Digital dimension: A BIM model of utilities at Liverpool Street station
It’s a little-known fact, but engineers are actually building two versions of the Crossrail high-capacity railway link that, from 2018, will run east to west through the heart of London.
Most people are aware of the construction of the physical version, characterised by the tunnel-boring machines that are inching forward below the capital’s streets. But a second version – a virtual railway – is also being produced. Indeed, the entire project is being created in a digital format, which will enable future operators and maintainers of the railway to extract the physical, environmental and commercial data they need to do their jobs.
The creation of the virtual railway is arguably the most ambitious example of building information modelling (BIM) seen anywhere in the world – it has certainly never been attempted on a European transport infrastructure project of such scale before.
The use of BIM offers several potential benefits. One is the reduction of risk from greater visibility into design and construction interfaces. Another is a reduction in errors due to a ‘single source of truth’ approach to data management, which ensures that only the most appropriate versions of models, drawings and documentation are used. This latter aspect has big implications in terms of reducing costs and avoiding construction delays.
Malcolm Taylor (pictured), head of technical information at Crossrail, is BIM’s greatest advocate. “It is amazingly important for this project,” he says. “We are building a physical railway and a virtual railway. And it’s the latter that will allow us to run the former in perpetuity.”
Crossrail has been driving industry standards for design innovation on major infrastructure projects since the first surveying was undertaken in the mid-1990s. Detailed design work for the project began in 2008, and working in a collaborative 3D environment was a core contractual requirement across each of the 25 design contracts.
Today, Crossrail integrates the information developed from more than 25 main design contracts, 30 advanced works contracts, and more than 60 logistics and main works construction contracts, all of which have an extraordinary number of interfaces within London’s complex urban environment. Every contract produces some form of data – and Crossrail has sought to use BIM to manage the creation of that data and to make it meaningful.
Crucial to these activities has been the adoption of the single-source-of-truth approach to data. All contractors and designers on Crossrail are effectively made to work in one place. That’s not just a requirement for CAD activities – it also includes all documentation and spatial mapping. “The linked databases are the backbone of our BIM world,” says Taylor.
All the design to date follows a coordinated and consistent set of 3D rules and processes. To successfully manage the data, Crossrail chose to adopt a central software model for all 2D and 3D design files, using BIM.
So far, more than a million CAD files have been created, approved and integrated within the centralised information model. The 3D design information model is hosted by Crossrail and shared with construction contractors. And in the future, it will eventually move across to the operators and maintainers of the railway.
This centralisation, says Taylor, significantly reduces information loss between contracts and project phases. It decreases project risk by giving greater visibility into design and construction processes, and by using technology to make delivery more efficient and economical, as well as less disruptive. Having all the design models integrated into one centralised set of linked databases allows the Crossrail team to create detailed still and moving visualisations of specific elements of the project. Engineers can bring to life elements of the project well before work to construct them actually begins.
This approach allowed Crossrail’s engineers to be significantly more effective during the design and construction phases. It enabled the spatial relationships of all the component elements to be defined, thus ensuring that there were no clashes between, say, the mechanical engineers’ ductwork and the structural engineers’ concrete or steelwork.
Engineers were also able to visualise many of the complex utilities in and around the stations in 3D. This potential ensures that anyone working in the vicinity of the proposed stations is aware of the intricate weave of pipes and cables under the streets, which needs to be avoided or protected. Once each works package is completed, so in turn the CAD models are updated and reintegrated to the central database. This central facility can then be linked to other databases, allowing the visualisation of existing component elements alongside other data such as asset information and specifications.
Such an approach works only if all contractors and suppliers follow the same set of rules, particularly when it comes to data classification, coding and dictionaries. This requirement has led to the creation of ‘asset dictionary data definition documents’ – AD4s – which set out exactly what information Crossrail wants for each maintainable asset on the railway. This data is collected during construction and linked to operation and maintenance documentation, as well as to 3D models. Crossrail is working with Network Rail, HS2 and London Underground to try to achieve a standardised AD4 system, pointing towards a more collaborative future.
Getting contractors to work to a defined set of standards has been central to BIM, says Taylor. “One of the crucial things in terms of records and data is putting information into relational databases that can be sliced and diced and searched upon, linking the database of your records and information to your models and to your spatial world, so that you can move in and around these databases slickly and efficiently. But it needs specifications and standards to define what you want to do. So we have processes that people need to go through, and we explain exactly what we want.
