PROGRESSIVE COLLAPSE RETROFIT OF A STEEL-RC HOSPITAL BUILDING USING AN OUTRIGGER-BELT TRUSS SYSTEM

In recent years, there has been growing global concern regarding the potential for building structures to experience progressive collapse under abnormal loads. Numerous studies in the literature have focused on analyzing and designing methods to improve resistance against progressive collapse, and various technological retrofit solutions have been proposed. However, many of these studies rely on oversimplified models, limiting the applicability of their findings to practical scenarios. This paper introduces an alternative retrofit solution centered around an outrigger-belt truss system installed at the roof-top level of buildings. This system offers significant vertical stiffness and strength while requiring relatively small sections and minimal added mass. Additionally, it is characterized by its rapid, low-impact, and reversible implementation process, which allows the building to remain fully operational during the retrofitting process. This paper describes the progressive collapse analysis and retrofit of steel-reinforced concrete hospital buildings in Naples. A straightforward design procedure based on basic equilibrium principles is outlined. The effectiveness of this retrofit strategy is evaluated through non-linear static and dynamic analyses using real case studies, and its impact on existing structural members is discussed.