Dynamic in situ tests for the calibration of an infilled R.C. Building F.E. model

Infill walls are commonly disregarded in the modelling of reinforced concrete (r.c.) frame structures and only their contribution in terms of mass is taken into account assuming that strength and stiffness do not affect the structural response. However, for strategic buildings, such as schools, hospitals, police and fire stations, it is crucial to preserve the infills from any damage, even for severe earthquake, in order to guarantee the building occupancy during the emergency management. Furthermore, these buildings are sometimes seismically protected with systems and devices (dampers, isolators, etc...) whose design requires the real dynamic behavior of the structure to be considered. To this purpose, it becomes crucial to accurately model the entire structure, including infill walls, and to validate this model on the basis of experimental evidences. In this paper a procedure to obtain accurate finite element (f.e.) models of infilled r.c. frame buildings is presented, referring to a real building case study. This procedure is based on the results of experimental and operational modal analysis of non-structural components and of the whole building, respectively. In particular, impact load tests with an instrumented hammer are performed on wall panels to identify the out-of-plane modal parameters (frequencies and mode shapes) and to estimate the mechanical properties of the masonry walls. Afterwards, the infill walls, with their estimated mechanical properties, are included in the f.e. structural model and the numerical global modal parameters are compared with the experimental ones achieved from in situ ambient vibration measurements and operational modal analyses of the global structure.