Wave loading on rock lighthouses

Abstract

Historical and contemporary observations of wave-impact loading on rock lighthouses during storms are presented.With climate change potentially causing sea level rise and more energetic wave climates, the longevity of these heritage structures cannot be taken for granted. To obtain a better understanding of the wave-structure interaction, Plymouth University has been working with the General Lighthouse Authorities to develop monitoring and modelling techniques suitable for these isolated masonry structures. Details of the field campaign, in which 2978 impact events were recorded during the winter storms of 2013/2014, are presented together with an initial analysis that begins to shed light on the dynamic response of these iconic structures. The results indicate that the response can be sensitive to the type of wave impact and that the overall motion of the Eddystone tower was less than might have been expected. A finite-element model of the tower was able to reproduce accurately the frequencies of the first and third modes of vibration but, unlike the field data, failed to show response at a frequency near the second mode. Preliminary attempts to apply wave loads estimated on the basis of ISO 21650 show reasonable agreement between the model displacements and those measured.

Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed

“…Significant infrastructural impacts included severing of a major railway line at Dawlish (UK), as well as damage to harbors, buildings, and coastal defense works. Out to sea, geophones on the Eddystone lighthouse registered ≈3,000 structure-shaking events during the winter (Raby et al, 2016).…”

Characterisation of Breaking Waves on the Eddystone Lighthouse: A Laboratory Investigation on Wave Pressure

“…Maximum run up, approximately 4 times the water depth h t , occurred for this breaker type. However, this value is lower with respect to the maximum run up observed in the 3D situation of the field during the UK winter storms of 2013/2014 (Raby et al 2015).…”

“…Geophones and cameras were installed on this structure, which is located on a perilous group of rocks some 21 km offshore from Plymouth. The field monitoring showed that the lighthouse can be exposed to different types of breaking waves (Raby et al 2015). Bagnold (1939) was one of the first to perceive that wave loading is affected by the amount of aeration involved during the breaking process.…”

Modelling the Eddystone Lighthouse response to wave loading

“…[1]; [2]; [3]; [4]) but limited observations of structural response have been provided in archive literature. The most notable accounts are by Robert Stevenson on Bell Rock lighthouse ( [4]; [5]) and as reported on a number of previous Eddystone lighthouses ( [1]; [5]). Whilst fascinating to read, at best they provide a patchy understanding of how wave impacts are related to tower motions.…”