Project Ordsall Chord

Location Manchester, UK

Client Network Rail

Expertise Lead designer including civils and Major bridge design in JV with Aecom chord

2018 More than £1bn will be spent on railway Royal Academy improvements between 2014 and 2022 in of Engineering the North of England. One of these ‘Great Major project award North Rail Projects’ is the Ordsall Chord. 2 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 3

Connecting communities and supporting growth

The Ordsall Chord links up three Manchester city centre stations for the first time, reducing congestion and allowing hundreds more trains to run each day.

It is only a 300m stretch of new track, but the Ordsall Chord in Greater Manchester is a piece of engineering that will boost the local and regional economy with knock-on effects felt across a much wider area. The viaduct carrying the track connects existing lines through Manchester’s Victoria, Oxford Road and Piccadilly stations. Accommodating it involved realigning existing track, widening viaducts and laying new track, building new bridges, removing redundant “There is virtually The UK’s first network arch bridge height difference between the 2.5m tall rib section structures and restoring heritage features. All civil The River Irwell crossing is the first network arch and 2.8m tall Trinity Way bridge girder. Brian engineering works were designed by the Aecom Mott no element of bridge in the UK. The structure consists of a tied continues: “The most critical design cases arise MacDonald joint-venture. New public spaces have also repeatability across arch with a network of hangers. This arrangement during construction, when the lattice is incomplete, been created to allow the area’s rich industrial history creates an incredibly robust and efficient structure or if the hangers are accidently damaged or need to be fully appreciated. the different parts – essential for supporting heavy railway loads. replacing. Since the network arch is asymmetric, of this project... a very large number of critical scenarios can The Ordsall Chord connects to the existing Chat “A network arch uses a lattice of hangers to provide develop, which had to be assessed individually.” Moss viaduct to the north and Castlefield viaduct the network arch significantly greater stiffness and robustness than a to the south; both had to be widened. The Chord is totally unique.” conventional bowstring arch bridge, restraining in-plane Building the Ordsall Chord was extremely complex, itself is made up of three components: the River buckling of the arch ribs more efficiently,” explains adds Mike Pedley, senior construction manager Irwell crossing, a concertinaing architectural feature Mike Pedley Aecom-Mott MacDonald JV engineering manager Brian with contractor Skanska-Bam Nuttall JV. “There Senior construction manager known as the ‘cascades’, and the Trinity Way bridge. Skanska-Bam Nuttall JV Duguid. The structural form also makes a significantly was virtually no element of repeatability across The River Irwell crossing is a network arch bridge shallower arch rise achievable, which is in keeping the different parts of the project. Twenty-five with weathering steel arch ribs, while the Trinity Way with the scheme’s original architectural concept. precast concrete arches were built on the project bridge is a 100m long composite steel deck with to support the expanded viaducts. Each one is weathering steel girders. The cascades, also made from Spanning 89m across the river, the arch is made different and the network arch is totally unique. weathering steel, connect these two structures. The up of two ribs that incline inwards 6° to the vertical. Managing that variety was inevitably challenging.” surface of these key members develops a protective The bridge’s composite steel and concrete deck is patina of rust over time, giving the Ordsall Chord suspended via two networks of steel hangers. In The team received the prestigious 2018 Royal its distinctive reddish-brown colour and outlines its elevation, the ribs taper so that their cross-sectional Academy of Engineering major project award in fluid curved shape prominently on the landscape. height decreases from 2.5m to 0.7m along their recognition of the collaboration and engineering length. The cascades accommodate the 300mm skill needed to deliver this project. 4 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 5

The Ordsall Chord

Creating the three-in-one Ordsall Chord viaduct required many other The River Irwell crossing Construction site changes to be made in the area This network arch bridge, with inclined and The network arch bridge (minus tapering ribs, has a network of hangers hangers) was first erected on to support its deck. It is an extremely Museum of temporary platforms in this location stiff structure with a shallow profile. (See Science and before being lifted into position River Irwell Victoria N detail of network arch cross-section) Industry (MSI)

SALFORD The cascades A 16m long curving beam MANCHESTER with profiled web stiffeners Piccadilly continue the ‘crease’ Ordsall Chord line of the River Irwell crossing’s arch ribs Weathering steel

