The unseen responses of remote offshore lighthouse in the face of severe storms are revealed in a new study by Plymouth University.
A team from the School of Marine Science and Engineering considered historical and contemporary observations of the wave impact loading on rock lighthouses during storm conditions.
They combined these with data obtained in a pilot study on the Eddystone Lighthouse during the winter of 2013/14, and found the motion of the tower was smaller than might have been suggested by anecdotal observations.
However, the waves still pose a threat with measurements showing they climbed up to 40 metres up the side of a structure not regarded among the most vulnerable lighthouses in the British Isles, let alone globally.
The study, published in the journal Maritime Engineering, was led by Dr Alison Raby, Associate Professor (Reader) in Coastal Engineering at Plymouth University.
She said: "There are about 20 masonry lighthouses around the UK that are exposed to wave action. Although mariners are making ever greater use of satellite-based navigation technologies, the General Lighthouse Authorities recognise the need to retain rock lighthouses as physical aids to navigation. However, there is concern about how well they would withstand the additional wave loading associated with predicted sea level rises and increased storminess."
To assess current impacts, Plymouth University technicians installed a range of measuring equipment on the Douglass tower, the fourth lighthouse sited on the Eddystone Reef (around 14 miles off the coast of Plymouth) and in situ since 1882.
These included remote-controlled video cameras to record the wave conditions around the structure, together with geophone systems to measure any structural response.
Lighthouse engineers working on two other structures off the South West coast - Wolf Rock and Bishop Rock - also provided reports of the visual and physical effects of the storm, much as engineers have done for centuries.
The equipment recorded 2,978 individual events between 20 December 2013 and 14 March 2014, with a maximum wind speed in excess of 100mph and waves spreading up the face at a maximum of 50 metres per second.
Vibration measurements from the geophones gave maximum velocities of 5.5mm/s and highest displacements of around 0.07mm.
A structural model of the tower, validated by these field data, has been used to assess its stability and confirms the tower is within the safe limits for the worst wave measured during these storms.
However, more work is needed to ensure the stability of other rock towers to even more dramatic wave impacts, and funds to extend this research have been sought.
Dr Raby adds: "People look at lighthouses and wonder how they can absorb such colossal wave impacts. It is possible the current Eddystone Lighthouse responds less than other lighthouses, but while the cylindrical base of the lighthouse may reduce the wave run-up, video data shows it does not prevent water from jetting up above 40 metres. In this case, designers have potentially learned from previous mistakes, but this is far from the most exposed rock lighthouse and the curious effect of the particular rocky outcrops will mean other lighthouse responses to wave impacts will be quite different."
The results of further tests using the COAST laboratory at Plymouth University and a computational study are currently being analysed, while more advanced equipment is being fitted to Eddystone and additional instruments are being deployed at the Longships Lighthouse off Land's End.
Dr Raby will also be presenting the research at the annual International Association of Lighthouse Authorities' Engineering meeting in Paris in April 2016.
Alan Williams | EurekAlert!
Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland
15.11.2018 | Faculty of Science - University of Copenhagen
The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences