Often, the lower normal modes of slim but complicated structures can be computed with sufficient accuracy if the computations are based upon a tapered continuous beam in which the stiffness and inertia of the beam match those of the structure at a large number of points along its length. Shear motions play a dominant role in these calculations. Even with the continuous beam approximation, the numerical computations involved are lengthy and time consuming. An equivalent electric circuit for the beam makes it possible to substitute model experiments for lengthy calculations. It is here shown that such an equivalent circuit can be constructed which is made up of lumped passive components. Given such a circuit, it is then possible to determine experimentally the gross responses of the structure to an arbitrary excitation.