An extraordinary transformation is under way at Birmingham New Street station - with some imaginative engineering solutions to match, as Margo Cole reports.
Birmingham New Street station boasts some extraordinary statistics: over 140,000 passengers pass through it every day, more than double the number it was designed to accommodate. One day last year 205,000 people got on or off a train at New Street. It is the busiest station outside London and the biggest interchange station in the country, and you can get to 95% of all railway stations in the UK from there with only one change.
It is also almost universally unloved. The 1960s-built station, with its dark, underground platforms accessed via an unappealing concrete shopping centre, frequently features in polls of the UK’s worst railway stations.
“What was the station like before? It was awful”
Chris Montgomery, Network Rail
“What was it like before? It was awful,” says Network Rail project director Chris Montgomery, who is in charge of a seven year, £600M project to transform the station and the area surrounding it. “Travellers coming to Birmingham would arrive at a dark, dingy station that is falling to pieces. It was overcrowded, it had a bad health and safety record, and the wayfinding was awful.
“It was no longer fit for purpose,” he adds. “Twice as many people are [currently] travelling through than it was ever designed for, and these numbers get higher and higher. There was also poor access to the concourse and platforms. And from a functional point of view, it was a major constraint to economic growth and regeneration.”
Montgomery is optimistic that the project currently under way will change perceptions of the station by opening it up and making it work more efficiently. The scheme is also intended to be a catalyst for £2bn of regeneration.
The £600M New Street project is the brainchild of Birmingham City Council (BCC), which is working in partnership with Network Rail on the scheme.
“BCC is the bank for the project, and is in charge of things like compulsory purchases, explains Network Rail project director Chris Montgomery. “Network Rail is the operator of the station, and it’s in our interest to coordinate the works and act as developer.”
As the “bank”, BCC has put together an innovative funding package to get the project off the ground, with two thirds of the money coming from external sources including the Department for Transport, former Regional Development Agency Advantage West Midlands, local transport operator Centro and Network Rail itself.
The final third of the funding is coming from borrowing by the council - in accordance with government rules on prudential borrowing - against future income from the new, upmarket shopping centre being built in place of the old Pallasades. “BCC raised the money to buy out the owners, so the project now owns and operates the shopping centre, and Network Rail asset manages it,” explains Montgomery.
“The idea is to regenerate it and bring in upmarket shops, and then sell the head lease at a profit. It’s a very innovative solution.”
The ambitious two phase scheme includes a new entrance; a massive concourse area; refurbished platforms; lifts and escalators to all platforms; an atrium bringing natural light into the whole building; and better pedestrian links. It also includes a complete overhaul of the old shopping centre to take it up market.
New Street station is right in the centre of Birmingham, but its low level tracks bisect the city over a length of around 1.5km, with little capability to cross from one side to the other. The result is a north-south divide, as Montgomery says: “The north is affluent and well-to-do, but if you look to the south, it is exactly the opposite. That is because the station acts as a break, and there is no natural route through it.”
As part of its “Big City Plan”, Birmingham City Council - which Montgomery describes as “the brains behind the scheme” - wanted to redevelop the station and turn it into an iconic city centre landmark with much better permeability, so it can be used to open up regeneration opportunities on the south side of city. “You are going to have five times more space at concourse level, much better access for lifts and escalators, and a high quality station environment with lots of natural light,” says Montgomery.
“There will also be new public space inside and outside; there will be five entrances/exits rather than two, and a 24/7 public right of way to increase permeability and encourage people to use the south side. And it will be a stunning piece of architecture that is a suitable gateway into the second city.”
An innovative funding package has been put together to pay for the improvements (see box), and Network Rail is coordinating the whole project. Back in 2008, the organisation made the decision to bring in Mace as delivery partner.
“Because it is a refurbishment, and because change is inevitable - every time we take down a cladding panel we find something new - we decided to go down a very different delivery route: construction management,” explains Montgomery. “We cut out the main contractor, and employ the subcontractors directly. But for Network Rail to do that, we needed expertise, and Mace brings that expertise.”
He says that Mace also brings knowledge of disciplines that Network Rail may not be so familiar with - for example large scale cladding and atrium construction - as well as an extended supply chain. “Having Mace - who have just built the Shard - on the project - is a real advantage,” says Montgomery.
Work started on site in January 2010 after two years of design and planning, and phase one was completed in April 2013, giving passengers access to half of the new concourse. At the start of the project, Network Rail purchased two floors of a car park that sits above some of the platforms, and in the course of phase one, as Montgomery puts it: “We took out one floor and turned it into a station.”
One of the critical activities on the project is the transfer of load from two sections of the existing roof slab into the new roof structure to enable the old concrete frame to be demolished to form the atrium.
For the most part, the outline of the new atrium follows that of the existing structure, so the columns, beams and slabs inside can be demolished fairly straightforwardly.
