Different seismic behaviour of r.c. frame structures modelled with and without masonry infills

It is known that the seismic response of a structural system is highly influenced, in addition to the earthquake input, by the dynamic characteristics of the system itself. It has been observed during the L\u2019Aquila earthquake that some buildings have shown unexpected good performances. The aim of this paper is to understand why these structures, designed for accelerations lower than those recorded during the L\u2019Aquila\u2019s earthquake, have shown better performances than design ones. The attention is focused on a real case study of a reinforced concrete frame building structure located in L\u2019Aquila. The paper investigates the role of the masonry infills which, before reaching their ultimate capacity, allowed to avoid significant structural damage and excursion in the inelastic range