Thin-walled structures are widely used for engineering applications where lightweight structures with high stiffness and high resistance are especially advantageous or even required. In this work, a novel analytical equation is developed to accurately predict the mechanical behavior of thin-walled beams. The Finite Element Method (FEM) was used to build the model and obtain the results. The newly developed equation is designed for calculating the displacement of a simply supported beam subjected to torsional loads, which are distributed at midspan using two triangular load functions applied in opposite directions in the FEM models. The Eureqa software was utilized to uncover hidden analytical models, which were subsequently validated. The goal is to provide a formula that allows for the comparison of analytical calculations with numerical results for combined bending and torsion loads. A FEM model of a hollow-box beam with a rectangular cross-section subjected to torsion was constructed, and analytical calculations were performed. The analytical results were compared with the numerical results to assess their accuracy, and good agreement was found. In the future, other models, such as internally reinforced beams, could be tested using this methodology. Additionally, different conditions could be applied to the model studied in this work to evaluate the limitations and validity of the developed analytical model.