Lateral Vibration of Suspension Bridges

Abstract

Besides the pendulum action developed by the suspended deck, the restoring force exerted by a cable during lateral displacements is expressed by the horizontal component of the cable tension, times the curvature of the cable in the horizontal plane. Some authors consider an additional term linked to a pendulum effect of the cable itself, caused by the uplift movement which accompanies the lateral displacements. In the present note, the mathematical model is reviewed to show that, in the usual assumption of small amplitude vibrations, the presence of this second term is due to a sign error in the expression of the strain energy of the cable. Some evaluation of the first vibration modes period is reported.