M4 Viaduct Repairs
Main Steel Sub-Contractor on highly time-critical and high profile repairs on the M4 Boston Manor Viaduct (May to July 2012).
“…a unique repair solution involving the manufacturing of bespoke specialist steel plates and their installation over the crack.”
Highways Agency press release July 13th 2012
Shortlisted as a finalist for the Integration and Collaborative Working category in the 2013 Construction Excellence Awards.
“In addition to the pure resilience demonstrated by the entire team, key to the success was the tremendous respect the project team had for each other and their support for the goal of the project. The stabilisation of Boston Manor Viaduct shows what can be achieved when teams work together coherently, safeguarding the structure and minimising the risk of costly and disruptive closures occurring in the future.”
Osborne Project Report
Ongoing investigations had revealed unexpectedly severe cracks in the steel structure. These had resulted from fatigue due to the age of the viaduct (opened 1965), stress, and some fabrication flaws.
The urgency of the repairs could not have been greater, the viaduct being part of the Olympic Route Network, carrying coaches to and from Heathrow airport and the Olympic Park. Closure of the M4 threatened to remove one of the key arteries for Olympic traffic.
BS Steels was asked to carry out repairs including a mixture of grinding and manufacture of special steel plates to be bolted above and below cracks to the web. Technical and logistical challenges from the highly complex process for the plates were numerous:
- In addition to the bolt plates, filler plates were required on both sides, between the structure and the new bolt plates; these had to be milled to match as exactly as possible the unique profile and undulations of the existing structure. This had to be done for around 30 separate locations.
- The existing structure had to be drilled to highly exacting tolerances. To keep up with demand, drill bits had to be sourced constantly from all over Europe!
- Each plate had multiple tension control bolts, needing systematic tightening; this could only be done during overnight closures, to eliminate traffic loads.
- Continuous re-programming of schedule on a daily basis: need for exceptional communication and collaboration between all parties.
The emergency repairs were completed just in time for the Olympics. The Highways Agency received the following message from the Permanent Secretary on behalf of the Prime Minister:
“I want to pass on my personal thanks to all those who worked so hard to repair the M4 bridge and get it open again in time for the Olympics. You showed real determination to get the job done in time, working through the night to do so. I was delighted to get the news very early this morning.”
You can also download a full project report (PDF) by main contractor Osborne.
The lessons learned through the innovative repair solutions have since been put to use on other locations, notably the M25 Gade Valley Viaduct