Earthquake and wave impacts recorded on Wolf Rock Lighthouse as part of EPSRC STORMLAMP project

A single JA-70SA triaxial servo accelerometer was installed in Wolf Rock’s battery room (level 7) on 7th September 2017, with a NI cRIO data acquisition recording data via a NI USB-9234 four-channel digital to an analog converter. Communication using 3/4G mobile communication and a high gain antennae was initially established briefly but communications were lost soon after. During a subsequent visit on 6th February 2018 by James Bassitt (University of Exeter) and Alison Raby (University of Plymouth) as part of the Trinity House maintenance schedule, the USB data storage device was retrieved and communications re-established.

During the period 9/7/2017 to 6/2/2018 the United Kingdom experienced a number of severe storms including Storms Aileen (12-13/9/2017), Ophelia (formerly Hurricane Ophelia, 15-18/10/2017), Brian (20-22/10/2017) and Eleanor (2-3/1/2018).

The strongest wave impacts were experienced during Storm Brian; the figure shows the accelerations caused by a particularly strong impact at around 5:00 AM, along with its frequency content. The lighthouse comprises over 3,000 t of granite blocks and over 11 t of steel and aluminium helideck, and the measurement fits lighthouse keeper anecdotal evidence of the lighthouse rocking during severe storms.

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Horizontal acceleration response caused by Storm Brian, October 2017SL4

A rather gentler rocking would have been experienced by anyone on the station on 17th February at the time of the 4.4 magnitude Welsh earthquake. The plots show the horizontal vibrations, 100 times smaller than the strong wave impacts of the major storms. The earthquake signal was recorded during low tide and without significant wave impacts, even on a windy day.

Horizontal response caused by Welsh earthquake, February 2017



Latest funded PHD studentship opportunities from the Vibration Engineering Section (VES)

To find out more about our latest funded PHD studentship opportunities (deadline 10th January 2018), please see below:

Identification of Human-Structure Interaction for Footbridges Using Motion Capture Technology -Engineering – EPSRC DTP funded PhD Studentship Ref: 2946

Future Drone for Visual Inspection of Civil Infrastructures – Engineering – EPSRC DTP funded PhD Studentship Ref: 2920

Big Data Analytics for Monitoring-Based Management of Long-Span Bridges – Engineering/Computer Science – EPSRC DTP funded PhD Studentship Ref: 2912





Modal test of Eddystone Lighthouse

As part of EPSRC-funded project STORMLAMP (STructural behaviour Of Rock Mounted Lighthouses At the Mercy of imPulsive waves), the Vibration Engineering Section carried out a modal test of the Eddystone Lighthouse southwest of Plymouth from 10th to 11th October 2017. This was the final test in an experimental campaign that has also included lighthouses at Les Hanois (Guensey), Wolf Rock, Longships and Bishop Rock (west of Land’s End, Cornwall), Fastnet (southwest Ireland) and Dubh Artach (west of Oban, Scotland).

The Vibration Engineering Section (VES team) of James Brownjohn, Alessandro Antonini and Wai Kei Ao (Vincent) were joined by Plymouth University’s Trevor Bevan. The team flew from Castle Air in Liskeard (photo: Castle Air), with the test equipment following in a second freight-only flight.

Castle air
Castle Air

Eddystone Lighthouse is 49m tall, and has 12 levels. The entrance level is only used in emergency as it is accessed by stair rungs up the almost vertical face of the lighthouse. The engine room is directly above this, housing the generator that powers services when the lighthouse is temporarily manned for maintenance, followed by the oil room to store the diesel. Next the WC/shower room,’ water tank’ room making a comfortable spare bedroom, then the day room (kitchen). Above this is the sub-light room for electrical services, the bedroom (photo: Bedroom) and the battery room (photo: Battery room) where the data acquisition equipment was setup. At the top of the masonry structure is the lantern room where the shaker was located (photo: Shaker) and where the light is located (video: Lantern).

Battery room
Battery room
Shaker KM

The steel helideck structure is bolted to the crown of the masonry structure. A gallery level halfway up the helideck is used for loading and unloading equipment and personnel, and provides a good viewpoint, particularly of the arriving and departing helicopter flights (video: EC135 departure). For example compare the calm conditions on arrival (photo: Tower base) with the more lively conditions before departure on day two (photo: Smeaton stump). The stump of the Smeaton tower (relocated to Plymouth Hoe) is visible in (photo: Tower base), and almost all the time a seagull is sitting on top of the central pole. The solar panels around lantern level power the lighthouse when the generator is not running.

