The aim of this paper is to present the influence of the subgrade reaction coefficient modelling on the simple 3D frame. For simplicity, it was assumed that the construction was made on the square foundations on granular soil. The soil reaction coefficient is modelled by different expressions drawn by different authors. For this reason different values of the coefficient were obtained. In order to observe the behaviour of these coefficients for each author curve families are created. They give us the relationship between the dimension of the square foundations and the value of the reaction coefficient. The paper then follows the response of the characteristic structural framework to these impacts.