal topics: seismic Risk evaluation and structural Reliability. Seismic Risk is a probabilistic measure that makes it possible to quantify any type of loss due to seismic events that may occur in constructions at a given site, within a specified time interval. Structural Reliability, on the other hand, can be defined as the probabilistic measure of the ability of a structure, or one of its structural elements, to meet specified performance requirements. Therefore, one of the main challenges is to consider well-established retrofitting techniques, such as seismic isolation or elastic and dissipative exoskeletons, within methodologies based on seismic Risk and structural Reliability. This work addresses one of these challenges, specifically focusing on dissipative exoskeletons. Starting from two previously proposed procedures, developed within both Reliability based and seismic Risk based approaches, the work proposes an improvement, enabling designers to explicitly account for dissipation in exoskeletons. It is shown how this allows selecting the optimal characteristics of dissipative exoskeletons in order to reduce seismic Risk or ensure a given level of Reliability.