Following a successful modal test at Les Hanois lighthouse, off the coast of Guernsey, the Vibration Engineering Section embarked on a data gathering exercise at Wolf Rock lighthouse 15km southwest of Land’s End, Cornwall. This was the second in a planned sequence of modal tests of offshore rock mounted lighthouses around the British Isles, as part of the EPSRC-funded project STORMLAMP (STructural behaviour Of Rock Mounted Lighthouses At the Mercy of imPulsive waves).
After fears that the testing would be delayed, due to a dense blanket of fog over the sea at Sennen Cove, the team for Wolf Rock, comprising James Bassitt (photo 5), VES Experimental Officer, Research Fellow Emma Hudson (photo 7), Laboratory Technician Ian Moon (photo 4) and Alessandro Antonini, Research Fellow in the School of Marine Science and Engineering at the University of Plymouth (photo 8) set off for the lighthouse from St Just Airport by helicopter.
Due to the bulk of the 350kg equipment, including a horizontal shaker, amplifiers, laptops, cabling, cameras and accelerometers, it took two helicopter journeys, courtesy of Trinity House, to transport the Wolf Rock team to the lighthouse where, on arrival, they decanted the equipment into the service room at the top of the lighthouse and installed the computers in the battery room, lowering equipment throughout the levels by rope.
As well as carrying out modal tests in real time, the team installed accelerometers throughout the levels of the lighthouse, to capture data and measure the response of the structure during stormy weather.
Despite high winds coming off the land across the sea, the modal tests were successful, and the team left the lighthouse after seven and a half hours.
James Bassitt, who managed the data acquisition and on-site modal analysis, said: “The whole exercise was logistically harder than at Les Hanois, because the lighthouse was narrower, taller and access to the helideck was restricted.
“It was difficult to carry out the modal testing, because the background noise from the wind was far outweighing the forces we were generating. But we persevered and completed the testing successfully.”
The next data gathering exercise will take place at Longships Lighthouse, off the coast of Lands End, in August 2016.