When opened in 1981 the Humber Bridge was the world’s longest span suspension bridge, with a main span of 1,410m. The bridge is owned and operated by the Humber Bridge Board (HBB).
The bridge was designed with unusual A-Frame rocker bearings to support the end of the deck at the towers and anchorages, whilst allowing large movements under traffic, temperature and wind loading. They keep the ends of the deck aligned at the towers to maintain a safe and even road surface across the expansion joint that spans between the main and side span deck boxes.
During a special post storm inspection in 2020, the A-Frames at the south tower were found to have significant defects.
Acting as both client and contractor, HBB appointed a team of specialists to perform a series of Stage 1 inspections, structural health monitoring, testing and steelwork repairs.
Information generated by the Stage 1 investigation and repairs informed the design of Stage 2 rocker bearing replacement steelwork.
The deck box shape is complex with sloping sides, inclined end diaphragms and longitudinal slope, which made it difficult to devise a solution that could accommodate the large movements and be installed with the minimum of strengthening and minimum disruption to traffic. New hatches were also needed to facilitate safe access to install the Stage 2 steelwork and improve future access for inspection and maintenance.
The Stage 2 design allowed installation of all steelwork while traffic continued to use the bridge, which kept the duration of the bridge closure required for load transfer to an absolute minimum.
Load transfer to new Stage 2 steelwork was successfully achieved at both towers in less than 4 hours, and involved jacking load into the new steelwork, cutting through the old rocker bearings to take them out of service, and finally bolting anti-uplift steelwork in place.
Mark Bulmer, Director, Long Span and Complex Bridges, AECOM
Mark is a principal member of AECOM’s internationally renowned complex bridges group. Alongside technical leadership of AECOM’s bridge team in Leeds, he provides technical leadership of bridge projects in the UK and overseas. He is particularly experienced in the construction, inspection, maintenance, and refurbishment of long span and complex bridges, and has been involved in more than 40 suspension bridges during his career.
As Honorary Secretary of IABSE (International Association for Bridge and Structural Engineering) UK group, Mark is active in organising conferences, lectures, site visits, and has also authored published papers and articles to share industry knowledge and best practice.
John Collins, Associate, Roughan & O'Donovan
John is an Associate at the civil engineering consultancy Roughan & O’Donovan, based in their Leeds office. He specialises in working with existing bridges. This has included with both the Humber Bridge and Forth Road Bridge, through to cast iron, wrought iron and steel bridges, to masonry arches and post-tensioned concrete structures.
John was co-author of the CIRIA guide Hidden defects in bridges and is currently co-authoring an update to the CIRIA Bridge detailing guide. He regularly speaks at conferences and other events and is keen to share his experiences and learn from others.