Since the late 50's, in several studies the behaviour of infilled frame to horizontal actions was analyzed. The constant interest toward the topic is due to the high variability of the structural response to changes of mechanical properties of the masonry panels and modelling adopted in order to simulate the infill. Macro-modelling approaches, based on the equivalent strut model, give results dependent by variability of the assumptions adopted in the modelling, such as: the width of the connecting rod, the constitutive Force-Displacement law for cyclic actions and the number of struts adopted to simulate the panel. In addition, these simulations do not allow to investigate (in detail) the local effects caused by interaction between frame and panel along the contact surfaces.

Within the framework of the need to make use of a reliable methodology to simulate the infill panels, the present work proposes a research study on the calibration of the parameters characterizing the equivalent strut. The proposed approach, based on a rigid body spring model, allows with a numerical solver to obtain some initial assessments by varying of few geometrical and mechanical parameters significant.