Factors Affecting Vibratory Stresses in Cables near the Point of Support

The wind-induced vibration of cables is the source of numerous fatigue failures in strands of electric transmissionline cables. At present, the emphasis in the field is directed at reducing or eliminating the amount of vibration by adding dampers and vibration absorbers rather than at reducing the induced stress in the cable by rational design of the suspension system. This paper is directed toward the evaluation of factors affecting the actual stresses or strains in a vibrating cable. The cable is considered to have both flexural rigidity and axial tension. Solutions for the bending stress have been derived for the dynamic case using the methods of standard beam theory. A static solution of the bending stresses is presented using the standard design criteria. The action of the suspension clamp, in the dynamic solution, is interpreted in terms of a factor ¿, which is introduced to represent how nearly the suspension clamp approaches the pinned suspension ¿ = 1, rather than a rigid suspension ¿ = 0. The pinned suspension would result in a point of zero reversed stress at the suspension clamp.