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Stratford City Development Bridges

London, UK

º£½ÇÊÓƵ led the design for a series of new bridges to enable the redevelopment of Stratford City ahead of the . The project included the development of two road bridges and a pedestrian bridge, which activated the long-abandoned site by critical connections over significant rail infrastructure.

The new bridges served the athletes’ village and the subsequent Lendlease developments across the site. For road bridges Stratford City Development (SCD) 2 and SCD 3, we were responsible for the scheme design and technical approvals, detailed design and construction support. For bridge SCD 1, the pedestrian bridge, we advised on the initial scheme design before this was progressed separately.

Both road bridges are single span steel-concrete composite structures. The project requirements included a robust and durable structure that could be constructed above existing railway infrastructure, with the railway remaining operational, apart from limited planned possessions. Our engineers came up with a detailed design for the bridge considering durable materials and arrangements that require minimal maintenance, including integral abutments, weathering steel girders, and a concrete deck constructed using permanent formwork. This had the benefit of minimising the future cost and disruption associated with railway possessions for maintenance work.

All the prefabricated steelwork for SCD 3 was erected in a single possession of the railway line, complete with permanent formwork, edge cantilever formwork, and service ducts where possible. SCD 2 had the added complication of needing to span both Network Rail tracks and a High Speed 1 (HS1) track located in a retained cutting. Still, only two possessions were required for steel erection, in recognition of the different railway operators. In addition to reducing disruption to the railway, the short duration of steel erection minimised the period over which large, and costly, mobile cranes were required on site.

The formwork arrangements permitted deck construction to continue without the need for additional possessions. A further feature of the bridges was precast concrete parapets to provide suitable containment over the railway. Our engineers worked alongside the contractor’s precast supplier to develop a practicable arrangement for these elements to exploit the benefits of prefabrication.

A key aspect of our work was advanced soil structure interaction modelling to assess the impact of construction on the HS1 cutting below SCD 2. This led us to design a piled load transfer platform so that the weight of the bridge’s approach structure (a reinforced soil embankment) could bypass the retained cutting and minimise the effects on the high speed railway infrastructure. This was a vital element in the technical approval process we undertook with HS1.

Our ground engineering team also developed a strategy for the reuse of local site material for embankment construction, reducing project costs. This included lime stabilisation, which meant the soils could be processed on site before re-use.

The new bridges provide vital links across the railway that previously separated Stratford City from existing communities, helping to unlock the site. The success of the project was defined by completion in advance of the 2012 Olympic Games. Our design for swift buildability ensured temporary closures of the railway lines were kept to an absolute minimum.