A novel semi-empirical approach to non-destructively evaluate the effect of infills on frame buildings

Masonry infilled frame (MIF) structures are commonly used as building system in many regions, and particularly in Latin American, Mediterranean, and Pacific countries, which are areas highly exposed to seismic events. It is well known that the influence of the infilled frames on the seismic response is affected by several sources of uncertainties which create unsafe unaccuracies in the seismic behaviour of a building. The use of existing complex models is an option which require a large number of specialized input values and data mostly obtained from in-situ destructive tests, thus making them infeasible in many practical cases. This research is a first attempt to provide an approach which provides prediction of the structural behaviour of a MIF with quantified uncertainty, and using as inputs values that can be obtained through a low-cost non-destructive test. The proposed method exploits the known interaction between the in-plane (IP) and out-of-plane (OoP) behaviour of the masonry wall by providing a semi-empirical model which predicts the IP stiffness of the MIF in terms of the measured OoP fundamental frequency. The semi-empirical approach has been nurtured with five experimental tests over one-fourth scale MIFs, where the OoP fundamental frequency variation has been obtained in terms of the IP deformation history. The results indicate that the proposed method can become a practical tool to experimentally quantify the contribution of the masonry infills of existing frame buildings, and also to theoretically predict it during design phase. However, a larger dataset of tests should be used on the calibration of the method before its application in real cases.