Macrete’s concrete Flexiarch is being used to strengthen Tameside Council’s Jubilee Bridge, which spans National Cycleway Route 66 in Greater Manchester. NCE reports.
Tamseside’s 88 year old Jubilee bridge, named to commemorate the silver jubilee of King George V, had been weakened by extensive steel reinforcement corrosion and spalling concrete before engineers from Tameside Council took action to solve the problem.
In December last year, 14 Macrete Flexiarch units were slid into place beneath the bridge in the product’s first application as bridge reinforcement. The 7.4m span flexible precast concrete arch ring units were manufactured in Northern Ireland and shipped to site in four deliveries over two days.
The arch rings arrived on site as a flat strip and were then constructed as a series of tapered precast concrete units, linked on their upper face by a bonded flexible membrane allowing the arch to be formed as it is lifted from the transporter.
Each arch ring was craned into position onto laterally extended cast insitu cill beams, to which grease was applied. They were then slid beneath the bridge structure using a pair of hydraulic jacks.
“Spalling concrete and corroded reinforcement was caused predominantly by carbonation and chloride attack”
Peter Robinson, Tameside Council
They were moved to the far end of the 14m width of the old bridge, until all 14 arch rings were installed - a process that took 36 hours.
“Our engineers have become increasingly aware recently of problems due to spalling concrete and corroded reinforcement on the Jubilee Bridge caused predominantly by carbonation and chloride attack,” says Tameside Council executive member for transport and development, councillor Peter Robinson.
“The application of sprayed concrete to the bridge deck soffit in 1974, in retrospect, has made it far more difficult to assess the full extent of the problem. Wilde Consulting Engineers suggested using the Macrete Flexiarch system to provide the best value for money solution,” he says.
Wilde considered five options, including demolishing and rebuilding the reinforced concrete bridge deck, before coming up with the Flexiarch solution. The bridge has cost £420,000 to repair and now has a design life of 120 years.
The main contractor for the project, AE Yates, is due to complete the bridge refurbishment on time and to budget next month after 16 weeks on site.
To do this, new spandrel walls are being constructed insitu. Workers will then drill through the existing road surface and bridge deck before pumping foam concrete into the void between the old and new bridges.
The road will then be resurfaced and new parapet walls constructed.