Deansgate Oxford Road

1km River Irwell 3 Castlefield viaduct 1 Built in 1845 and widened 2 as part of current works Middlewood viaduct Built in 1845 and widened as part of current works New public space Stephenson’s bridge Named after engineer George Stephenson’s 1830 railway which was carried Trinity Way bridge N by this bridge, this Grade Web stiffeners applied to 1 listed masonry structure the 2.8m tall girders of this is now part of MSI and has composite steel bridge are been repaired and restored profiled to continue the as part of current works ‘crease’ line of the River Irwell crossing’s arch ribs

‘Ghost’ pier A 19th century steel girder bridge was demolished, leaving just one pier. Its removal allowed essential repairs to Stephenson’s bridge to take place, and opened up views onto the structure Network arch K-bracing cross-section Provides restraint to arch ribs in plan

Tapering arch rib Hexagonal cross- 6° sectional shape exhibiting a ‘crease’ River Irwell footbridge line on elevation Replaces original Prince’s bridge Varies with a 50m long steel structure (14.3m which was designed in 3D and max) delivered as a digital file • The Ordsall Chord will improve rail capacity and Pair of hangers connectivity across Manchester 85, 90 or 100mm • Some 3.2km of track have been altered and 350m diameter solid steel bars of viaduct widened to connect three city centre stations • The project includes restoration and repair of heritage Tie beam structures and creation of new public spaces 15.0m overall 6 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 7

Super model River Irwell footbridge was designed in 3D

Legacy and vision

Ordsall Chord’s Network Rail and its producing a digital 3D model remained under “On the Ordsall Chord, using only a 3D model to contractors came together model of the footbridge the ownership of the JV the fabricator acted as an deliver the structure. This success owes as part of an alliance, over the River Irwell with and gave Severfield an intelligent CAD resource, saved greatly on drawing a great deal to forming a single team that no need for additional intimate understanding of applying expertise in 3D production time and total shared the project’s risks, 2D drawings. design development so modelling, minimising the design cost. the client and rewards and resources. that steelwork detailing need for later rework. It project team’s Key roles were filled Building information developed from the start. reduced both the design “Everything built on this by ‘best-for-project’ modelling The model was also programme and the footbridge including the collaborative personnel, regardless of The Ordsall Chord was used to co-ordinate time taken to prepare nuts, bolts, stiffeners and approach to their employer. Design delivered to BIM Level 2, reinforcement design for fabrication.” The BIM welding, was modelled,” team members took which demands a high and detailing. model included all major explains Brian. procurement on technical approval level of inter-disciplinary structures as well as and project roles for Network co-ordination. Design “The model and drawings foundations and existing “Two-dimensional Rail. Staff from steel and construction data were approved by all underground services. steelwork drawings were delivery. fabricator Severfield were was passed on digitally parties, but were ‘owned’ completely unnecessary embedded in the design to the client for future by the engineer, who River Irwell footbridge because the designer, team, for example, to help asset management. The certified the design,” – 3D design fabricator and future prepare the BIM model 3D model of the network says Brian Duguid. Pedestrian access over asset owner could and steelwork drawings. arch bridge was produced “This is different from the river is via a new 50m interrogate the model. Early co-ordination BIM allowed all aspects of the A willingness to operate by Severfield’s modellers, the traditional process, long steel footbridge. The We worked very hard to structure to be scrutinised in a different way led who were co-located in where engineers usually team decided not to make that possible.” directly to major design the offices of the Aecom- prepare their own generate conventional innovations, such as Mott MacDonald JV. The model and drawings. 2D steelwork drawings, 8 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 9

Network Rail project director Mike Heywood believes that the Ordsall Chord brings together three important features: respect for the area’s heritage, a key piece of rail infrastructure and the prospect of regeneration.

“With many of the people working on the project being local to Manchester, the team had a strong connection with the project and its aims. Having brilliant people and brilliant teams undoubtedly helped make it a success.

“You can have the best ideas in the world, but if you can’t find a way to design and construct them, then that vision will never become reality. On the Ordsall Chord, we trusted each other’s knowledge to make this unique project successful.”

