A sub-assembly based technique for calibration of numerical models of infilled r.c. frames according to experimental tests

Most existing buildings in the Mediterranean area suffer from structural deficiencies and need to be retrofitted. However, a proper selection of the seismic upgrading technique stems from a reliable assessment of seismic response based on accurate numerical models. Furthermore, it is widely accepted that the effect of infill panels should be considered to properly reproduce the seismic response of buildings with r.c. framed structure. Indeed, several studies have demonstrated that infill panels significantly increase the lateral stiffness of the frame and influence its dissipative capacity and collapse mechanism. Unfortunately, despite all buildings are endowed with infill panels, the contribution of these non-structural elements to the structural response has been often “conservatively” neglected, in favour of computational simplicity. In this framework, this paper presents a technique for calibration of the finite element numerical model of r.c. frames with infill panels based on the results of a quasi-static cyclic experimental test of a prototype infilled frame. The proposed technique is based on a sub-assembly approach and relies of the fact that (1) the response of the system is mainly governed by the infill panel for small amplitude displacements, while (2) it becomes coincident with that of the bare r.c. frame for large amplitude displacements. Hence, the mechanical properties of the bare frame and those of the infill panel could be separately extracted from the same cyclic response of the infilled frame. This technique has been here applied for the calibration of the numerical model of a one-bay one-storey r.c. frame with infill panel. A full-scale cyclic test of the infilled frame is also executed and the obtained structural response is assumed as target to be fitted.