Tower base
Tower base
Smeaton stump

The team spent some time investigating the helideck platform itself. The dodecagonal platform (photo: Arrival) surrounded by spars and safety netting, is supported over the lantern by a ring of bolted and welded structural steelwork. An array of four horizontal accelerometers was set (photo: Helideck accelerometer) to characterise the in-plane rigid body behaviour, while heel-drops (photo: Helideck heeldrop) were used to check the out-of-plane natural frequency, showing the helideck behaves like a high frequency floor. The extensive information about the helideck should permit detailed study by finite element analysis.

Arrival. Photo by Trevor Bevan
Helideck acceleromter
Helideck accelerometer
Helideck heeldrop
Helideck heeldrop

The second afternoon departure was brought forward due to deteriorating weather but for the first time in the campaign allowed plenty of time to for the measurements, including single measurement of the whole structure overnight. A very clear set of vibration modes was identified by both ambient and forced vibration testing, confirming the 4.4 Hz first horizontal (cantilever) mode of the lighthouse observed in previous single-point monitoring.

To find out more about the Vibration Engineering Section, visit our website.


Structural Testing of a Heritage Railway Bridge

On Thursday 1st June, a team of researchers from the University of Exeter travelled to Watchet to perform testing on the Mineral Line Bridge. The bridge forms part of the West Somerset Railway, a heritage railway line with 20 miles of track in South West England. The team included Farhad Huseynov, Yan Xu, Jalil Kwad, Karen Faulkner and Linus Tonui.

Photo A
Locomotive passes over the Mineral Line Bridge

The Mineral Line Bridge is located on the outskirts of Watchet and was originally constructed to carry the Minehead route over the West Somerset Mineral Railway. The Mineral Railway now operates as a footpath and cycle path open to the public. The bridge opened in 1962, has a single span of 14 m and is constructed skewed to the pathway beneath.

The aim of the testing was to measure the structural deformations of the bridge under loading from passing trains, a combination of steam and diesel engines. A series of strain sensors, inclinometers and LVDT sensors were installed on the bridge. A number of targets were also installed on the bridge to measure deflections using an Imetrum camera.

Photo B
Jalil Kwad installs the strain sensors on the bridge

The strain sensors were installed below deck at mid-span, with the inclinometers installed above deck at each support, and quarter-span. Data was recorded during each passing train.

Photo C
Imetrum cameras and targets installed on the bridge

The Imetrum camera was used to measure deflections of the bridge under loading from the passing trains. Three Imetrum cameras were set up on tripods and targets were installed, one at mid-span on the bridge deck and two on the western abutment, previously identified as an area of interest.

Photo D
The team in action, Yan Xu (front), Farhad Huseynov, Linus Tonui and Jalil Kwad (left to right)

The weather conditions were favourable, sunny with low winds. This led to limited interference from the environmental conditions, allowing for a clearer understanding of the train loading on the bridge.

Photo E
Raveningham Hall locomotive passes over the bridge

To find out more about the Vibration Engineering Section, visit our website.



Dubh Artach Lighthouse modal test

Dubh Artach Lighthouse, Southwest of Mull on the Scottish West Coast was designed by Thomas Stevenson (father to the author Robert Louis), first ‘exhibited’ in 1872 and fully automated in 1971.

As part of the EPSRC STORMLAMP project, a team visited the lighthouse on 8th and 9th May 2017 to carry out a modal test. Alessandro Antonini took the modal test equipment by van from Plymouth University while James Bassitt and Karen Faulkner from the University of Exeter’s Vibration Engineering Section travelled via Glasgow Airport.

Dubh Artach helipad is just above sea level, so, as well as usual weather restrictions, helicopters (flying from the Trinity House depot in Oban) can only visit at low tide. Luckily, the weather was excellent, with zero cloud cover, perfect visibility and minimal wind.

Karen Faulkner watches helicopter lift off from Dubh Artach Helipad.

Access to the lighthouse is via vertical steps and all equipment, including a 50 kg shaker, had to be hoisted to lantern level using a temporary crane.

Access to lighthouse via steps, equipment hoisted by crane.

The signal to noise ratio for forced vibration testing was perfect, providing extremely clear resolution of vibration modes, with the shaker mounted on the lantern level walkway, just visible in the photograph.

Drone view of lighthouse with shaker at 6 o’clock position on lantern walkway.

Conditions were also perfect for flying the survey drone, providing some stunning views:

After staying overnight on the lighthouse, the team returned to Oban, then to Exeter and Plymouth.

