On 5 October 2010 the historic Hastings Pier was set on fire, destroying 95% of the Grade II listed building and leading to concerns over its future. Now NPL's material scientists are helping to show that the future of the pier is more positive than expected.
Hastings Pier before and after the fire
Prior to the fire, NPL had been surveying the pier to support redevelopment plans and to monitor long-term changes in the pier. The project was part of the development of a world-leading low-cost technique (Digital Image Correlation) to assess long-term degradation of structures.
Following the devastating fire, NPL scientists returned to Hastings to take their second set of photos. They were then required to develop more advanced analysis techniques, which could deal with the much larger than anticipated changes to the pier, and produce meaningful information about its structure.
Digital Image Correlation
Digital Image Correlation is used by NPL to look at civil engineering structures. The process works by taking ultra high resolution panoramic photos – images up to 1.4 gigapixels in size - at two different times to identify structural changes. Advanced mathematical programs then analyse the pair of images to identify changes in the structure pixel by pixel. Using this information, engineers can understand how large structures change over time.
For Hastings Pier, up to 45 images were stitched together to produce an ultra high resolution final image 80,000 pixels wide - 300-400 times more detailed than a typical camera-phone photograph. Processing these images, one before the fire and one after, can help highlight where the structure has apparently changed.
In the case of Hastings Pier, results have been very positive. Whilst the superstructure has been severely damaged and there are large visual changes, the cast iron framework - or substructure - seems much less affected. The substructure on the west side of the pier appears to be remarkably similar before and after the fire. On the east side there are small areas where there are some changes, and one localised area of the substructure about halfway along showing significant distortion. But the vast majority of the substructure seems largely unchanged. The area showing the most distortion - presumably caused by the extreme heat - was at a downwind point where the fire was reported to have been fiercest.
The project has also helped prove the concept of Digital Image Correlation for the measurement of changes in large structures, by providing NPL with a real-life case study enabling development of key analysis software.
Beyond the Pier
Digital Image Correlation is just one of a number of techniques that NPL is developing for low-cost examination of large civil engineering structures such as bridges, buildings, tunnels and piers. Digital Image Correlation allows the computer to effectively carry out the laborious checking of the whole structure. This means quicker and cheaper identification of areas which have been deformed or damaged, and hence may need closer inspection. This is important on large structures such as piers as it allows civil engineers to focus their efforts on the parts that most need attention, dramatically speeding up the inspection process and reducing the cost of repair.
Source: NPL, Teddington, London