DYNAMIC STIFFNESS ANALYSIS OF LAMINATED BEAMS USING A FIRST-ORDER SHEAR DEFORMATION-THEORY

In this paper the exact vibration frequencies of generally laminated b eams are found using a new method, including the effect of rotary iner tia and shear deformations. The effect of shear in laminated beams is more significant than in homogenous beams, due to the fact that the ra tio of extensional stiffness to the transverse shear stiffness is high . The exact dynamic stiffness matrix is derived, and then any set of b oundary conditions including elastic connections, and assembly of memb ers, can be solved as in the classical direct stiffness method for fra med structures. The natural frequencies of vibration of a structure ar e those values of frequency that cause the dynamic stiffness matrix to become singular, and one can find as many frequencies as needed from the same matrix. In the paper several examples are given, and compared with results from the literature.