“We have to do that. If we had one designer, one contractor, and one architect on Crossrail, my life would be easy. But we have six contractors, for example, all wanting to do their own thing. We have to bring it back to one specific standardised set of processes.”
To help it promote and manage this prescriptive approach, Crossrail has established a dedicated academy to provide hands-on training on BIM to the supply chain. The academy, based in London, gives Crossrail contractors focused learning on the latest software and best practices and processes used on the project. It offers the supply chain the advantage of working in a simulated Crossrail environment, so that they acquire detailed technical knowledge about the project processes and systems in a virtual world. Set up in partnership with software provider Bentley Systems, the academy offers a curriculum particular to Crossrail’s requirements.
This investment has proved fundamental in supporting the use of BIM and the successful imposition of a standardised approach to data generation, says Taylor. “At the simplest level, you have to set rules – whether you want to use inches or millimetres, pounds or kilograms, and so on. And so, for every asset, what we have done is to specify the information that is required.”
This standardised approach is not necessarily used by other organisations, he says. “That hasn’t always been the case in the UK. You will find that London Underground defines things differently from Network Rail, and even within organisations some departments might look at the same asset in different ways.
“But in our BIM world, where we want to get the information consistently right, the AD4s mean that all contractors on the project can look and see the exact information we require.”
Taylor is unapologetic about following such a prescriptive approach. “There needs to be a common data environment. As the enabler for BIM, it’s up to us to create that. It’s stipulated in our contracts, with our suppliers working in our electronic document and CAD management systems.”
That’s not to say that variations in file types cannot be handled. Bentley, for example, uses a file type called DGN, while AutoCAD uses a DWG format. “What’s important is that we can interchange the data,” says Taylor. “We recognise that in the mechanical plant field, in particular, there is fabrication software that can be hard to link to the types of models that we want. Where software is not directly compatible, we will work with contractors to get an end result.
“I have come across a lot of people who say that it’s impossible. But I haven’t come across a case yet that we haven’t been able to fix. We don’t compromise, but we help people get to a place that we know is achievable.”
Ultimately, Taylor wants all contractors on Crossrail to approach the creation of digital output with the same integrity as they would a physical product. But some companies cannot fathom the need to take such care when it comes to working in an integrated data environment, he says. “We can take a horse to water, but if it is not interested then there’s not a lot you can do.”
Fortunately, most contractors have bought into Crossrail’s approach to BIM. And with half of the project now constructed, an enormous amount of data has been amassed. At his office in London’s Canary Wharf, Taylor uses a laptop to dive into stations, moving freely around each location, highlighting particular assets and extracting data, models and documentation.
Strict on structure: Contractors and architects must stick to the rules on data presentation
This immersive environment has already proved invaluable during complicated construction sequences. At Tottenham Court Road, for instance, Crossrail tunnels were drilled to within just 860mm of the existing Northern Line. “That construction process went smoothly partly because the use of BIM visualisation meant we could easily explain to the interested parties the complex issues,” says Taylor.
And as the BIM model is built up, it will one day provide the operator of the railway with valuable information, thereby helping to lower lifecycle costs. “BIM data will help deliver improved predictive maintenance performance, meaning a more efficient railway,” he says.
Looking back at what’s been achieved through BIM so far, Taylor says it has helped to reduce costs in both design and construction, mainly through the reduction in error and rework because of the single source of truth. That decrease has fed into efforts to keep the project aligned to strict timescales, he says.
“We could have built Crossrail without BIM, as people have built tunnels and railways without it before. But it has made life much more efficient. Crossrail would be more expensive and higher-risk without BIM.”
Valuable lessons have, and are, being learnt, he adds. “We have had to become more prescriptive – and I never wanted to have to do that. I thought everyone would be collaborative. But some contractors haven’t acted quite in the spirit of our contract forms. It’s old-world thinking, which is a shame.
“All we can do is become more prescriptive. The more people battle against us, the more we turn round and say ‘well, actually, your contract says…’. But we don’t like having to do that.”
