M25 Viaduct Strengthening and Repairs

Probably BS Steels’s most challenging project to date! Working with Highways England, Connect Plus and Osborne, we are strengthening the welds on the underside of the viaduct spans on the M25 Gade Valley Viaduct.

The Gade Valley Viaduct, by Junction 20 of the M25, carries the motorway over the Grand Union Canal, the River Gade, a major road and the main London-Birmingham Railway. By any standards, therefore, it represents infrastructure critical to the UK’s economy.

This will also be our longest continuous project, with a dedicated team likely to be on site for several years, and the need to phase work according to traffic needs.

By clicking on the images below, you can inspect a set of strengthening plates, fitted over existing butt welds, under one span (of 10) of the viaduct. Under this span alone, there will be a total of 43 stiffener locations, with some 300 plates and 9000 TCB bolts.

Also pictured, we were delighted to host a visit in January 2018 by West Herts College students, who may well be the engineers of tomorrow.

Preparation for this project started back in 2015, when BS Steels was asked to replicate a 9-metre section of the motorway viaduct, including the existing flaws and imperfections, to enable practice strengthening works ahead of the actual project.

The replica section was then transferred to below the viaduct, in order that trials could be carried out in as true-to-life conditions as possible. These trials established the most suitable treatments for repairs to welds; the safest and most efficient ways of installing doubler plates; and the optimal bolt tightening sequence to achieve strictly controlled torquing values. As each test repair was carried out, non-destructive testing monitored their effects, confirming or refining theoretical calculations.

BS Steels drew on previous experience at the M4 Boston Manor Viaduct, described at the time by the Highways Agency as “a unique repair solution…” (press release July 13th 2012).

M25 road closure report Watford ObserverWe also reported in April 2016 on BS Steels’s emergency response to carry our repairs on cracks found on the same stretch of M25 motorway viaduct.

All around the world, steel structures designed for theoretically long working lives are being found to require repairs much before their expected time. BS Steels has proven expertise in investigations and repairs, and solutions to technically challenging projects. To learn more about our capabilities, please contact Roger Slade by e-mail, or phone 07802 265438.

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