Numerical analysis of a masonry panel reinforced with pultruded FRP frames

The paper presents a numerical study on the retrofit of a traditional masonry building with frames made by pultruded GFRP profiles, adjacent to the wall structure and connected to it with mechanical fasteners. This kind of retrofit solution – not yet explored in theory nor in practice – is similar to common steel frame retrofits, but it brings on the benefits of light weight and durability of the FRP composite material. This hypothesis of masonry retrofit, once proven effective and advantageous, would bring a considerable potential innovation among the available options. Three different frame geometries and two cases of masonry thickness were accounted for, to investigate the effectiveness of the retrofit GFRP frame on the wall’s in-plane static response to horizontal loads. The global as well as local (connection) failure behaviour of the wall-frame system was investigated with 3D finite element analyses; a general strength increase after the retrofit, up to about 130%, was found and a switch from rocking to diagonal tension failure mode was observed; the strength hierarchy of the retrofitted system was also analysed, to enlighten the retrofit’s effectiveness in granting residual strength to the masonry. The thinner masonry structure was clearly recognised to have got the greatest benefits, but the retrofit could also significantly improve the in-plane shear strength of the thicker wall. The wall-frame connection analyses pointed out that the bearing crisis is generally the failure mode. A comparison to steel structures of analogous capacity was also made in terms of weight and natural vibration frequencies, and supported the viability of composite FRP frames for retrofit.