In reinforced concrete buildings, non-structural elements (NSE), such as masonry infills and parapets, constitute the cause of a considerable number of fatalities and huge economic losses in developed countries, in the case of medium magnitude earthquakes (4-6 Mw). As an example, during the 5.2Mw 2011 Lorca (Spain) earthquake, falling debris from unreinforced masonry NSE gave rise to the nine fatalities incurred. The majority of these elements were located in 4 to 6-storey reinforced concrete residential buildings.

Within this framework, this contribution addresses the characterization of the seismic demand of NSE through the study of the response of a building in Lorca pertaining to the described structural type, by means of the Floor Response Spectra (FRS) method. For this purpose, the infilled frame model was created in SAP2000 with masonry infills simulated by equivalent struts. The infilled frame model is calibrated so as to fit with the main elastic period of the building, identified by means of ambient vibration tests conducted with a Tromino device.

The FRS results obtained with the numerical model by a Linear Time-History (THA) analysis simulating the Lorca earthquake, are compared with the results suggested by the Eurocode in force and by the Italian Building Code. Specifically, in the case of the Italian Building Code, both the simplified formulation for moment resisting frame buildings and the modal superposition spectrum-to-spectrum approaches are considered. Finally, the potential resonance of the dynamic behaviour between the obtained FRS and the natural periods of the masonry parapets located at the top of the building is discussed.