Spencer Bridge Engineering were appointed by the Humber Bridge Board to undertake hanger testing in areas of high stress on the bridge as part of its asset management strategy. Investigations into the condition of the existing hangers were necessary to establish their remaining service life. The results enabled the Humber Bridge Board to accurately determine the current lifespan of these critical structural elements and forecast future intervention requirements.
Spencer Bridge Engineering 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 484 no. 62mm diameter inclined hangers with the longest hanger on the bridge being 125m and the shortest hanger being 2.25m.
In order to test the capacity of the hangers, the team removed the specified hanger cables from the bridge for testing and replaced them with new and improved hangers. This was a technically challenging project requiring the development and implementation of intricate temporary works and access solutions within a constrained and challenging environment.
The project was completed with minimal disruption to the bridge, as works were carried out during off-peak hours, with no daytime lane or carriageway closures required. The hangers were tested to destruction by simulating fatigue performance, and from these tests the remaining service life of the hangers was determined. The removal process also informed future hanger replacements, applying lessons learned to develop the most efficient methodology for the eventual replacement of all 484 hangers.
Spencer Bridge Engineering’s design team developed a bespoke access platform to enable inspection of the bridge’s hangers. The 4.5m x 3.1m x 4.3m static frame provided a safe working area and incorporated an articulating floor system for removal and installation of hanger cables.
Key challenges included the unknown load in each hanger and the requirement to work in line with Historic England due to the bridge’s Grade I listed status. To address this, stringent controls were implemented during jacking operations to manage load transfer and structural displacement, while communication was maintained with Historic England throughout the project.
