Vibration monitoring of all phases on Hjørundfjorden fjord crossing – measured differences between phases

Concerns regarding aeolian vibration on the Hjørundfjorden fjord crossing motivated a vibration monitoring campaign combined with a revision of the damping system. The 3.27 km span comprises four phases with nominally identical conductor and damping arrangements, while maintenance records indicate a higher occurrence of damper fatigue on phases exposed toward the open fjord. Accelerometers were installed on all phases in May 2025, enabling direct phase-to-phase comparison. The monitoring period coincided with ongoing damper replacement. The results show that vibration behaviour on very long fjord crossings can be phase-dependent even with similar damping layouts. While additional dampers reduced vibration activity on phase C, differences between other phases persisted despite identical…