Coupling energy refurbishment with structural strengthening in retrofit interventions

The reinforced concrete constructions built after World War II represent almost half of the European building stock. Such buildings are characterized by low energy efficiency, living discomfort and structural vulnerabilities especially in seismic prone areas, having been designed before the enforcement of modern building codes. A global integrated intervention for the sustainable restoration of the considered building stock is proposed in this paper. The conceived approach overcomes the shortcomings of the traditional renewal practice, targeting uncoupled solution of single deficiencies. The solution also stems as an enhancement of past pioneering techniques, such as the double skin, focusing on architectural restyling and energy efficiency upgrade. In the proposed approach energy efficiency and structural upgrading measures are coupled, and the exoskeleton is complemented with ad-hoc systems and devices to increase structural safety and seismic resilience. The intervention is carried out from the outside, with reduced impairment of the inhabitants and possible building downtime. Unlike traditional energy efficiency interventions, the structural upgrade entails a series of co-benefits: it allows lengthening the building service life, thus representing a viable and more sustainable alternative to the building demolition and reconstruction practice; it increases seismic resilience at district level, reduces life cycle costs and minimizes environmental impact over the building life cycle. Despite the research work be multidisciplinary, in this paper emphasis is made on the sole structural issues. The exoskeleton conceptual design is discussed and either over-resistant or dissipative solutions are proposed. Main principles of performance based design are presented, which allow minimizing the damage on the existing building. Finally, the case study of a typical residential building is presented, in which the possible use of the engineered double skin is proposed as an alternative to the basic double skin.