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

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.

DCIM101GOPROG0020013.
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.

DSC_7707
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.

 

DCIM100MEDIADJI_0152.JPG
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.