Internal resonance in a kinematically excited system of rods

In this paper the method of analysis of internal resonance in the system of rods under vertical kinematic excitation is presented. The elements of the system are connected with articulated joints. The couplings of elements of the system through internal longitudinal forces, which are the parametrical ones are taken into account. The equations of motion are obtained from the Lagrange's equations and the harmonic balance method is applied. The small nonlinear forces connected with damping are necessary to get the stable amplitudes of vibrations. The considered problems may have the practical significance for the paraseismic phenomena when the weak excitation may couse the big effects because of the autoparametric resonances.