To find out more about the Vibration Engineering Section, visit our website.


Modal test of Jiangyin Suspension Bridge

As part of the EPSRC-funded BAYOMALAW project, a team of researchers from Exeter and Liverpool travelled to Jiangyin in Jiangsu province, China to carry out a modal test of the Jiangyin Suspension Bridge.

south_tower_view resized

Jiangyin Bridge has a single suspended span of 1,385m, with straight back stays. The concrete towers rise 191m above ground level and each have three hollow portal beams. The mid portal is illustrated by the bridge name in stylised Chinese characters, created by (and signed by) the former Chinese premier Jiang Zemin, who opened the bridge in 1999. At the time, the bridge was the world’s fourth longest span and the furthest downstream on the Yangtze River.

The 32.5m wide 3m deep steel box deck carries three traffic lanes (plus a narrow emergency lane) in each direction. There are 2.2m wide cantilevered walkways either side, although these are for maintenance as there is no pedestrian access to the bridge. These walkways were used by the test team for moving the loggers around.

Test team (left to right): Yu, Zhen from Jiangsu Transportation Institute (JSTI), James Brownjohn and Karen Faulkner from Exeter,  Yichen ZHU from University of Liverpool and James Bassitt from Exeter

The exercise was primarily an extreme test of the capabilities of two new technologies.

First, a new synchronised wireless logging system was created by James Bassitt (hardware) Vincent Ao and Emma Hudson (software). Four loggers were taken to China (as checked baggage) with a set of 12 force balance accelerometers and a set of short signal cables.  These loggers are synchronised to a fraction of a microsecond before a measurement then distributed over the bridge deck and towers in a sequence of measurements to record ambient vibration signals.

James Bassitt and Karen Faulkner synchronising the loggers at the start of a day of measurements.

Some 14 separate measurements were made over a period of three days (25th-27th April 2017). For each measurement, the master logger was left recording vertical and lateral vibrations continuously at hanger locations H67 and H71 on the east walkway (there are 85 pairs of hangers each side) while other (slave) loggers were ‘roved’ to record for at least an hour synchronously at other locations on the east and west sides and inside the south tower.

James Bassitt and Karen Faulkner move slave logger to a new measurement location.

The weather conditions were mostly benign; cloudy, cold, hazy and breezy on the first two days, clearing to a fine sunny day for the tower measurements. Due to pollution and unpleasant atmospheric conditions resulting from the heavily industrialised area around Jiangyin, team members wore protective face masks most of the time.

The second major technology being evaluated was the operational modal analysis planning and evaluation procedure developed by Professor Ivan Au as part of the BAYOMALAW collaboration with the University of Liverpool.

BAYOMALAW stands for ‘Bayesian operational modal analysis law’, and the main aim of the project is to establish uncertainty laws for modal testing to optimise tests such as these. BAYOMALAW aims to establish the best measurement configurations and the resulting uncertainties in modal parameters in terms of natural frequencies, damping ratios and mode shapes. Jiangyin is an extreme test because of its ultra-low natural frequencies and its weak lateral response buried in quasi-static effects of deck rotation.

As part of the procedure, a ‘huddle test’ is used to check the self-noise and environmental noise of the measurement system. To do this, all sensors are huddled into one location and sense either vertical or lateral vibrations simultaneously.

Huddle test of measurement system at H69

The exercise required a large investment of resource into building, programming, delivering and operating the system on site – but preliminary analysis of the data shows that the exercise was a success and that everything worked. The test was funded by the EPSRC and supported by Tongji University and JSTI.

To find out more about the Vibration Engineering Section, visit our website.


Testing the dynamic properties and performance of a building under human-induced excitation

Emperor House is a modern office building currently under construction at Exeter Business Park, UK. The three-storey building has an internal floor space of 2400sqm, which consists of two wings and a central core.


In collaboration with Summerfield Developments (SW) Ltd (client), WSP-Parsons Brinckerhoff (consultant) and Midas Group (contractor), the Vibration Engineering Section (VES) at the University of Exeter successfully carried out a test of the building’s dynamic properties and performance under human-induced excitation.


State-of-the-art equipment was utilised in the test to identify the modal properties of the first floor of the building and perform extensive walking tests.



The test results will be analysed in detail. The final aim is to help structural engineers to design such buildings at minimal cost, while vibration serviceability requirements are maintained.

To find out more about the Vibration Engineering Section, visit our website.


To find out more about the Vibration Engineering Section, visit our website.

To find out more about the Vibration Engineering Section, visit our website.