Comparative analysis on the seismic behaviour of unreinforced masonry buildings with flexible diaphragms

The paper reports a comparison among different methods of analysis and different numerical models to estimate the seismic behaviour of unreinforced masonry buildings with flexible diaphragms through the investigation of a reference masonry prototype. The prototype was a two-storey building tested on shaking table at the CNR-ENEA research centre of Casaccia (Roma, Italy) under increasing natural ground motions in order to analyse its seismic response from initial elastic conditions until moderate to extensive damage. A first numerical model was built with the finite element technique, and was employed to perform nonlinear static analyses (pushover). A second one was built based on the simplified macro-element approach and, being less computation demanding, was adopted to perform nonlinear dynamic analyses. The 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 the available experimental data. The FE model is able to predict the damaged areas and the incipient collapse mechanism, as well as the collapse load. The macro-element model is able to predict the collapse load but, due to some limitations of the approach, a satisfactory reconstruction of the actual collapse mechanism was not obtained. Nevertheless, the simplified model is able to fairly accurately estimate the accelerations at the top floor measured in the tests.