Proceedings of the 18th World Conference on Earthquake Engineering - WCEE 2024

A large number of highly seismically vulnerable buildings includes several relevant and strategic buildings. Relevant buildings like schools, assembly halls, public offices, cultural institutions, and, in general, buildings with significant crowding, should retain their structural integrity since their collapse could cause major human losses and significant economic impact. Moreover, it would be appropriate for such buildings to remain fully operational even during seismic retrofit work. This has supported the development of seismic retrofit solutions based on rapid, low-impact, and reversible interventions that offer many advantages. First, they can be done while the building is operational. Second, they can be removed and rapidly replaced if damaged due to earthquake shaking. Third, they can be integrated to combine seismic resilience and energy efficiency, thus reducing the time and costs of two separate interventions. This situation has stimulated the use of external additive structures, commonly called exoskeletons, as a feasible solution based on a circular and sustainable economy. Typically, the research and applications deal with non-dissipative steel exoskeletons involving the application of diagonal grids (diagrids) or external steel concentric braces from the outside of existing RC buildings. This paper presents the design and assessment of dissipative exoskeletons based on steel slit dampers for the seismic retrofit of RC buildings. To this aim, a real case-study school building has been considered. The dissipative exoskeletons have been designed using a displacement-based design procedure that takes into account the secant stiffness and damping of the existing structure at the peak response. The geometry of the dumbbell-shaped steel strip dampers has been selected to avoid stress concentration, accumulation of plastic strain, and premature buckling failures and increase their energy dissipation capacity. The effectiveness of the retrofit strategy has been finally demonstrated by nonlinear time-history analyses under different sets of earthquake-strong ground motions.