The redevelopment of Birmingham New Street station is an immense project. More than £600 million is being spent over five years to turn a cramped, congested 1960s concrete box into a light, airy, spacious and efficient station for the twenty-first century.
The Rail Engineer has covered the project several times. In short, the platforms are being decluttered and tidied up so that more passengers can board and alight from trains more quickly. The concourse is being enlarged by taking over the lower floors of the adjoining multi-storey car park and expanding into that space. This will also allow for extra escalators and lifts down to the platforms to ease passenger flows.
The whole centre of the building from concourse level upwards is being removed and a transparent ETFE (ethylene tetrafluoroethylene) plastic bubble roof installed to bring more light into the inner spaces. A John Lewis store will bring new customers into the enhanced retail area on the upper floors, with the Pallasades shopping centre being upgraded and relaunched as Grand Central.
Externally, access routes, taxi and drop-off areas are being rearranged and the whole building clad in swoopy, mirror- finish stainless-steel which will reflect the sky and give the large edifice an almost ethereal quality.
Recently, phase one of the project has been completed. The car park has been turned into an attractive concourse area and public access has been moved into it so that the old one can be closed and refurbished. Passengers are already benefitting from new entrances and a larger retail area, and there is a lot more to come at the end of phase two in 2015.
However, it is easy to become so bemused by the scale of the overall undertaking that the detail is missed. Hidden away is some excellent engineering which, in other circumstances, would form significant projects in their own right.
Richard Thorpe, project director for delivery partner Mace, is well aware that the work of his various design and engineering teams may not be properly appreciated. So your favourite railway engineering magazine made three visits to Birmingham recently to meet Richard and his associate directors and look at these sub-projects in more detail.
Starting with demolition
The first is where the project started, with demolition. Behind the western wall of the existing station concourse was the multi-storey car park in which a new concourse, with a total floor area about 50% larger than that of the current one, would be constructed.
However, car parks don’t have a lot of headroom. To give enough space, a complete floor would have to be removed leaving a double-height space. This necessitated the removal of a concrete floor slab and all the supporting beams which would have to be cut off flush with the main columns.
In total, that added up to a lot of concrete – 7,500 tonnes of it. And underneath the ground floor were the live platforms of the station, so they couldn’t be disturbed.
Local demolition specialist Coleman & Company was brought in to undertake the work. A gantry crane system was developed in conjunction with Mace which could be temporarily installed in the space and would transport cut blocks of concrete to the edge of the building and out through a hole in the wall where they could be loaded onto lorries and taken away.
This technique was a great success. Blocks of up to ten tonnes in weight could be extracted once they had been cut out of the structure. Meanwhile, the enlarging void was stabilised using a forest of bright-orange props and supports supplied by RMD Kwikform, another local company.
Once the entire new concourse area had been opened out, holes were cut in the floor slab through which escalators and lifts would be installed down to the platforms underneath.
Great care had to be taken throughout the process. If a block had been dropped, not only would there be the obvious safety implications but it could have crashed through the floor slab down into the live station area below. So a great many plans were made and the whole process went off without a hitch.
In fact, Coleman & Company made such a good job of it, with its innovative use of the gantry cranes and runways, that it won the 2011 Contract of the Year award at the World Demolition Summit in Amsterdam.
Now for the atrium
Having completed the concourse void for phase one, the demolition team moved on to phase two which involves the removal of the centre of the Pallasades shopping centre above the station to create the new atrium. Another 6,000 tonnes has to come out, 4,000 from the upper roof and 2,000 out of the retail slab, but this time the gantry solution cannot be used as there is no convenient outside wall. Instead, a special machine is being manufactured that will dismantle the main beams once the slabs have been removed by more conventional methods. This will all be ‘nibbled’ away at a rate of up to 50 tonnes per day, and will be removed down an unused escalator shaft.
Before the roof slab can be cut, the steelwork for the new atrium roof has to be in place to support the loads and the ETFE cover installed to provide weatherproofing above the demolition operation. A 400-tonne steel ring beam is being built on the roof, and from this will spring another 200 tonnes of steel arches which will carry the transparent ETFE panels. Of course, this temporarily increases the whole weight of the building by 600 tonnes, so designers Atkins had to make careful calculations to confirm that this could be supported. Some primary columns have been strengthened to ensure that there is sufficient capacity in the structure and a complex temporary works solution developed to support the steel members during installation.
While talking about demolition, it is worth noting that the roof-mounted multi-storey car park, which was to be retained under the initial plans, will be replaced after all. Investigations showed that it was in a poor state of repair. The concrete was full of chloride corrosion, much of which had come from water dripping off cars over many years, but there was also evidence of damage caused by additives in the original material.
As Coleman & Company was fully engaged in the atrium work, DSM was brought in to remove the old car park. It will be replaced, and in fact the new version will have some 450 spaces as opposed to 300 in the original.
