La Jument lighthouse: a real-scale laboratory for the study of giant waves and their loading on marine structures

Abstract

This paper presents results from an experiment designed to improve the understanding of the relationship between extreme breaking waves and their mechanical loading on heritage offshore lighthouses. The experiment, conducted at La Jument, an iconic French offshore lighthouse, featured several records of wave, current and structure accelerations acquired during severe storm conditions, with individual waves as high as 24 m. Data analysis focuses on a storm event marked by a strong peak in the horizontal accelerations measured inside La Jument. Thanks to stereo-video wave measurements synchronized to the acceleration record we were able to identify and describe the breaking wave responsible for this intense loading. Our observations suggest that this giant wave (19 m high) had a crest elevation high enough to directly hit the lighthouse tower, above the substructure. This paper reveals the potential for conducting ambitious field experiments from offshore lighthouses in order to collect valuable storm waves and wave loading observations. This offers a possible second service life for these heritage structures as in situ laboratories dedicated to the study of the coastal hydrodynamics and its interaction with marine structures. This article is part of the theme issue ‘Environmental loading of heritage structures’.

Deep neural networks for active wave breaking classification

“…Visual inspection of these results confirmed the ability of the neural network to correctly classify the naïvely identified wave breaking candidates and only keep instances that represented active wave breaking. Moreover, the same neural network was able to correctly classify active wave breaking events for the rogue waves seen at La Jument 29 and for the small wind-generated breakers seen in the Black Sea data. This result highlights the ability of the neural network to generalize well on the dataset, which is a difficult result to achieve.…”

Environmental loading of heritage structures

“…The field monitoring on La Jument determined natural frequencies and damping coefficients of the structure during a dramatic wave impact [4]. The stereo imaging technique that has been described in La Jument [3] is also being implemented on Wolf Rock lighthouse this summer, with expert advice from Alvise Benetazzo one of the paper co- More generic heritage coastal structures have been included in this special issue, as it features the historic Luarca breakwater in Spain [10]. Away from the coastal zone, and experiencing significant wind loading, two unusual heritage structures are investigated: masonry chimneys in Portugal [11] and steel transporter bridges in the UK [12].…”

“…Regarding the future of rock lighthouses: in the UK and Ireland, the General Lighthouse Authorities are committed to their use into the future, hence the funding of the STORMLAMP project. However, Filipot et al [3] hedge their bets and suggest that even if the La Jument lighthouse may be too expensive to keep as an aid to navigation in the future, it may serve as an outdoor laboratory to study extreme waves.…”

A Low-Cost Stereo Video System for Measuring Directional Wind Waves

“…More recently, Bergamasco et al [29] proposed WASS (Waves Acquisition Stereo System), the first open-source stereo processing pipeline for sea waves 3-D reconstruction. Its availability, combined with the low cost of the required setup, contributed to the flourishing of numerous works including [31][32][33][34]. Compared to conventional instruments, a stereo video system is considered a low-cost observation method, requiring a pair of synchronized video cameras connected to a computer.…”