Existing RC bare frames reinforced with smooth rebars: Influence of the modelling approach

Several existing RC frame buildings were designed only for gravity loads and built with smooth rebars. Experimental results showed that the seismic behaviour of this kind of structures is different with respect to those built with deformed rebars; consequently, the classical modelling approaches are sometimes inadequate. The poor bond performance of smooth rebars provides high deformability to frame members that turns out to be an important resource for the seismic retrofit. In fact, the larger deformation capacity of the existing structure allows for more slender and flexible retrofit systems. A modelling approach to account for the smooth rebar slip contribution to the RC frame members overall deformability is presented and its results are compared to those of experimental tests available in the literature. Finally, an application to a bidimensional RC frame and its strengthening is discussed.