Room to manoeuvre Concrete extensions are not structurally connected to the viaduct

Viaduct widening through conventional strengthened,” says Brian. The skewbacks also BIM enabled the analysis, so cameras and “To accommodate some support precast concrete interaction of new and deflection gauges were degree of movement, arch barrels and spandrel old structures to be used to monitor their we decided to keep the walls, which were infilled carefully considered actual movement under existing viaduct and with mass concrete. All from the outset. The rail traffic loading. The extensions independent this work was carried irregular geometry of results revealed that each and to link them only via out while lines remained the Middlewood and arch behaved differently a slab element within operational. Further Castlefield viaducts – due to variations in the track formation for work was carried out both 19th century brick ground conditions and waterproofing purposes.” during a blockade when arch structures – was the presence of defects in trains did not run. This digitally surveyed and the brickwork. Deflections Construction of these included improvements the data used to plot of between 1mm and concrete extensions to waterproofing their precise shape in 5mm were recorded in first involved installing and drainage before a computer model. multiple directions and 900mm diameter final installation of highlighted the difficulty reinforced concrete piles, the track bed. This was used to develop of connecting the new followed by construction the geometry for the new structure with the old. of in-situ reinforced reinforced concrete arch concrete pile caps and extensions, used to widen “Where the magnitude piers. These supported the viaduct. Behaviour of movement was clearly profiled precast concrete of the original viaduct due to major defects, the ‘skewbacks’ to match the could not be predicted arches were repaired or existing viaduct. 10 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 11

Heritage solutions Stephenson’s bridge could be repaired after an adjoining girder Matthew Nichol bridge was dismantled

Game-changing civil engineering

The Ordsall Chord is part of Manchester’s rich industrial heritage. When it was unveiled to the public in 2017, comparisons were made between it and George Stephenson’s Liverpool to Manchester railway, which crosses the site. Both are considered triumphs of engineering that also support economic growth.

Many of the railway structures that the Ordsall Chord interacts with are listed for historic and architectural significance and part of the site is in a conservation area, so construction had to comply with strict heritage requirements.

“Conservation-led repairs were based on a thorough understanding of the historic fabric of these structures,” says project heritage architect Bernadette Bone. “This ranged from the need to match the type of mortar used to repair brickwork to the choice of materials and their forms to fit harmoniously with existing structures.”

A masonry bridge built for Stephenson’s railway in 1830 has been restored as part of the project. Drainage was improved to prevent further damage to the structure, which carries Grade I listed building Key benefits of the status, the highest heritage protection designation Ordsall Chord in the UK. • New direct links to A steel girder bridge, which had been crudely joined Manchester Airport to Stephenson’s bridge in the late 19th century, was from across the north dismantled to allow full restoration of its northern of England elevation. A ‘ghost’ pier from this girder bridge • Congestion at remains as part of the final scheme. Manchester Piccadilly station reduced by 25%, Bernadette adds: “Stephenson’s bridge, the Ordsall with some services Chord and the River Irwell footbridge connect a pair being re-routed through of piazzas either side of the river. These spaces link to Victoria station new regeneration sites, which have been carefully • Increased capacity articulated so that they respond not only to their • Improved connectivity immediate context, but also enrich the experience • More employment of historic transport structures in the area.” • Better links between new businesses and residential developments 12 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 13

Cascades This undulating feature connects the River Irwell Crossing and Trinity Way bridge

Collaboration delivers innovation

With no precedent for the Ordsall Chord’s asymmetric network arch bridge, the team worked hard to design a structure that was efficient and practical to fabricate and construct.

Rationalising the design of the network arch bridge Constraints perpendicular to the design development, to make them easy to required Aecom-Mott MacDonald to work closely The network arch bridge’s river banks and would detailing had to support inspect and maintain. with Network Rail, Skanska-Bam Nuttall, Severfield asymmetry is due to its need to be built over the architectural concept Their preference was and architect BDP. Temporary construction loads and arch ribs tapering along the new footbridge, of the Chord’s trademark for all steel members permanent in-service forces in the structure had to its length. The complexity while two 7m wide ‘ribbon’ of weathering to be formed from open be understood in meticulous detail to progress the this introduced to the channels below remained steel. A shallow rise sections. Aecom- design to fabrication and construction. Specialist design was exacerbated navigable. This limited for the network arch Mott MacDonald bridge architect Knight Architects was employed by by the need for an options for temporary was also essential. explored a number of the engineering design team to provide additional unsymmetrical support and erection. options to satisfy all advice. Input from Severfield was invaluable in construction sequence. Achieving both these these requirements. developing a single computer model that provided Piers of an existing Prefabrication was aspects was challenging: clarity to the nuances of the structure from the start. highway bridge provided preferred wherever if the network arch rise temporary supports in the possible to minimise was too high, the sag river but were positioned activity on site, but this curve of the cascade skew in relation to the had to be balanced would compromise network arch bridge. with the constraints of the ribbon effect; too Site constraints added transporting heavy or shallow and its structural further challenges. long members. Another efficiency would suffer. consideration was the The alignment of the effect of stresses locked There were also existing railway meant into the structure during additional constraints that the network arch installation and hanger placed on the ribs due bridge could not span stressing. Throughout to Network Rail’s desire 14 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 15

