Wind induced vibrations of suspension bridge hanger cables

This paper discusses wind induced vibrations observed for vertical locked-coil or parallel wire hanger cables of contemporary suspension bridges. It is demonstrated that these types of hanger cables are characterized by very low structural damping levels at all frequencies, being the fundamental prerequisite for the development of vibrations. Due to the nature of vortex shedding and the closely spaced natural frequencies of taut cables, vortex induced vibrations can be expected for the full range of wind speeds. Rain-wind induced vibrations of vertical hanger cables have been observed in the field as well as in wind tunnel tests. The strength of rain-wind excitation is considerably stronger than that due to vortex shedding yielding larger vibration amplitudes thus requiring more added damping for mitigation.