Performance of unpretensioned wind stabilizing cables in the construction of a cable-stayed bridge

A stabilizing cable (SC), used for mitigating buffeting vibration in a cantilevered structure of a cable-stayed bridge during construction, is normally installed with pretension. When a situation arises where only SCs are allowed in side spans, heavy counterweights in the center span are required to satisfy the force balance. The mitigating effect of unpretensioned cables was investigated using a wind tunnel in an attempt to eliminate the need for counterweights. An elastic wind tunnel test at a scale of 1/125 was prepared, and a series of comparative wind tunnel tests were performed. The vertical displacement at the cantilever tip of the center span and the horizontal displacement at the top of the pylon were measured, and stabilizing effects were then estimated. An unpretensioned cable produces a nonlinear motion because of a loss of tension. A quantitative evaluation of the stabilizing effect of an unpretensioned stabilizing situation indicated that the counterweight could be removed only when a moderate level of stabilization is required for a small- or medium-sized, cable-stayed bridge.