Development of cable-exciting system for evaluating modal damping of stay cables

One of the effective alternatives to suppress hazardous vibration of stay cables is to use cable dampers. In order to design the cable damper optimally, it is necessary to exactly estimate the dynamic chatacteristics of existing cables. To estimate more reliable dynamic properties of stay cables, precise excitations inducing forced vibration are needed. Hence, in this paper, a cable-exciting system (cable exciter) controlled digitally is developed. A design formula for the cable exciter is also derived by the solution of the equation of motion of a cable-exciter system. The performance of the cable exciter is verified by sine sweeping tests and resonance tests for a cable model in a laboratory. Also from those tests, more reliable dynamic properties of the cable model are obtained. Thus, it is ascertained that modal damping of stay cables is proportional to the amplitude of cable vibration.