Chapel Street Bridge is a vital component in Network Rail’s £1bn Northern Hub infrastructure upgrade project, which includes the new Ordsall Chord. Located at the northern end of Salford Central Station, it is also the key piece of new infrastructure in the Central Salford Urban Regeneration scheme that will transform the old heart of Salford over the next 15 years.
Ramboll was initially appointed to provide expert advice on strengthening the existing infrastructure. When we concluded that there was a high risk of fatigue fracture under live loading, and high risk of brittle collapse under vehicle impact loading, we recommended replacement. This led to our undertaking the design of the new structure with significant, constrained and very complex engineering works.- Chapel Street, Northern Hub and the Great North Rail Project (GNRP)
- Critical elements identified in assessment of the historic metal bridge
- Designed and built to an extremely challenging programme
- Collaborative design team streamlined the design process
- Preliminary detailed design provided enough certainty to order the steel in advance
- A highly constrained solution
- Ramboll involvement
- Client testimonials
- BCIA award
Ramboll is helping to modernise rail in the north of England by providing vital bridge strengthening expertise for the Great North Rail Project (GNRP). Also known as Northern Hub, GNRP is part of Britain's £1bn Railway Upgrade Plan aimed at boosting train frequency and speed with improved connections in Manchester. The Northern Hub Alliance is a Joint Venture between Network Rail and the delivery partners: Amey; Siemens; Skanska BAM JV; OCR.
In Greater Manchester the new track layout will primarily be on the many historic masonry viaducts that run across the city. Although Chapel Street Bridge did not hold a Grade Listing status it was historically significant for having carried one of the first rail lines through Manchester when it was constructed from cast iron in 1844. Later it was transversely connected to two-adjoining wrought iron flat span structures when these were added in 1890, and all three structures abutted the masonry arch viaducts carrying various rail lines through Manchester.
As Chapel Street Bridge is the central structure of the three metallic bridges at Salford Central, and carries the Manchester Victoria trains over Chapel Street (part of the A6), it was expected to require strengthening for the new track alignments. This is when Ramboll was directly engaged by the joint venture of Skanska/BAM Nuttall to provide expert advice on the existing structures.
The original Chapel Street Bridge structure comprised a single skewed span arch constructed from five cast iron arch ribs with cast iron lattice spandrels supporting cast iron deck plates. Assessment was needed to prepare for Network Rail’s installation of new track between the redundant platforms at Salford Central station.
Through a failure mode effect analysis and a detailed review of the existing assessment, Ramboll’s Advanced Engineering Team, supported by our cast iron materials expert, identified that critical elements of the structure had high risk of fatigue fracture under live loading. In addition, and crucially, the analysis indicated there was a high risk of brittle collapse under vehicle impact loading.
Based on our conclusions, we recommended replacement of the cast iron superstructure. This led to the Northern Hub Alliance employing Ramboll to undertake the design of the replacement structure for Chapel Street Bridge.
The Chapel Street area abounds with structures of historic interest, including the former terminus of the world’s first intercity railway between Liverpool and Manchester, now the Museum of Science and Industry (MOSI). And George Stephenson’s Grade I listed masonry arch bridge lies within the site.
Consequently, a respective bridge design was needed for the bridge replacement at Chapel Street. A modern design in weathering steel was chosen to align its appearance with the Ordsall Chord’s iconic new steel arch bridge over the River Irwell, and to respect the surrounding heritage and regeneration aspirations.
In October 2016, an extremely challenging eight-month programme commenced in earnest. The design package had to complete all design tasks, fabricate the new structure and prepare the existing structure for the six-day rail blockade to replace the bridge. Within this window we also factored in a three-month lead time for the steel fabrication.
Ramboll worked closely with Skanska BAM and the Network Rail project team to agree a streamlined design process whereby the outline design and detailed design ran concurrently following on from the options selection stage. Bringing on board Network Rail’s Delegated Project Engineer as part of the collaborative design team ensured the approvals process was accomplished efficiently and all critical milestones were reached.
To achieve the tight timeframes Ramboll actively drove the collaboration with Skanska BAM ensuring all critical design and construction constraints were identified and resolved early to significantly reduce late design changes. This was achieved through regular design workshops and successful integration of key BIM processes.
