A numerical study on the seismic behaviour of unreinforced masonry buildings with flexible diaphragms

The paper presents a comparison between different methods of analysis and different numerical models to investigate the seismic behaviour of unreinforced masonry buildings with flexible diaphragms. The comparison is performed analysing a two stories prototype tested on shaking table at the CNR-ENEA research centre of Casaccia (Italy). The first numerical model has been built by using the finite element (FE) technique, while the second one has been built by a simplified macro-element (ME) approach. Both models were employed to perform nonlinear static and time-history analyses. The shaking table tests were simulated to analyse the behaviour of the prototype from the initial elastic state until the development of extensive damage. Main results of all analyses are critically compared and discussed in order to investigate the effectiveness of both simplified models and analysis methodologies. Eventually, numerical results are compared with available experimental data. The FE model is able to predict with reasonable accuracy the damaged areas and the incipient collapse mechanism, as well as the collapse load. The ME model is able to predict the collapse load however, a satisfactory reconstruction of the actual collapse mechanism has not been obtained due to the limits of the approach. Nevertheless, the simplified model is able to predict accurately the accelerations at the top floor measured in the tests.