In comparison to the extremely visual viaduct that strides during the Colne Valley and the military of concrete piers marching against Birmingham’s new HS2 terminal, the constructions of the Delta Junction were retaining a low profile.
Contractor Balfour Beatty Vinci three way partnership (BBV) has been often progressing Lot N2 at the japanese flank of England’s 2nd town for 5 years with little or no fuss, construction a 10km community of railway viaducts, embankments and cuttings. Particular person bridges could have attracted consideration with their high-profile building strategies, however the scale of the total scheme is itself worthy of notice.
From a bridge engineering point of view on my own, the presence of 13 primary viaducts, of 3 other structural sorts constructed the use of a myriad of building strategies, units it up as a text-book instance of ways infrastructure may also be woven round current delivery hyperlinks with little disruption. The web page is equipped through an enormous precasting backyard that since June 2023 has became out just about 3,000 deck parts at a top price of 36 each and every week.
The Delta Junction is composed of 3 primary rail corridors: the Birmingham Spur, which peels off the primary HS2 line to hold trains to and from Curzon Boulevard station terminus within the centre of the town; the Delta Mainline, meant to hold trains direct to Manchester; and the North Chord, which brings northbound trains from Curzon Boulevard again to the primary line.
Each and every of those corridors has to skip over, underneath and round rivers, railway strains, streets and motorways whilst making the least imaginable have an effect on at the surroundings and different travellers.
This current infrastructure was once the place to begin for choices on what form of constructions could be hired the place, in response to the span lengths required and the urge for food for highway or rail possessions.
The place lengthy spans are vital (Water Orton viaducts jump over the M42 toll road on 45m-long spans) an important effort has been made to maximize repetition of those span lengths and structural sorts in order that the most productive use might be product of the specialist apparatus vital for precasting and building.
Therefore Delta Junction options no fewer than six precast segmental viaducts, two of them neatly over a kilometre lengthy. To house the various bodily and environmental calls for, the contractor is the use of 3 other tips on how to construct those constructions.
Like lots of the bridges at the challenge, they’re named in pairs – Water Orton One and Two at the North Chord, the longest of the six at 1.3km and 1.4km respectively; River Tame East and West on the north finish of the Delta Mainline; and Coleshill East and West, which shape the junction interchange the place the Birmingham Spur peels off the primary line. The primary line has 4 rail strains whilst the opposite chords of the triangle each and every lift two strains, so viaducts range in width relying on the place they’re positioned, some wearing unmarried tracks and others double.
An additional 4 crossings are composite viaducts – with metal beams introduced or craned into position and urban decks forged in situ – and there also are 3 low-level viaducts constructed on in situ concrete piers, with decks shaped of precast, prestressed concrete beams and deck planks.
Many of the spans for the precast segmental viaducts are being erected through balanced cantilever building the use of a brief mast and cables to switch the balancing forces, and a pillar-jib, or ‘swivel’ crane to manoeuvre segments into position. It’s the primary UK challenge the place this kind of building has been used, despite the fact that it’s somewhat not unusual in different places.
The primary and final spans on each and every of the precast segmental viaducts are constructed through assembling the segments onto a 42m-long, 6.5-tonne metal body made of 2 metal beams prior to stressing them in combination. The metal body compensates for the loss of a balancing span.
As BBV building director David Waite explains: “We crane the segments into position at the beams after which we prestress the span in combination, jack it up to take away the truss, then decrease it right down to its ultimate place.”
The approaching Christmas blockade of the railway has been in making plans for greater than two years now, so its arrival might be a specifically welcome milestone for the group. The primary function all over this ownership is to proceed the Water Orton viaduct over the native railway, a procedure this is best permissible with the road closed.
The balanced cantilever way comes to a brief metal mast that rises 22m above the deck, and a 14m tall ‘swivel’ crane mounted as regards to the forefront of the deck. With such large-scale {hardware} on show, there may be glaring possible for distracting drivers, one thing stakeholders need to get rid of.
