Most of the previous studies in the field of earthquake engineering have neglected the effects of vertical ground motion and are usually guided by horizontal motion. The EN1998 proposes action analysis of the vertical acceleration for certain types of elements and their length and their distance from the active fault. In this paper simply supported beams with various spans, 10, 15 and 20 m, are calculated for the action of real earthquakes with different intensities. Two typical cross sections were chosen: "T" cross section and rectangular cross section. The linear and nonlinear material models were used, and all the models were calculated using rigid and elastic supports. Through the combinations of these different spans, cross sections, material models and types of the supports, the influence and importance of the vertical component of the ground motion is estimated. Based on the results obtained it was concluded that there is a need for the application of vertical acceleration in the seismic analysis of these elements.