During the option selection stages Ramboll developed a 3D model of the existing structures and surrounding constraints from the 3D point cloud survey. This enabled all parties to visually understand the complex constraints associated with the replacement of Chapel Street.
The Ramboll design team utilised the existing infrastructure 3D model to develop the 3D design model. This was one of the key collaboration tools for developing the detailed design with Skanska BAM’s delivery team and the steel fabricator.
Due to the three-month lead time on weathering steel, we had to prepare a preliminary detailed design within the first three months of the eight-month window.
We developed a 3D finite element analysis directly from the 3D model to deliver the preliminary detailed analysis. This process ensured that our preliminary detailed design provided certainty on the dimensions of structural weathering steel required. This meant the Northern Hub project team were able to place the order with the steel fabricator before final approval of the detailed design.
The replacement design for Chapel Street Bridge was a highly constrained solution where stringent constraints imposed by the stakeholders and the existing infrastructure included:
- Comply with demanding track design requirements
- Improve the existing highway headroom clearance
- Use the existing abutment and foundations to support the new superstructure
- Avoid groundworks and critical service disruption and diversions
- Improve the Network Rail’s bridge strike rating for Chapel Street from Red to Double Amber
- Provide a visually respective replacement to the original arch structure
- Mitigate construction activities and programme overrun risk within the rail blockade
The Ramboll team was involved during the design stages and was on-site during the blockade. Our challenges included achieving the early steel order dates, working with, amending and streamlining the assurance process to meet the programme, as well as dealing with late changes to the construction and installation methodology and temporary works.
Our experience in designing solutions for rail blockade construction programmes proved invaluable within the design process of this project, and contributed to the new superstructure being successfully installed during the six-day rail blockade and highway closure.
Ramboll’s design team developed the form and articulation of the replacement structure, along with practical detailing, through positive communication and collaboration with the Northern Hub delivery team leading to a constructible solution.
Thanks to exceptional efforts from everyone within the delivery team, the demolition and replacement of Chapel Street rail bridge was delivered on time and with no disruption to passengers during the rail blockade over Easter 2017. Demolition of the original cast iron Chapel Street superstructure was safely completed in 1hr 15mins. Three days later the new Chapel Street bridge was successfully installed with the main beams bolted together and connected into the existing abutments. The possession was handed back to Network Rail 3.5 hours ahead of time.
During the blockade over 1200 persons project wide were working on site as part of the Northern Hub Easter blockade works, incurring a total of 49,000 hours.
From Mike Heywood, Network Rail Head of Alliance:
It was fantastic to see all the work that had gone into planning and preparing for this shutdown really pay off, and that included successfully implementing a lot of learning from our previous blockades. There was very little variance from the plan throughout the 11 days, and the current assessment is there are no significant scope shortfalls or re-work required, which is great news.
Throughout the shutdown, the expertise of the each of the Alliance participants in their specialist areas was clearly evident, but also alongside this there were again loads of examples of brilliant team work and co-ordination between all the parties. This has undoubtedly been key factor in the success of the project to date.
From Ed Procter, Design Manager, Northern Hub Project (Skanska BAM JV):
On behalf of Skanska Bam JV and the Alliance, please accept this note of thanks to you collectively for the efforts to get this structure designed and built to an extremely challenging programme, which commenced in earnest in October 16. Challenges such as achieving the early steel order dates, working with, amending and streamlining the Alliance assurance process to meet the programme, completing early Cat 3 checks to provide steel order confidence, as well as dealing with late changes to the construction and installation methodology and temporary works were dealt with enthusiastically, professionally, collaboratively and always with the Clients’ ultimate aspirations in mind.
Announcing this project '2018 winner of the Infrastructure Maintenance Project of the Year', the BCIA presenter said :
The designer’s passion for heritage, material and aesthetics made this a stand out project for the judges. A hugely enthusiastic team responded to the challenge of incorporating this new bridge into an already challenging programme, delivering a well planned and executed projected which is now a “shy gem” concealed within the Manchester rail network.