The influence of uncertainties of infill panels relative to the seismic response of RC existing buildings

Macro-modelling approaches are widely used for assessing the effects of infill panels. However, they contain some specific uncertainties concerning the definition of the equivalent strut (such as the width of the strut, the non-linear constitutive law under cyclic actions and assignment of mechanical properties in multiple strut models) that causes the variability of global structural response. As a result, there is the need to identify what are the parameters that influence the overall response of the building. After the identification of significant parameters, it is crucial to quantify the variation of the results regarding the safety verification of the building. In order to investigate this aspect, for two existing buildings with different heights, using a range of permissible values, the characteristic points (yield strength and maximum point) of the cyclic non-linear law were changed. The procedure has been carried out with the other preliminarily fixed parameters of the equivalent struts. With this approach, a variation of the safety in performance terms was assessed by carrying out a sensitivity analysis of the non-linear cyclic law. The results proposed lay the foundations for further consideration of issues relating to the modelling uncertainties and the development of simplified models for the assessment of existing structures designed to withstand only vertical loads. Keywords: infilled frames, existing buildings, non linear static analysis, earthquakes, dynamic loading, seismic assessment.