Steel exoskeletons for integrated seismic/energy retrofit of existing buildings - General framework and case study

The implementation of strategies for the decarbonization of the existing buildings by 2050 and the reduction of polluting emissions is urgent, for energy, economic and environmental reasons. Moreover, the built heritage undergoes structural deterioration for which restoration interventions are required. Seismic and energy improvement strategies are usually treated separately. Conversely, this paper proposes a holistic approach to improve both structural and energy efficiency of existing buildings. The innovative aspect is to obtain a dual objective by exploiting a single element, i.e., the exoskeleton. This component is an external self-supporting structural system connected to the existing building structure for improving strength, stiffness, and/or dissipation capacity under seismic actions. Contemporarily, it defines a new building envelope with different functions, such as ventilated wall, solar greenhouse, shields, and support for insulating panels or solar panels. This approach is applied to a case study, a reinforced concrete building in central Italy. The exoskeleton is rigidly connected to the existing building and designed to absorb the seismic loads and prevent damage to the structure under seismic excitation. The exoskeleton is also used for energy retrofit, by combining active and passive solutions. A design procedure is illustrated step-by-step for the case study. The results show a significant improvement of thermal characteristics of the building envelope, with a relevant reduction of primary energy, and of the seismic capacity of the existing structure that preserves its elastic behaviour. Moreover, this approach is also convenient from an economic point of view compared to a total demolition and reconstruction.