In steel-concrete composite structures, the behavior of the shear connections is of great importance. This behavior is generally characterized by the load-slip curve obtained from experimental push-out tests, however these tests are expensive and time-consuming. In this study, a numerical model is developed to represent the behavior of a push-out test. The theoretical model considers the non linear behavior of steel and concrete of the modeled specimens. The model is validated on the basis of experimental results from four push-out tests with samples using headed studs. The real behavior of the studs was simulated by a three-dimensional quarter-scale finite element model using the software ATENA. The finite element calculation can represent the real behavior of the push-out test. Then, the model has been used for further parametric analysis with flange thickness and different spacing of the studs.