STORMLAMP - STructural behaviour Of Rock Mounted Lighthouses At the Mercy of imPulsive waves

Lead Research Organisation: University College London
Department Name: Civil Environmental and Geomatic Eng

Abstract

Historic rock-mounted lighthouses play a vital role in the safe navigation around perilous reefs. However their longevity is threatened by the battering of waves which may be set to increase with climate change. Virtual navigational aids such as GPS are fallible, and reliance on them can be disastrous. Mariners will therefore continue to need the physical visual aids of these strategic structures. The loss of any reef lighthouse will be incalculable in terms of safety, trade and heritage.

Plymouth University has trialled the use of recording instruments to capture limited information on the loading and response of Eddystone Lighthouse, with the support of the General Lighthouse Authorities (GLAs) having legal responsibility to safeguard aids to marine navigation around the British Isles. The study evaluated the extreme logistical constraints of lighthouse operations and the feasibility of using instrumentation to understand the response of the lighthouse to wave loads, with results strongly encouraging a comprehensive study of the load and response environment.

Hence a full-scale project is proposed whereby field, laboratory and mathematical/computer modelling methods, novel both individually and collectively, will be used to assess six of the most vulnerable rock lighthouses in the UK and Ireland. Depending on the findings the investigation will then focus on extended full-scale evaluation of one lighthouse for the following two winters.

The field instrumentation run by University of Exeter, and which will include modal testing and long term instrumentation will require novel procedures and technologies to be created to deal with the challenging environmental and logistical constraints e.g. of access, timing power.

The modal test data will be used to guide the creation, by UCL, of sophisticated multi-scale numerical simulations of lighthouses that can be used with the data to diagnose observed performance in the long-term monitoring.

The numerical structural model will also be linked with advanced physical modelling at Plymouth University's COAST Laboratory, and numerical (computational fluid dynamic) simulations.

Finally, based on the structural and wave loading models, the long term monitoring will be used to characterize the wave loading in-situ at full scale.

Outcomes of the project will be used to inform the comprehensive structural health monitoring of other lighthouses both in the British Isles and further afield through the International Association of Lighthouse Authorities. This will lead to the identification of structural distress and reduction in the risk of failure through preventative measures. Methods developed will also be of relevance to other masonry structures under wave loads so the project team includes a number of industrial partners: AECOM, Atkins, HR Wallingford and the Environment Agency who have interests in this area. As the UK has a large number of ageing coastal defences whose vulnerability to wave load was demonstrated in the winter 2013/14 storms, the applicability of the STORMLAMP findings to these structures is an important additional benefit of the project.
 
Description Forced vibration using a 'shaker' enables identification of at least the fundamental modes of vibration.
Where there is a helideck, there are up to 4 'fundamental' modes, in two directions and with different phase with respect to the masonry structure.
Helidecks modify the modal mass, a key parameter controlling the response to external horizontal loads.
For Wolf Rock, the identified modal parameters provide a means to estimate the breaking wave modal impulses.
Monitoring data for the 2017/2018 winter storm season corroborate wave tank data on extreme loads.
Fastnet's extreme wave climate shows no statistically significant effects of due to the climate change.
Lighthouses are not affected by direct breaking wave loadings but by broken wave impacts - intensity is reduced but duration is increased, compared to unbroken wave.
Wave load does not vary linearly with breaking distance - depends on whether the wave can regenerate after it first breaks, so depends on precise bathymetry.
Impulsive force is always larger than the quasi-static force.
Force laboratory data can be effectively analysed by means of seismic analysis techniques such as deconvolution and Duhamel integral.
Structural response of lighthouses due to waves is governed by uplift and rocking. DEM and FEM with contact interfaces between discontinuous blocks successfully used for modelling extreme wave impacts.
Limit analysis used for assessing failure using Python code used on 6 lighthouses - size, shape, density, and height above the sea level were found to be crucial.
The vulnerability of the lighthouses, in combination with extreme wave hazard can be used for prioritising the detailed analysis and structural assessment.
Exploitation Route We will continue working on this for the next 18 months
Sectors Construction,Education,Environment,Culture, Heritage, Museums and Collections

