Seismic enhancement of existing buildings by means of fiber reinforced concrete diaphragms

Floor diaphragms may provide an effective solution for reducing the seismic vulnerability of masonry buildings. Unfortunately, diaphragms are usually not present in historical building with wooden floors but often they are non present even in old R/C buildings where floors were made without shear reinforcement. A possible strengthening technique could be based on the application of a thin concrete plate reinforced with a welded mesh. In order to reduce the thickness of the plate, some suitable solutions may be obtained by using Fiber Reinforced Concrete (FRC) since the minimum concrete cover is no longer required because the reinforcement (fibers) is spread all over the concrete matrix. The adoption of FRC floor diaphragms is proposed and discussed in this paper; the early results from a preliminary numerical study are analyzed in order to asses the feasibility of this new strengthening technique and better organize an experimental program that is currently in progress.