However, at the north west and south west extremities the new roof perimeter beam cuts across the corners, leaving two triangles of concrete slab and beams that would be completely unsupported once the internal frame was removed.
So loads from these sections had to be transferred into the new roof beam before demolition could begin.
This has been done by fixing temporary steel beams on top of the concrete beams that were to be cut out. These temporary beams were anchored at one end to the spine beam of the existing structure, and then clamped to the concrete beams at regular intervals along their length using hanger bars.
The bars were then stressed, after which a cut was made in the concrete beam closest to the perimeter beam. A permanent hanger was then fitted to join the concrete beam to the underside of the new steel box girder, and this was then stressed.
At this stage, the loads from the corner sections were effectively transferred, with the remaining sections of beam spanning from
the external frame to the steel box girder - enabling the section of beam inside the box girder to be cut out.
The temporary works solution was developed during the design phase, and took more than a year to plan. Jacking specialist Hevilifts did the stressing, while Tony Gee & Partners designed the temporary works, with the scheme’s structural engineers Atkins and AKTII.
The load transfer operation took place last month, during which Network Rail project director Chris Montgomery said: “We are cutting those beams in half while suspending the concrete from the steel. It’s an incredibly challenging piece of engineering.”
Click here to see a video of the load transfer operation
That is, of course, a massive over-simplification. Removing an entire concrete floor while leaving the columns intact - in order to create a double height space for the new concourse - was never going to be easy.
Montgomery is full of praise for demolition contractor Coleman & Company, which developed an innovative method for taking out the floor. “They put runway beams very close to the columns on both sides, and installed an overhead gantry crane,” he explains. The floor was then propped underneath, and diamond sawing used to cut out sections of slab and beams, which were lifted and carried out of the building using the gantry crane.
“This was a real engineering challenge,” says Montgomery, stressing the importance of understanding exactly how the structure would work throughout the demolition process. “When a 10t block of concrete is moving on a gantry crane, it changes the loading on the building as it goes along.”
Over 90% of the 7,500t of concrete demolished during this process is being re-used elsewhere in the project.
Having created a new concourse area on the west side of the site, Network Rail was able to move all the operational activities of the station - ticket machines, barriers, shops, cafes and waiting rooms - into this area, allowing Mace to swing into action with phase two. This involves constructing the main concourse and new entrance on the east side, and all the new lifts and escalators that will take passengers between the concourse and the newly refurbished platforms. “Phase one was about building the west concourse and getting it to an operational state that would allow us to build the new concourse,” explains Mace senior project manager Paul Dalton. “It had to be functional operationally.” He adds: “The importance of that first move was to get out of the way of the existing concourse, and give us access to that whole [east]side of the station.”
Anyone familiar with Birmingham New Street in its original configuration will be aware that the passenger route to the platforms was from the concourse space, through the ticket gates and onto a long, narrow, enclosed bridge, with stairs and escalators running off it on both sides. This “dispersal bridge”, as it is known, will be replaced by the new, larger concourse once the work is finished. Access to all the platforms will be from the new stairs, lifts and escalators being built within the new east concourse.
Until that section is built, however, passengers still have to be able to get to the platforms via the existing stairs and escalators and must be protected from all the construction work going on around them. Mace’s solution has been to build a temporary tunnel, initially on the line of the dispersal bridge, which separates pedestrians from the construction and demolition activities.
“The beauty of having the tunnel modularised and ‘plug and play’ is that we could bring sections in overnight and open it in the morning”
Paul Dalton, Mace
“The tunnel went in just about the time of the phase one opening,” explains Dalton, who adds that it took around two weeks to build, with prefabricated tunnel sections coming in at night. “It wasn’t always in our thinking as a modularised, prefabricated thing, but the beauty of having it modularised and ‘plug and play’ is that we could bring sections in overnight and open it in the morning.”
The tunnel sections were built using steel frames and Kingspan panels that give the required fire, acoustic and dust-proof characteristics to create a safe, comfortable passage through the construction work going on around it. “The panels gave us a fully enclosed space with all the services in, so we could switch the services off on the dispersal bridge,” says Dalton.
The panel construction also provided protection from work going on overhead, as much of the initial stages of phase two have involved stripping out and demolishing parts of the old Pallasades shopping centre that sits above the station. The 1960s concrete building is undergoing a complete facelift, and will re-emerge as “Grand Central Birmingham” - an 18,000m2, high end retail precinct - when it reopens in 2015.
To achieve this, the old building is being completely stripped back to its concrete structure and entire sections of floor are being removed to create an atrium that brings natural light through to concourse and platform levels, and it is all being clad in a striking stainless steel wrap and topped with a dramatic steel and ETFE roof. As a result, the start of phase two of the project was spent doing a “soft strip” of the old building - taking out all the internal finishes and getting the services disconnected.