Richard Thorpe is pleased with how the demolition is going. “To do demolition and construction works side by side is a very unique experience in construction,” he commented.
Installing a new spine
As well as the wall separating the existing station concourse from the new one in the former car park, there was also the main station service spine. A rectangular construction about six feet high and three feet wide, it ran the whole length of the car park behind the wall at ground level.
With all the new retail and passenger services that the rebuilt station would contain, the spine would need upgrading anyway. And it would have to be moved. So a plan was drawn up to construct a new one, suspended from the retail slab above, farther to the west. It would also include fume extraction, ducted up from the platforms below.
However, plans change. It was decided to fit impulse fans, mounted above the running lines, to drive fumes out of the platform area into the open spaces at the ends of the station. So the new spine wouldn’t need any ducting.
It would still be a major piece of work though. 250 metres long, it would take an estimated 350 men to build, wire, plumb and test it. Contractor NG Bailey suggested that there was a better way.
Prefabricating the spine offsite, in 22-metre long modules, would remove the need for all those people to work in cramped conditions in the roof of the old car park. Also, every system could be installed and tested in a factory environment leading to better reliability and repeatability, as well as workforce safety.
Each module, as delivered, was a steel cage fitted with all the services. It was transported to its final resting place using steel railway lines which spread the load on the concrete slab over the platforms. Hoisted into position, the various cables and pipes were coupled to the previous module and a fire-resistant cladding added.
The idea worked well. The complete spine was installed in a significantly shorter timescale with no defects. “It was a smart way of achieving one of our key installation objectives,” was Richard Thorpe’s comment.
The new spine sits over the central retail area of the new part of the concourse. A riser, also modular, makes the connection to each platform.
The new modular spine isn’t the only one in the building. There will also be a new eastern spine, but as so much can be included in this western spine the eastern one will not need to be as large and it will still be built using traditional methods.
In terms of cost, the original study showed that adopting the new modular method would be fairly cost neutral. However, with the quality and safety benefits, as well as the reduced programme timetable, it has been estimated that the overall cost saving could be as high as 20%.
Just enough room for the escalators
“This is an interesting story,” Richard Thorpe enthused.
The contract to design, supply and fit the new escalators, between the retail level and the concourse and from the concourse down to the platforms, was tendered in the open market using the OJEU (Official Journal of the European Union) system. Stannah won the contract for a system that was designed in the UK but manufactured in China.
The order for 36 new escalators was placed early so that manufacture could take place while the preparatory works were still underway. Chris Gale, Mace package manager, had some uncommon problems to solve. For a start, access to the various locations was severely limited. This not only restricted his ability to bring in the escalators, but he was also hampered by the lack of anywhere to put a crane or lifting equipment.
In addition, clearances were very tight – as low as 5mm in some areas. So the escalators would have to be shoehorned into place.
Once the escalators arrived at Stannah’s York base, testing and commissioning was planned to take 6-8 weeks. Changes in the programme at New Street meant that this was reduced by 20% and the access problems meant that some escalators, such as the pair between the main concourse and the retail floor above, would have to be cut down into three sections and then reassembled using bolted connector plates in situ.
It was a challenge. However, the whole team of Mace and Stannah engineers buckled down and got it done. Stannah managing director David Saunders even went back to his former role as a commissioning engineer to make sure the job was done on time.
The 15 new lifts, supplied by Otis, were less of a problem although constructing the shafts, from platform level to concourse, on live platforms with trains running and passengers everywhere, was a challenge.
Birmingham New Street is an underground station, one of two Network Rail managed stations which are so classified (the other one is Liverpool Street). That isn’t to say it is on an underground railway – it has twelve platform faces, is the busiest station outside London and the busiest interchange station in the UK with a train leaving the station every 37 seconds. However, it sits in a large box below ground level, with the approach tracks emerging from tunnels at both ends and the only way out for passengers requiring them to go upstairs, so it is officially classified as an underground station.
This means it has to adopt similar fireproofing and fire prevention measures as any other underground station. Fire doors, smokeproof cables, fire-resistant cladding and fire-retardant panelling all have to be used at all times.
On a building site, that can cause a problem. One can’t remove a door today and replace it tomorrow – it would circumvent the two-hour fire rating.
The same applies to fire alarm systems. When fitting a new one, the old one hasto remain in full operation until after the switchover. Nothing can be left undone or inoperative, and the live platforms have to be protected at all times.
Consultants Norman Disney & Young advised on a fire strategy. However, this is a skill set that the Network Rail and Mace construction engineers simply didn’t have, not being used to working in such an environment. “None of us have ever been involved in a job that is so intense in terms of fire precautions,” commented Paul Dalton, Mace’s senior project manager.