Government commits to BIM Level 2 adoption by 2016
Building information modelling (BIM) can improve performance on public sector infrastructure projects, reducing costs and delays, the government believes. So it has set up a task group to oversee BIM delivery. The aim is that, by 2016, all central government departments will adopt at least collaborative Level 2 BIM – the advancement of open shareable asset information through ‘file-based collaboration and library management’.
The adoption of BIM could result in capital expenditure savings of up to 20% on new infrastructure projects, with even greater savings across the lifecycle, the task group believes. It says that BIM-enabled working will allow geometry and asset information to be shared by different project participants and between different stages of design, construction and operation. An engineer would be able to use information sourced from the architect to prepare energy calculations, or check the coordination of contributions from different members of the project team. Programme and cost information could be captured. Most importantly, information about the use of the building could be held in formats accessible to facilities operators – enabling buildings and other assets to be used and maintained efficiently.
Engineering firms that expect to play a role in public sector construction projects need to get ready now. Firms might be involved directly, through engaging with a government department, or indirectly, with a supply chain partner that is engaged in this way and needs data as part of its contractual requirements. For more information on the government’s approach to BIM, visit bimtaskgroup.org.
Autodesk BIM software tackles complexities of cancer therapy unit
Autodesk has emerged as a leading provider of building information modelling (BIM) software, with packages such as Revit and AutoCAD Civil 3D being used for the planning, design, construction and management of new building and plant projects. The model-based software can be used to encourage collaboration through simulation and visualisation, with the aim of lowering construction and lifecycle costs.
Creative visualisation: Autodesk’s BIM can help to cut building costs
David Light, Autodesk’s expert on BIM in architecture, engineering and construction, says BIM can offer improved cradle-to-grave visibility. “The virtual models used in BIM can contain a lot of data. A client will come to us with a requirement for a building design, wanting to use that building over a certain amount of time, and to operate it in the most efficient way. That means understanding how it could be maintained through its lifecycle. By building a virtual mock-up, we can input a lot of data to that. It’s about models, but also about text-based data that can be extracted.”
One big construction project where BIM was used was the Scripps Proton Therapy Center, a $225-million facility in San Diego in the US, which will be able to treat around 2,400 cancer patients a year. In this case, designer Haskell Architects and Engineers wanted to use BIM to improve collaboration and coordination among the geographically dispersed team members.
At the rear of the Scripps facility is a 90-tonne cyclotron that creates a beam of accelerated protons that can target deeply buried tumours. To prevent unwanted radiation exposure, the team placed the cyclotron and associated equipment into a concrete ‘bunker’ with walls up to 4.88m thick. The adjoining, steel-framed clinical facility included treatment rooms, diagnostic tools, examination rooms, and offices.
Coordination between the two structures was challenging. Much of the building’s piping and electrical conduit had to pass through the bunker wall, necessitating careful planning. “All pipes had to follow a Z-shaped path through the wall,” says Frank Mangin, president of Haskell. “A misplaced pipe or conduit would be potentially catastrophic – and expensive.”
Because each structure behaves differently during a seismic event, the team also had to ensure that the criss-crossing mechanical, electrical, and plumbing (MEP) systems could accommodate different rates of movement.
Autodesk’s Revit MEP software helped to overcome these and other design challenges. For example, the main mechanical room was on the patient side of the facility. “We had to run piping underground, through thick concrete walls, and have it emerge in specific locations in the bunker area,” says Aryak Goswami, a mechanical engineer at Haskell on the project. “BIM helped us visualise how to place the pipes and conduit with high precision.”
Another challenge was coordination with the proton beam manufacturer. “Their equipment was custom-built, with precise tolerances – as little as one thousandth of an inch,” says Goswami. “Revit’s 3D modelling and visualisation helped us meet those tolerances and keep up with any changes that occurred during design – saving considerable coordination time.”
Once the digital model was complete, the design team walked through it virtually with the client, using Navisworks Manage. “We showed them what the completed facility would look like, checked for conflicts, and gathered feedback that helped improve the design,” says Goswami.
During construction, Navisworks proved valuable in completing the facility’s concrete wall, which required a sequence of pours. “The builder compared printouts of the 3D model with the pipes and conduits that were installed, verifying their accuracy before each pour,” says Mangin. This process helped the builder catch a missing pipe and correct it in time to avoid significant – and costly – consequences.