“We’re nonetheless construction the previous couple of piers at Water Orton, the use of the normal in situ way with metal shutters,” studies BBVJV senior challenge supervisor Nicolas Gallone. “The purpose is to achieve the north facet of the Birmingham/Nuneaton railway line forward of the blockade which begins on 23rd December for 125 hours,” he provides.
The 3rd building way for those segmental viaducts will come into use subsequent summer time when the six Water Orton Viaduct spans that lift HS2 over the M62 might be wheeled into position all over a weekend toll road closure.
As Gallone explains, this operation should be meticulously completed: “We can use the metal truss once more to gather those spans along the toll road in order that they’re in a position for the street closure.” As soon as jacked as much as operating top they are going to be pushed on self-propelled modular transporters to the pier places, transferred onto the piers and stitched in combination.
Maximising the usage of the bigger spans was once BBVJV’s distinctive promoting level, Waite claims. “Clearly it’s worthwhile to use a sort traveller to build those spans, however Vinci’s proposal was once to make use of precast segmental viaducts and stay repeating that span period as again and again as you’ll.
“Upon getting were given the precast backyard arrange it is sensible to have a look at the place else you’ll use it. On Coleshill Viaduct we will have used a 30m span however because it’s in a flood undeniable, it’s highest to stay the footprint of the bridge as small as imaginable to maximize the flood capability.” Having a modular design made it imaginable to evolve to other span lengths.
4 ‘kits’ – each and every of which incorporates a metal mast, a swivel crane and a self-propelled modular transporter – are in use for the precast segmental viaducts. They’re provided with deck parts from the Kingsbury precasting backyard at Lea Marston, which is 3.5km from the closest and 6km from the furthest bridge. Laydown house is to be had at each and every viaduct, enough to have sufficient gadgets in hand to construct two spans, Gallone says.
The primary of the precast segmental viaducts to be constructed was once the 472m-long single-track River Thame West crossing, which was once finished in February 2025. Paintings began at the viaduct piers in 2023, and urban deck building adopted within the spring of 2024.
As soon as the single-track viaduct deck was once finished, paintings switched to erection of the deck for the double-track crossing. The general public carrier automobile bridges are concentrated at this interchange, together with the 2 longest, so naturally the package and body of workers assets are steadily being relocated right here because the decks of the shorter constructions succeed in crowning glory.
“At the Tame viaduct the place the deck is entire, we at the moment are doing the 3rd wave of task – construction the entirety above the deck, including the architectural precast parapets, sewing them, casting the kerb and including all of the walkways, cable containers and waterproofing and so forth,” says Gallone.
“In this day and age we now have two kits of apparatus at the Coleshill East unmarried tune viaduct and the Coleshill West double tune viaduct,” he says. The aim is to transport those two kits to Water Orton within the new yr so all 4 kits might be to be had for a last deck building push.
Since manufacturing started in 2023, the precast backyard has became out some 90% of the two,742 gadgets wanted for the segmental decks, with the final ones because of roll off the manufacturing line originally of 2026. However the backyard gained’t be dismantled simply but; it is going to be tailored to produced precast deck planks for the superstructure of any other of the three way partnership’s contracts – the viaducts that lift the railway into Curzon Boulevard Station.
In the meantime, the precast concrete beams for the Delta Junction viaducts are being forged at a purpose-built manufacturing facility in Melton Mowbray.
“At Kingsbury we now have 9 shortline beds facet through facet, and each and every of them has 4 positions, so in a regular week we’re ready to fabricate as much as 36 segments,” Gallone explains. “Each and every place can be utilized each for standard segments and particular ones, similar to the ones for the pier best or abutment the place the association of reinforcement and post-tensioning ducts could be very particular. The density of rebar is going as excessive as 460 kg/m3 of concrete, so the pieces that wish to be embedded need to be positioned into the
shape with nice accuracy,” he provides. Fit casting is used, therefore each and every deck component should be sparsely labelled to spot its ultimate place.
