Work to fix micro-fractures in the cast iron casings supporting Hammersmith Bridge’s chain saddles could result in the structure being closed to heavy traffic for up to three years.
Hammersmith & Fulham Council has revealed that it closed the bridge to vehicles in April after its engineers found hairline factures in the cast iron “pedestals” that support the chain saddles that carry the 130-year-old suspension bridge’s chain links over its abutments (see diagram below). It says repairs could take up to three years.
The bridge has been closely monitored since 2015, with sensors and weekly safety checks being used to see whether the stresses being imposed on the bridge were causing structural damage. This monitoring found that the bridge’s bearings had seized up because of corrosion and the structure’s flexibility had been affected.
Consultant Mott MacDonald detailed its extensive testing work to New Civil Engineer over a year ago – this work was to inform the council’s decision on the full refurbishment plan.
Hammersmith Bridge north west pedestal crack locations
Now the council has revealed that the latest set back has triggered more investigations. More sensors are to be installed and team of 18 engineers is carrying out another review.
A council statement said: “Our specialist engineers will have completed a full diagnosis of all aspects of the bridge’s state of health by mid-August at which point we will have a more precise understanding of the scale of the works and the timescale required.
“Along with Transport for London, Hammersmith & Fulham Council will then bring forward a detailed plan of work and will be able to give a more precise timescale for the bridge’s re-opening.
“At this stage it is hard to predict how long repair work could take, but it might be as long as three years.”
The problem originally surfaced in 2015 when Transport for London (TfL) said it wanted to route double decker buses over the structure. The bridge had a strict 7.5t weight restriction at the time and a report by Hyder said some strengthening works would be needed for the bridge to support 18t double decker buses. The report said there was some over stressing, and recommended further assessments.
New Civil Engineer’s request for a copy of the recent Mott MacDonald report under the Freedom of Information Act from has been refused on the grounds of security risk. TfL said: “Provision of this information would reduce the opportunity for intervention as suspicious behaviour is more likely to be detected and apprehended if an individual cannot access information about security arrangements and structural information via the internet and instead has to physically visit a site in order to view and assess the security arrangements.”
Hammersmith Bridge has been bombed three times - by the IRA in 1939, by the Provisional IRA in 1996, and by the Real IRA in 2000.
Micro-factures in the north west and south west pedestals under Hammersmith Bridge
Hammersmith Bridge, built in 1887, was the first suspension bridge built over the Thames and was designed by Sir Joseph Bazalgette. Much of the structure is original, with the cross girders, the majority of the hangers and suspension chains all dating back to 1887.
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