Adjusting for inflation, Crossrail will cost about £16 billion. With 42 kilometres of new tunnels under London and nine new stations, Will Stirling assesses how Building Information Modelling is helping the project both stay on budget and reduce whole life costs.
Phyllis and Ada, tunnel boring machines with near celebrity status, bite and slice their way rock and mud at 100 metres a day. Engineers calculate routes to lay electrical cable and pipes while dodging the spaghetti of old cable and vents that snake under London’s streets, while cranes maneuver prefabricated tunnel sections into place. Hundreds of workers swarm from ground level to 40 metres underground in Europe’s biggest infrastructure project.
Crossrail is the biggest works on the London Underground system for 50-years, costing the Government, the Mayor of London and London businesses £15.9 billion at the last estimate.
Apart from its sheer scale and complexity, Crossrail differs from other big public works projects in its use of BIM, or Building Information Modelling. BIM uses multi-level data rendered in a “3D common language environment” so that the interdisciplinary parties in this project – architects, structural engineers, mechanical and electrical (M&E) engineers, designers and manufacturers – can talk about exactly the same thing and, crucially for so many participants, visualise it in 3D.
BIM is used in civil engineering projects all the time but Crossrail has set about using it “enterprise-wide”. The alternative is sharing a mish-mash of 2D and 3D data, derived from different software platforms and labelled in many different ways.
Fans of BIM say that its benefits are numerous. As well as the cost and time savings realised from fewer design iterations, common labelling and better visualisations, BIM should theoretically reduce the project’s whole life cycle well beyond the construction phase.
“Crossrail has taken on what the ODA [Olympic Delivery Authority] did at the Olympics with BIM,” says Nick Hoyle, chief engineer, Technical Solutions at Balfour Beatty, the prime contractor for two Crossrail sections, C510 and C512. The Olympic Games were also BIM-enabled, but Crossrail is takes “single source of truth” even further through the introduction of BS1192, the British Standard that demands standardised labelling of parts and terms in the construction industry, introduced after Crossrail commenced build in 2009.
Mr Hoyle, a BIM evangelist, illustrates why labelling, among other benefits of BIM, can make a simple but key difference in a civil project. “For [engineering work on] Blackfriars Bridge, Network Rail called it Span 1, Span 2 through to 5, numbering from the south bank. Port of London Authority called these Arch 1 to 5, from the north bank. Is this a common language? When BIM is used in all public procurement, the advantages will be massive.”
Why is BIM needed for Crossrail? Surely thousands of large civil projects have been delivered, if not always on budget, in an organised way using the old system of multiple data source and flow. “Normally on a typical site you have one architect, one designer, one contractor etc and the use of BIM is quite straightforward as people collaborate and information is shared,” says Malcolm Taylor, head of technical information for Crossrail. “A typical Crossrail station will have dozens of contractors and multiple designers all needing to design and build in the same physical space, and BIM organises how that is done in a virtual world before it takes place in the real world.”
WLC, not capex only
One of the main principles of BIM, rather like Through-Life Engineering in the mechanical engineering world, is to reduce whole life costs. Mr Taylor says that BIM is forcing the project team to think about the operations cycle. “You barely see the [operational] standards for London Underground for whole-life costs mentioned in the project specifications [quotes]. Standards generally have huge assumptions that whole life costs will be considered [by the construction phase] but they generally do not take them into account. In a BIM world you are ultimately going to be able to see that movement of data and information up and down the cycle in a much better way in 10-years’ time.”
The idea is to save money at the opex, the operations and maintenance, end of the project. While accountants in a big public works traditionally tend to be more focused on the upfront capex, says Mr Taylor.
“Consider that capital cost of the building I’m in now is only 25% of its total lifetime cost, and that the data generated in the beginning was almost certainly never brought into the project for operations and maintenance,” he says. “That’s why I’m so convinced that BIM is right, on PFI [private finance initiative] projects, where the O&M costs are so upfront on Day One it’s untrue. In a typical public works you never get that.”
Does BIM save Crossrail money?
A fully BIM-enabled project might increase the upfront capex by a few per cent, experts say. Over the life of the build, however, BIM begins to claw back costs, a clear example being where it helps design components where existing “as-built” designs are incorrect. Nick Hoyle says “At the Durward Street shaft, we designed an alternative temporary works design for a propping system, because the requirements were very different from the original system design.” BIM, he says, helped with the design of this, by analyse the existing design using 3D BIM software, and “being able to iterate that several times from a common data base.”
Malcolm Taylor says: “[The construction industry] knows from studies done, especially in the US and in the UK now, that if you are smart about the way you share information as it moves through the stages from concept through construction to operations, you can start to hit 15%-20% savings in infrastructure costs and efficiency in the longer term.”
Visual validation
BIM has two big advantages, says Balfour Beatty’s Hoyle. “It allows you to iterate designs much faster using digital technologies, and its ability to communicate these to the client and their designers etc, using a simple 3D model is critical in getting adoption.” This visual validation is an important part of BIM. Hoyle has worked for Balfour Beatty for 26-years and can “immediately see a 2D plan as 3D”.
Other parties, especially clients, are not always so gifted in the virtual sesne. “Imagine this: walk one mile to the south, a mile to the east and a mile to north. You’re not back where you started, that’s easy for many to see. But do this at the North Pole and you are. By showing people the interface of multiple parts and materials on a sphere, a 3D object, it is easy to imagine, but not on 2D a map.”
How does BIM affect the manufacturing for Crossrail? Hundreds of suppliers feed the mega-tunnel and, owing to its complex procurement process, it is difficult to confirm how many of these companies use BIM in their product designs. In housing construction, BIM encourages more offsite manufacture because a common language project should minimise the number of measurement errors in assembly.
“A key thing [for offsite manufacture] is you have this interdisciplinary check early on,” says Nick Hoyle. “Because [the component] has the same XYZ coordinates as the designer, when you model it and compare it on plan it means you can look at safety and methodology, and spot any clashes with the existing infrastructure. It enables manufacture for construction, and it increases the chance of right-first-time.”
While a BIM-enabled project might increase capex upfront, the end-game for BIM in Crossrail is the time and effort this single source of truth will save the operations customer, Rail for London. Fewer episodes of taking the right component to the wrong signal box.
The Deepwater Horizon spill bears a telling example of this, when the rig operators built a cap to fit to the leaking oil well. Malcolm Taylor: “They used their as-built drawings and all their information records. When they got down there on the first attempt they found it didn’t work, simply because they did not have the most up to date info about the design of [the wellhead]. If they had the correct info, they would have been able to cut off the leak much earlier.”
The Government is so-sold on BIM’s whole life cost crunching merits that in June it set up the BIM Task Group, headed by the Cabinet Office’s head of BIM implementation David Philp, to preach the good word. By 2016, all Government construction contracts over a certain value (today £5 million, but that may change) must be designed and built in a BIM environment. Crossrail will serve as a vast test case of the new normal.
Fast facts: Crossrail’s supply chain
A version of this article is featured in the November issue of The Manufacturer, out early November
