The principal inspection of under deck gantries are conducted on a 6-yearly basis. The findings of which give clients a clear picture of the necessary steps to maintain or prolong the safe operation of these vital pieces of equipment.
Spencer Bridge Engineering were appointed by Amey Consulting to conduct principal inspections (PI) on all 8 of the Severn Crossing permanent under deck gantries and to provide recommendations for corrective actions based on the findings of the PI.
The scope included the 4 main span gantries of the main suspension bridge as well as the gantries on the Wye Bridge and Beachley viaducts. The PI’s were planned, managed and executed in accordance with the protocols prescribed by the IStructE publication.
Prior to mobilisation, the scope was carefully planned by the project team under the technical guidance of the principal engineer.
Spencer Bridge Engineering adopted an ‘in-situ’ inspection approach to deliver significant cost and time savings to the client by removing the need to lower gantries and remove from site.
This approach was made possible by deploying rope access inspection technicians for all over side works, which included both the elevation and under deck areas. The entire structure was visually inspected, with a more forensic approach taken to both areas where defects were founds and areas defined by the principal engineer as being on the critical load path.
In these areas the visual inspection was supported by NDT with surface preparation being undertaken where required. The structure underwent a full coating inspection by an ICORR qualified paint inspector.
As well as the structure itself, all M&E and EC&I equipment was inspected under NIC EIC compliance and the gantries were function tested to review their safe operation over the full range of motion and modes of operation.
Following the site works and gathering of detailed findings, the data was then fed back to the principal engineer who reviewed all of the information, particularly the defects and scored them in accordance with the approach defined in the purple book.
A detailed report was then produced, identifying all of the defects and their effect on the safe operation of the gantry, resulting in recommendations for further review such as design assessments to establish remaining operational life in the current condition, or any remedial works required.
The recommendations were categorised depending on their urgency, allowing the client to be strategic in their approach and prioritise the course of action.
