Disproportionate collapse resistance of buildings during retrofitting

In recent years, research on progressive collapse and robustness of structures has significantly increased. According to national and international building codes, the structure should be able to avoid partial or total collapse under extreme events, such as fire, explosions, impact or consequences of human error. The latter class of accidental events includes wrong operations during construction or retrofitting, which often cause the collapse of both historical and modern constructions. A few studies have evaluated the progressive collapse resistance during structural retrofitting. This paper presents the main findings of a numerical investigation that was aimed at quantifying the residual loadbearing capacity of a real reinforced concrete (RC) building that actually suffered a partial collapse during structural retrofitting works. Alternative modelling options are discussed in terms of computational efficiency to provide practice-oriented recommendations for robustness assessment of buildings that are scheduled for structural retrofitting.