URL https://stormlamp.org.uk/
 
Description Collaboration with AECOM for structural analysis of historic Lighthouses 
Organisation AECOM Technology Corporation
Country United States 
Sector Private 
PI Contribution Our structural analysis findings will be used from AECOM for future works of lighthouses.
Collaborator Contribution AECOM expressed concern about the long-term survivability of their historic rock lighthouses, built on surface-piercing reefs. AECOM provided drawings for structures build on certain lighthouses.
Impact Ongoing structural analysis of 6 lighthouses: Fastnet, Dubh Artach, Bishops Rock, Wolf Rock, Les Hanois, Longships
Start Year 2017
 
Description Collaboration with Irish Lights for accessing and studying the historic lighthouse of Fastnet. 
Organisation Commissioners of Irish Lights
Country Ireland 
Sector Private 
PI Contribution We are performing the structural analysis of the Fastnet Lighthouse for which the Irish Lights are responsible.
Collaborator Contribution The Irish Lights provide information (e.g archival drawing and photos) for the Fastnet Lighthouse and helicopter access to the remote structures
Impact Ongoing structural analysis of the Fastnet Lighthouse. Conference paper: Numerical modelling of Fastnet Lighthouse based on experimental dynamic identification, Proceedings of the International Conference on Advances in Construction Materials and Systems - ICACMS, Chennai, India (2017)
Start Year 2016
 
Description Collaboration with Plymouth University for the dynamic identification of lighthouses. 
Organisation University of Plymouth
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration with the Plymouth University for the structural analysis of historic lighthouses in the UK and Ireland. The structural analysis performed by UCL for the scope of the STORMLAMP project is based on the findings of the Plymouth University.
Collaborator Contribution The load of extreme waves on that can impact the studied lighthouses is identified by the Plymouth University
Impact Conference paper: Numerical modelling of Fastnet Lighthouse based on experimental dynamic identification, Proceedings of the International Conference on Advances in Construction Materials and Systems - ICACMS, Chennai, India (2017)
Start Year 2016
 
Description Collaboration with Trinity House for accessing and studying historic lighthouses in the UK 
Organisation Trinity House
Country United Kingdom 
Sector Private 
PI Contribution We are studying the structural condition and risks of lighthouses in the UK for which Trinity House is responsible.
Collaborator Contribution Trinity House provides information (e.g archival drawing and photos) for the investigated lighthouses and helicopter access to the structures.
Impact Ongoing structural analysis of 5 lighthouses: Dubh Artach, Wolf Rock, Bishop Rock, Les Hanois, Longships.
Start Year 2016
 
Description Collaboration with University of Exeter 
Organisation University of Exeter
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration with the University of Exeter for the experimental dynamic identification of historic lighthouses in the UK and Ireland. We are performing the structural analysis of the lighthouses based on the data provided by the University of Exeter
Collaborator Contribution On-site experimental test on lighthouses are carried out with the support of the University of Exeter. The initial data treatment is a responsibility of the University of Exeter . The structural analysis performed by UCL for the scope of the STORMLAMP project is based on the findings of the University of Exeter. The University of Exeter provides the equipment for the on-site dynamic identification and the data treatment.
Impact Conference paper: Numerical modelling of Fastnet Lighthouse based on experimental dynamic identification, Proceedings of the International Conference on Advances in Construction Materials and Systems - ICACMS, Chennai, India (2017)
Start Year 2016
 
Description STORMLAMP 
Organisation DES Enterprises UK
Country United Kingdom 
Sector Private 
PI Contribution laboratory visit
Collaborator Contribution research staff exchange 2 weeks
Impact drafting a joint paper
Start Year 2019
 
Description Oral presentation at the International Conference on Advances in Construction Materials 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The presentation attracted much attention because the topic was particularly new. I received plenty of questions from researchers and professionals about our findings and methodology. Moreover, researchers expressed their interest in examining potential collaborations between our groups of research.
Year(s) Of Engagement Activity 2017
URL http://www.rilem2017conference.org/