So Arup was contracted to supply fire engineers for the project. It is one of Arup’s specialities – the firm has 180 fire engineers working on projects worldwide although the New Street team is based in Solihull.
It’s a complex task. Working with Network Rail and the West Midlands Fire Service, Arup’s specialists had to check everything. As the project progressed, however, everyone got more used to the restrictions they were working under and the fire engineers became much more part of the team rather than overseers.
“Risk management, forced upon us by working on a sub-surface station, is about 20% of what we do,” Richard Thorpe explained. “When we changed the concourses over, there was a risk that the new fire systems wouldn’t be stable enough in the first few weeks, so we had a team of fire marshals in place to make sure that there were no problems.”
Tunnels which aren’t tunnels
Risk management was the driving force behind another of Richard Thorpe’s chosen topics. Tunnels, in this context, aren’t the holes in the ground that the trains run in. Rather, they are the pedestrian tunnels which passengers and shoppers walk through and which guide them around the part-constructed station. 140,000 passengers, as well as 40,000 shoppers, pass through the station each day.
There are three such tunnels at New Street. These keep passengers safe from hazards as they cross work areas. And they have to do different jobs.
One guides shoppers from the top of the escalators above the new concourse, through the remains of the old Pallasades and out towards the Bullring shopping centre. It is the longest of the three, but the simplest in terms of construction.
The second leads through the base of the new John Lewis store, the steelwork for which is now up, and takes passengers to and from the entrance on Hill Street. It has a metal roof, tested to be able to resist a scaffolding pole being dropped end-on from a height of 20 feet.
The third is actually part of the station itself. The original plan was to open phase one of the new concourse and close the old one entirely. However, due to the layout of the new escalators, and the fact that each platform at Birmingham has A and B ends (one even has a C), a short train can stop some distance from an escalator. It was therefore deemed necessary to keep the old dispersal bridge and stairs open. This caused a problem, as the entire ceiling, services, old retail units and even walls of the old concourse had to come down. So a pedestrian tunnel was the only solution.
But that tunnel had to go in while the dispersal bridge was open to passengers, or at least while it was closed for five hours each night. The answer was another modular construction. Waco UK, part of Premier Interlink, manufactures modular buildings for a variety of customers including the MoD and the prison service. So they are sturdy and vandal-resistant. Working with contractors Elliott Thomas, a system was devised whereby pre-constructed modules, complete with lighting, two sides and a roof, would be fitted into the old dispersal bridge overnight. Plug-in electrical connectors would power them up. These are now largely in place. Every day, modules are delivered into the old concourse. Once the station is closed, these are wheeled out into the dispersal bridge, positioned and then connected together. Working from the ends towards the middle, three modules a night can be installed in this way.
During the day, passengers simply walk through the new tunnel where it is in place and through the old concourse lined with closed retail units where it isn’t. They almost don’t notice the difference, except that the new modules have better lighting. The last module to be fitted will join the two ends of the tunnel together and then passengers will be safely separated from the work which can then start.
The beauty of this system is that, when the tunnel has to be moved by 20 metres so that work can take place which it currently blocks, the modules can be separated, repositioned and coupled back together again, all over a Christmas or Easter shutdown.
Outside, the stainless steel façade is the most noticeable feature of the new design. Mirror-finish stainless steel panels are already in place along Stephenson Street, and the support ribs are in place around other sections of the building. That, too, was a complex engineering process.
For a start, the swoopy, curved shape means that every single panel is unique. That, in turn, means that its supporting structure is also unique. So every panel, bracket and beam has to be individually made and fitted.
The external brackets bolt back to the building. However, that also had a façade, albeit a concrete one, which is not structural. So the bracketry has to pass through this to pick up a structural wall further back in the building. That places extra loading on the main building, both from the weight of the steelwork and from the wind loading on the finished façade. Designer Atkins had to undertake yet more structural strength calculations.
There was an added complication when the designers wanted to change the fastenings that fix the panels to the structure. This was to ensure a forty year life, based on observation of test panels that had been erected offsite at Bordesley Green. However, this change invalidated the planning permission, so a new application had to be made. That is now in place, and hasn’t delayed the fitting of the panels unduly.
And there’s more…
So those are Richard Thorpe’s top six. There are others. He could have talked about the Green Wall, a vertical flowerbed on a steel frame which includes irrigation pipes that sits alongside the new walkway to Moor Street station.
Or he might have discussed the granite floor tiles in the new concourse. Rough cut in China, these are finished off in the UK to a specification that was arrived at following testing of various finishes and coatings by laying strips in heavily- trafficked pedestrian areas.
And of course the project had to pull in the design and build of the entire John Lewis store building – 250,000 sq ft of top-line retail space that wasn’t even included in the original design for the station.
But six are probably enough for this report. There will be plenty more to report on over the coming two years before the finished station reopens fully in 2015.