Change in the Torsional Stiffness of Rectangular Profiles under Bending Stress

This article presents the results of research on the change in torsional stiffness of two rectangular profiles, arranged one on top of the other, which were permanently connected at their ends. The flat bars were expanded in the middle of their active length. The test involved determining the increase in the stiffness of a twisted test set before and after expanding. The authors present an analysis of the structure load and compare the results of tests carried out using analytical (for selected cases), numerical and experimental methods, obtaining satisfactory compliance. The analytical calculations included the influence of limited deplanation in the areas of the profile’s restraint. The ANSYS package software was used for calculations with the Finite Element Method. A change in the stiffness increase index at torsion was determined. The obtained results showed that expanding the test sets in their middle causes an increase in torsional stiffness, which is strongly dependent on the design parameters such as bending deflection, torsion angle and dimensions of the cross-section of the flat bar in the package.