In this paper, the study of the inelastic seismic performance of a 5-storey reinforced concrete wall specimen, which was tested under bi-directional seismic excitations is presented. The structure has been sized and detailed following the French PS92 code, where the reinforcement is just designed so as to have the same strains at several levels. To investigate the simplifying assumptions made in design, and to assess the validity of the numerical tool, a 3-D refined non-linear analysis was conducted. Due to the outof-plane excitation, high variation of axial force results in smaller bending capacity. Since good correlation is obtained between calculated and test results, the numerical model is then used to predict the seismic response when only one-directional excitation is applied, or when vertical component is added to the other two horizontal components. In the presence of vertical excitation, additional variation of the axial force is to be expected.