Such density of inclusions calls for a concrete combine with microaggregates that may be simply compacted into the gaps. In step with Waite, the backyard has no longer needed to scrap a unmarried phase after concreting has begun: “We’re very proud that we’ve by no means misplaced a phase that we’ve began casting!”
Cautious control of the shortline beds is an important to stay the tempo of manufacturing, and Gallone notes that the usage of the Maturix real-time concrete tracking app offers engineers the arrogance to authorise hanging and shifting of gadgets with out depending on energy check effects from exterior laboratories.
“Each day you need so to forged any other phase, so the concrete must be cured and with enough energy to permit it to be lifted out and positioned within the garage strains through the gantry crane, freeing house for the following one,” he says.
“We evolved the adulthood curve consistent with the other temperatures, the core temperature of the concrete, the dimensions of the solid component and so forth, and use thermocouples forged within the parts to relay information to the app so we will be able to correlate them with the ones curves. Our engineers can then make a decision when to strike formwork.”
The backyard may be set as much as save you the ambient temperature from affecting manufacturing, as Waite finds. “We will tent it over, and we’ve were given heating in there so we will be able to lift on operating during the iciness,” he says. “Our batching plant additionally has a chiller on board – it’s value having it right here as we’re the use of such a lot concrete, no longer just for the casting backyard but additionally to offer different belongings.”
A 2nd machine, referred to as Verifi, is used to analyse the traits of the concrete within the drum and get rid of the will for a stoop check with each and every batch. “We nonetheless now and again do samples and assessments to substantiate that Verifi is right kind, however no longer for each and every batch,” Gallone says. “Verifi has accelerated the method of pouring the concrete and Maturix has accelerated the method of hanging and shifting gadgets.” Each Maturix, evolved through Danish start-up Sensohive, and Verifi, a US innovation, at the moment are owned through Saint-Gobain.
New apparatus has additionally performed a central section in making improvements to protection within the building of the bridges, together with the advance of a different spreader beam for lifting deck parts, and a robot unit for dealing with the jacks which can be used for stressing the strands throughout the deck.
The phase lifter is an automated spreader beam designed to suit to the openings forged within the best of the precast deck gadgets. It’s deployed each at the gantry crane within the backyard and at the pillar jib cranes on web page, enabling the concrete gadgets to be lifted and treated simply and safely.
“Conventionally that was once carried out through any individual mountain climbing as much as repair chains and lifting take on onto the phase,” says Waite. “That procedure has been eradicated, making the operation more secure and sooner.”
The robot multi-strand jack handler is much more spectacular, getting rid of the awkward handbook dealing with this is most often vital to hold out the post-tensioning operation inside the field girder.
Gallone explains: “We use very heavy compact multi-strand jacks that weigh as much as 1.1 tonnes and our personnel need to take care of those jacks throughout the field girder, shifting them from span to span and lifting them to hold out the stressing of the bundles of as much as 31 strands.
“The robot unit is a chassis on articulated bogies with an articulated arm and the entire unit is radio faraway managed. It weighs nearly 2.2 tonnes in general, and is moved throughout the deck to the desired place, the place the arm is deployed through the hydraulic cylinders spaced alongside it. The multi-strand jack this is used to fret the strand package deal is mounted on the finish of the arm.
“We now have 4 of those machines, one for each and every package, and they’re remotely managed through the operator,” Gallone provides. Conventionally this process would contain jacks being manually treated through operatives in confined areas the use of a block and take on.
The concept that for the gadget dates from the Eighties, finds Gallone, however at the moment the builders may just no longer get it to paintings as they sought after it to, so it was once shelved. Adjustments in era, coupled with the opportunity of in depth use on HS2 supplied the vital impetus to revisit the theory, and HS2 marks its first authentic deployment.
The one sadness for Gallone is this nifty piece of apparatus is tucked away throughout the field girder, depriving it of the eye it merits.
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