Measurement and modelling of torsional warping free vibrations of beams with rectangular hollow cross-sections

This contribution contains the results of experimental measurements and modelling of torsional warping free vibrations of beams with rectangular hollow cross-sections. The experimental results are compared with results from a semi-analytical method, proposed by the authors, and from Finite Element (FE) computations by means of a standard commercial code. In these calculations, beam, solid, and shell elements are used. The semi-analytical calculations are based on the analogy between second-order beam theory, including consideration of the shear force deformation effect, and non-uniform torsion, considering the Secondary Torsion Moment Deformation Effect (STMDE). The influence of warping and of the STMDE on the torsional eigenfrequencies and eigenforms is evaluated. The difference between the measured and calculated eigenfrequencies is investigated and quantified.