On lateral–torsional vibrations of elastic composite beams with interlayer slip

The lateral–torsional vibrations of composite beams are investigated in this paper, based on a variational approach. Composite beams studied in this paper are classified as composite beams with interlayer slip (composite beams with partial interaction or layered wood beams) or three-layer sandwich beams. It will be shown in this paper that both structural systems are governed by the same nature of differential equations. The theoretical framework of lateral–torsional vibrations of composite beams is given, and some engineering results are presented for the pinned–pinned strip composite beam. A simple closed-form solution is achieved for the lateral–torsional natural frequencies. The results are analogous to the ones obtained for the in-plane vibrations of composite beams (sandwich beam or composite beams with partial interaction) where the natural frequencies increase with the stiffness of the connection. Extension of these results to some more complex loading cases is envisaged, and a numerical procedure will be probably needed in the general case.