Designed to attract attention Hanger

Inclined Network of 46 tie beam hangers per arch 1200 to 1750mm Anchor

Tapering rib Construction flexibility Pin Crease line Spherical bearings Variable facilitate simpler dimension 14.3m 2.5m H x 0.30 hanger installation 0.7m Crease point Engineering-architecture formed by detail welded 75mm thick clevis 89m H = 700 to steel plate plate for anchor 2500mm integrated into 40mm River Irwell crossing: A network arch bridge thick tie beam web Inclined web

“Our studies revealed Preliminary planning “The design of the effect of simplifying that it would not be drawings suggested a hexagonal shape was fabrication and reducing Horizontal flange feasible for the arch trapezoidal cross-section, the result of combining costs. This crease line is members to be formed but it was decided that aesthetics, structural continued in the shape from an open section,” its flat elevation would performance and of the stiffeners on the Arch rib cross-section detail Inclined tie beam detail explains Mott MacDonald lack the definition fabrication needs,” says Trinity Way bridge and principal engineer Rusi needed to achieve a fluid, Rusi. “The fold in the cascades, meeting the Rusev. “This was due to ribbon-like aesthetic. web plates [creating the architect’s brief for The magic formula The bottom flange is horizontal to facilitate simpler the significant amount crease line] was used visual continuity.” After asssessing many different geometrical forms, erection and deck connection. The resulting section of additional stiffening Working closely with the as a stiffening edge to a good balance was achieved by positioning the has the appearance of a lop-sided I-beam, requiring required, that would be architectural teams, the improve the structural Getting this crease line crease line at 30% of the overall height of the section complex structural analysis to understand the both costly to fabricate cross-section shape was efficiency of the section. in the correct position, and fixing the web at an angle of 7.2° and 22.0°. The stresses in it. and to maintain.” Design modified to a hexagon, as well as developing overall width of section varies from 1200m to 1750mm, effort, instead, was generating a ‘crease’ “By analysing different an overall geometrical corresponding with an overall height ranging from Each hanger network is made up of an inner and invested in improving line, which would draw geometries, we produced ‘rule’ for the hexagonal 700mm to 2500mm. Varying the geometry of the outer set of hangers. Outer hangers are anchored a closed section shape the eye of an observer a design that avoided cross-section, was cross-section creates the desired tapering effect. directly into the web, while inner hangers are for the arch ribs. along the structure. warping. This had the the next challenge. anchored on the inside face of the tie beam. Tie beam conundrum The tie beam was preset and precambered The network arch’s deck steelwork was designed to along its length to compensate for movement meet Network Rail’s preference for open sections. It during construction and ensure that its final is painted a subdued grey colour, so that the reddish position and geometry was correct. “The hexagonal -brown weathering steel ribs are more prominent. shape was the The tie beam is designed in the context of the The asymmetry of the network arch, its complex inclined arches where its web lies in the arch geometry and the need to maintain stability during result of combining plane, with the top flange perpendicular to it. erection greatly influenced the tie beam’s design. aesthetics, structural performance and fabrication needs.” Rusi Rusev Principal engineer Mott MacDonald 16 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 17

Steel tonnage savings The weight of the cascades reduced by 25% during design development

