Spencer Group were appointed by the Humber Bridge Board to test hangers in areas of high stress on the bridge, as part of the Humber Bridge Board’s asset management strategy. Investigations into the current condition of the existing hangers were necessary to establish the life expectancy of these structural elements. This work allowed the Humber Bridge Board to determine the current life-span of the existing hanger cables, and predict when intervention would be necessary.
|Client||Humber Bridge Board|
Spencer Group were appointed as Principal Contractor and temporary works designer, with Atkins providing project and commercial governance, along with the design of the permanent works.
The bridge deck is suspended from 484no. 62mm diameter inclined hangers with the longest hanger on the bridge being 125m and the shortest hanger at 2.25m.
In order to test the hangers, we removed the specified hanger cables from the bridge and replaced them with new and improved hangers. This was a technically challenging project requiring complex temporary works access and
working within constrained and difficult environments. The project was completed with minimal disruption to bridge uses. The works were carried out only at off peak hours, with no daytime lane or carriageway closures required.
The hangers were tested to destruction by simulating actual fatigue performance and based on these test assessments. The hanger removal process can also be used to facilitate future hanger replacements, utilising lessons learnt to implement the most efficient and effective methodology when the 484 hangers are replaced on the bridge.
Our internal design team designed a bespoke, purpose built access platform to allow engineers to access and inspect the bridge’s hangers. This 4.5m x 3.1m x 4.3m static frame structure provided a safe space to work within, whilst also opening up via an articulating floor to enable the exchange of hangers.
Several challenges were faced on this scheme, most significantly the unknown load in each of the individual hangers, and the requirement to work in line with Historic England due to the bridge’s Grade I listed structure status. Therefore, tight controls were placed upon jacking operations and displacement of the structure, and communication maintained with Historic England.