The modelling of infilled frames is generally very difficult because of the several parameters influencing their response. Specifically, the macro-models have many uncertainties related to the definition of the Equivalent Rod that simulates the panel. Main parameters involved in the definition of the Equivalent Strut Models (the width of the strut, the constitutive Force-Displacement law of the panel and the number of struts adopted to simulate the panel) induce a great variability of the structural global response. Consequently, the quantification of the uncertainties that influence the building safety verification becomes very important. In order to investigate this issue, three examples of buildings were developed and the characteristic points of the nonlinear law of the struts (yield and maximum strength) were changed within a range of allowable values. The objective is to appraise the sensitivity of the structural capacity (in terms of displacement) of infill models.