Economies of steel tie beam. Not only did Temporary piers in Contractor Skanska-Bam this save on the amount the River Irwell, which Nuttall split the Ordsall of steel on the project, had been used during Chord into packages, it also provided another demolition of a former enabling conservative level of interest in the bridge, provided support estimates for the amount structure. “We worked for the bridge deck of steel to be calculated as a truly integrated during construction. The early on and purchased team to arrive at this piecemeal erection of the at the best possible price. solution,” adds Jarrod. deck, together with the Severfield worked closely skew temporary supports, with the design team to Innovative installation led to a large number of simplify the geometry of solutions construction scenarios the cascades. These 16m Spherical bearings fitted being analysed to ensure long fabricated beams in the hanger anchorages safety. Weight and lifting with welded stiffeners provided extra tolerance restrictions meant that were designed in 3D. for erection and the twin arches had to hanger installation. be lifted from third-points “Working together, the Approximately 1.5° instead of from their weight of the cascades tolerance is provided ends, as would be more was reduced by 25%,” by bearings in each common. Temporary explains Severfield senior anchor. This absorbs cables restrained the project manager Jarrod up to 0.5° installation arch ends until the arches Hulme. “Initially, the tolerance and 1° in were fully connected. design included a twisted fabrication and erection. form, but this would “The in-service design have been expensive to Mott MacDonald design of this bridge was fabricate. Together, we team leader Tim Abbott challenging, but not revised the stiffening explains that these nearly as complex as features. Welded onto bearings also provided the construction-phase the cascade’s beam, more flexibility for analysis,” comments these take on a strong the final construction Rusi Rusev. Changes to architectural role, with sequence, which required the erection sequence their spacing and shape the network arch bridge were checked on a varying as the beam to be built piecemeal in versatile analytical curves and tapers. This its final location, rather computer model and on gives the Ordsall Chord than assembled nearby detailed local models at its amorphous quality.” as a complete structure critical locations during and slid into place. development stage. Elsewhere, instead of increasing the thickness “We had to build the “The success of this of the tie beam’s web bridge in parts because project is very much a from 40mm to 75mm to of site and programme product of the effective accommodate the clevis constraints. This had and open collaboration plate in each hanger’s enormous implications between the designers, anchor, it was designed for the design of the erector and fabricator. with a cut-out. This structure, hanger The use of a global “The success of this project is very allowed the thicker clevis stressing sequence and BIM model facilitated plate to be welded to the arch behaviour,” he says. that collaboration.” much a product of the effective and open collaboration between the designers, erector and fabricator.” Rusi Rusev Principal engineer, Mott MacDonald 18 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 19

Levels of detail BDP head of transport Peter Jenkins conceived the curved form of the Ordsall Chord, although the final design was the result of a collaborative process. “The design changed over the course of the project and together we added value, but the silhouette of the design was always honoured,” he says. The architect adds, “I think the design is better for it. There is a richness which has been added through the detail – you can enjoy it from a distance and even more as you get closer.”

This is evident in the tie Stressed out Temporary cables beam and clevis plate supported the arch before connection and on the hangers were installed cascades. He explains that the varying spacing of fins on the cascades creates an extremely tactile form. “Looking at it you’re compelled to run “There is a richness Bridge building construction manager at was safer, reduced and after the deck was your fingers over the fins,” On a world’s first Skanska-Bam Nuttall. temporary works over concreted. New track says Peter. “That quality which has been project, there is Each arch rib was the river and resulted in and other rail features is more common in added through always the possibility fabricated in six sections, a higher quality product. were then installed. building design than civil of encountering and welded together in It also saved between engineering, which makes the detail – you the unforeseen. the horizontal position three and four weeks Trains are now using the it all the more special on can enjoy it from Hanger stressing, on low level supports on on the programme.” Ordsall Chord, enabling this project.” although carried out the banks of the river. The alternative was to more rail journeys to be a distance and systematically from build the deck across the made across the city. even more as the centre and moving With K-bracing, temporary river first (on temporary The project is already out to the ends, was struts and other bracing piers) and then erect benefiting businesses you get closer.” a particularly nail- installed, the ribs were falsework on top to and the travelling public Peter Jenkins biting experience. then rotated to near- support construction of across the north of Head of Transport, BDP vertical and lifted into each arch member. England and beyond. “With temporary supports position using two of the This engineering located asymmetrically, largest crawler cranes The risk of working at masterpiece will continue deck behaviour was in Europe. “We chose to height coupled with it to have a positive difficult to predict do it this way because taking longer to access, effect on this area for during construction. The we wanted to avoid ruled this option out. After generations to come. deck was designed to the risks of working at the network arch had lift off during hanger height – it was tricky been lifted into position, installation,” says enough welding it on hangers were installed Mike Pedley, senior land,” recalls Mike. “This and stressed before 23 I Mott MacDonald I Ordsall Chord Ordsall Chord I Mott MacDonald I 24

Opening opportunities with connected thinking.

Talk to us: [email protected] Search Mott MacDonald rail and metros