“When you chop the centre of a building out, the building wants to collapse in on itself”
Paul Dalton, Mace
“We have been stripping out the services and demolishing old fit-out materials back to the frame,” explains Dalton. “There are old terrazzo and marble floor finishes, as well as concrete screed on the slabs, which have to be removed when - in some places - 100mm below are the overhead lines for the railway.”
He adds: “We had a lot of trouble getting to the services because they were covered in asbestos, so we trained up our M&E contractor to be recognised for asbestos removal.”
Surveys of the existing structure found some defects in the concrete, including, in phase one, some chloride attack on a section of slab on the upper mezzanine level that was supposed to remain in place for the new development. Instead it has been removed and replaced. “We’ve learnt from that, so in phase two we’ve been trying to get into areas early,” says Dalton.
A big issue for the scheme is the structure’s global stability, as the way it is loaded will change in the new configuration, as well as in its temporary state during the work. Atkins has been taken on to deal specifically with the engineering challenges created by the changes to the building’s loadings.
New load characteristics
Although some floor sections are being removed to create the atrium, thereby reducing load, it will have to cope with new load characteristics, including the new roof, which spans the atrium space, and extra load on one side from a new John Lewis department store. “We are taking the existing structure up to capacity,” says Dalton.
One of the more complex areas structurally is at roof level, where the old concrete slab is being removed and replaced by a dramatic new tubular steel and ETFE roof. This roof consists of two elongated domes with wishbone-shaped spines that carry the loads to a steel box girder perimeter beam. This, in turn, transfers the loads to the existing concrete frame, enabling the slab inside the perimeter beam to be cut out to create the first level of atrium space.
However, as the outline of the new roof is a different shape to that of the existing frame, this is far from simple.
Across most of the roof area, the concrete beams supporting the existing slab can simply be cut out, but in two corners, the new perimeter box girder beam cuts diagonally across the existing roof, leaving two triangular-shaped sections of the existing roof slab that will remain in place.
As most of the length of the concrete beams supporting them has to be cut out to create the atrium, the loads from these triangular sections have to be transferred into the new steel box girder perimeter beam before the atrium demolition. This has been achieved with some heavy duty temporary works, including installing steel beams directly on top of the concrete beams that are being removed (see box p23).
The load transfer process was completed in August, and Coleman & Company has started demolition to create the massive atrium that will bring natural light right through the building and down to the platforms. An area the size of a football pitch is being opened up at roof level to create this space.
This process in turn puts different loads into the existing concrete frame. “When you chop the centre of a building out, the building wants to collapse in on itself,” explains Dalton, who says new movement joints had to be formed before demolition could begin.
“We have four very big [train] operating companies here, and when they went into their franchises they had no way of knowing what was in store for them”
Chris Montgomery, Network Rail
Now that the load transfer at roof level has been successfully completed, the main activities on site are the demolition of all floors to form the atrium, creation of the new concourse at ground level on the east side of the building - including installing the new lifts, stairs and escalators - and construction of the John Lewis store - the largest outside London - on the south side of the site.
The platform refurbishment that started in phase one is also continuing throughout phase two. All 12 platforms are being refurbished to make them lighter, less cluttered and more accessible. “We did some early works and found out that the station could work using 11 [platforms], so we could take out one platform at a time,” explains Montgomery.
Deliveries for the platform refurbishment come in by train, with redundant rail sidings on the outskirts of the city having been brought back into use to act as the depot for this element of the work.
Two trains travel between the station and the sidings twice a week, one bringing materials in and the other taking waste out. “It’s great. It keeps a number of lorries off the streets of Birmingham, and it’s an incredibly efficient way of moving materials,” says Montgomery.
Above the tracks
Immediately above the tracks, Mace is managing the atrium demolition and concourse construction. Key to getting the concourse constructed on programme is the need to move the temporary tunnel that was installed last year for rail passengers to access the platforms.
Passengers will carry on using the tunnel until the new concourse is ready, although its initial location - on the line of the original dispersal bridge - is no longer the best place for it.
“A significant amount of the [new] concourse [area] is taken up by where that tunnel is, and it is under the atrium,” explained Dalton just before his team moved it. “Unless we move it we can’t get the rest done.”
Having built the tunnel in prefabricated, modular sections, each with its own services already installed, Mace was able to disconnect, move and reconnect the sections in a new location that opened up the area needed for the atrium and concourse construction - without most of the passengers noticing.
Minimising disruption to passengers, train operating companies (TOCs) and their staff has been one of Network Rail’s biggest considerations. “We have four very big [train] operating companies here, and when they went into their franchises they had no way of knowing what was in store for them,” says Montgomery.
He explains that the project team goes through a “station change” process with each of the operators for every bit of work that will affect them, mapping out exactly what those changes will mean to their business and giving them financial indemnity for anything that has an adverse effect.
He says the ever-evolving nature of the programme means very close liaison with each TOC, setting out how each piece of work will be carried out - such as the temporary access tunnel move - and getting their buy-in. Network Rail has appointed a specific liaison manager for each TOC to manage this process.