[3C1] Assessment of the structural integrity of hidden sewer support structures using guided waves
G P Malfense Fierro¹, S S Bhat¹, J B Elliott¹, K Mullan² and K Vine³
¹The Manufacturing Technology Centre (MTC), UK
²Murphy, UK
³Guided Ultrasonics Ltd, UK
Ageing infrastructure within the UK has increased the requirement for and the frequency of inspection tasks, as catastrophic failure of these structures can lead to costly repairs and, in the worst case, loss of life. One example of such structures is steel sewer hangers, which suspend sewer barrels under bridges/overpasses and are anchored in recesses formed in the above concrete. Some of these structures were built in the 1860s and, whilst they have been updated and rebuilt over time, they face challenges in terms of access and original design. Current inspection of these elements is conducted on the exposed suspension rods by measurement of rod diameters, providing an indication of condition and structural integrity. The difficulty lies in the assessment and inspection of the hidden sewer hanger elements anchored in the above concrete, as there is no direct access. A novel guided wave approach was used to gain insights into the condition of the hidden elements. Three key aspects were measured: the reflection of the guided wave at the hidden element entrance, the reflection of waves within the hidden element and the attenuation of the wave. These measurements were conducted on actual hidden sewer hanger elements and provided the first steps towards defining the inspection procedure and quantitatively assessing the thickness and condition of these hidden elements. Over 40 hidden sewer hangers were tested and characterised as either being in a ‘good’, ‘poor’ or ‘bad’ condition. This work provides evidence of the potential of guided wave technology to be used for novel inspection tasks within the built environment sector.
