Free vibration analysis of thin-walled frames with use of node superelements

The paper deals with free vibration analysis of frames made of thin-walled members. The investigations are based upon assumptions of classical theory of thin-walled beams of non-deformable cross-section. The warping effects are included into the consideration. It should be observed that in the vicinity of the nodes the stresses and deformations are in inconsistency with these assumptions. To take into account these inconsistencies the stiffness and mass matrices of nodes necessary in the finite element method applied are determined with aid of the superelement concept. Some numerical examples related to the frame made of I-beams are presented. The frequencies and modes of free vibration determined by the method proposed are show and compared with results of the analysis carried out by the system NASTRAN and with aid of the classical frame model without the warping effect.