In building production industry, infill walls which are brittle elements are generally used. Nowadays, researches for alternatives to these brittle structural elements are still ongoing. In this study, low density two different polyurethane wall block (Polyurethane wall block and interlacing polyurethane wall block) are used as infill wall. In the experimental part of the study, single spanned, one frame and two infill wall frame system are prepared. Lateral loading tests of the frame systems have been performed in the laboratory. Macro and simplified micro models of the frame system has been prepared using finite element modelling (FEM) as the numerical part of the study. Incremental pushover analysis is performed for the created finite element models. From the FEM analysis results; capacities of load-displacement, stress, separation, ductility, energy dissi-pation and local buckling conditions of the frame systems are evaluated comparatively. It is seen that the finite element analysis results and the test results are compatible. The polyurethane wall added to the steel frame system increased the base shear force, system rigidity and energy dissipation capacity by approximately 64-68%, 25-40% and 50-62%, respectively. In addition, a macro model proposal is presented to simplify the modelling of the polyurethane wall block in the computer environment.