Adventures in time and space
Building Information Modelling is the technology everyone’s talking about. Jan-Carlos Kucharek reports on how a 4D BIM model is giving Vinci Construction UK additional coordination and control over the £560m contract to rebuild Tottenham Court Road station.
“Do you want to drive, or shall I?” We’re on site at Tottenham Court Road station where Vinci Construction UK’s senior engineer Lawrence Remmers has just asked the question of William Hackney, Vinci’s BIM strategy manager. Except we’re not in a car or a JCB, but their 4th floor site meeting room sitting in front of a laptop looking at Autodesk’s Navisworks Freedom — a 4D BIM viewer that allows team members to access the 3D design model linked to the “fourth dimension” of time management. Vinci is using it to help build this particularly complex example of city centre transport infrastructure.
On the screen is a complete virtual model of the site immediately outside their stacked temporary offices: the neighbouring buildings, the two huge holes in the ground, their props and retaining walls, the cranes, even diggers and trucks. Remmers, in charge of both the actual construction site and its BIM doppelganger, is navigating us around the view on screen. One second we’re looking at a bird’s eye view of the site, the next we’re hunkered in alongside the secant piles of the foundations, or at any point in between.
“Younger members of staff take to the programme immediately,” says Remmers. “It’s just like playing a computer game, except there’s no bad guys involved.” “Is that digger actually there?” I ask, pointing to a perfectly rendered image of one in the middle of the screen. “Well, it’s on site, although it may not be exactly in that position,” says Hackney. So the model isn’t quite rendering in real time, but as he’ll go on to explain, it’s not far off.
Taylor Woodrow, the civil engineering division of Vinci Construction UK, along with joint venture partner BAM Nuttall, is delivering the £560m, six-year contract to build the station boxes, connecting shafts, tunnels and fit-out for the new TCR underground and Crossrail stations. There was never any doubt among the Vinci team that BIM was going to be a core aspect of the procurement: the levels of coordination required between the consultant and construction teams made it a no-brainer.
Hackney heads Vinci’s dedicated BIM strategy team, which has been in existence for more than 10 years and works out of the company’s Watford HQ. This team dictates the BIM processes, platforms and tools that will be used on Vinci projects all over the country. Senior engineers like Remmers combine the roles of site manager and IT emissary, managing the engineering works and coordinating the 4D model.
With the huge number of consultants involved on the project, an “open BIM” strategy was adopted from the outset, with standardised IFC file formats allowing models that originated with the various consultants to “talk” to each other. Uniquely the client — London Underground Ltd — made the BIM data available during the tender period, improving the value in planning with the use of BIM.
“There is an empire of information being passed around between the teams and IFCs have facilitated that,” says Remmers. “Lead designer Halcrow has been designing in Bentley, and its native model has been issued to the station architects Hawkins Brown, the M&E guys and consultant Bailey Rail, who have been using it for their detailed design models. At the same time, all the temporary works and props have been designed by the sub-contractor [DAM Structures] in Tekla and exported to us in IFC format, while we’ve been using Autodesk AutoCAD to do our design drawings.”
As the construction side of the Vinci/BAM contract draws to a close, the main 4D BIM model will be passed to the fit-out team delivering the next stage.
Remmers says there were translation issues between Tekla and AutoCAD, but that IFC dealt with these issues instantly. Hackney adds: “The beauty of IFC has been that it hasn’t forced anyone to use the same software tools — it’s an enabling tool that has made the idea of ‘open BIM’ a reality.” The common data model is also supported by the use of the NEC3 Partnering contract, which places emphasis on collaboration rather than the traditional, more adversarial arrangements.
Of course, it is the 4D capabilities of BIM, the ability to link the design model to the programme and to examine the implications of design and programme changes, that makes it such a valuable tool on site. Vinci’s use of the Primavera P6 (Project Portfolio Management) to analyse the construction programme, and the use of Synchro project management software to look at “optioneering”, gives the BIM construction model a whole new level of functionality.
In the construction phase, Vinci found the system invaluable in its ability to be updated. When you are surveying as you excavate, or the programme changes, the model has to reflect the new conditions. “Ground modelling has been interesting for us as it is the one thing that no-one has a model for — we’ve had to carry out the surveys and create it for ourselves, including positions of existing utility service runs — and even the utilities usually don’t know where they run!” explains Remmers.
This “real” information obviously impacted on the virtual model, but as a result BIM allowed them to analyse the sequencing of site earthworks to optimise temporary works and prop deployment. This virtual placement of structures has allowed Vinci to “troubleshoot” the construction sequence before clashes ever become a problem.
“We would get Tekla models from the propping contractor, which we imported in to our Navisworks model,” says Remmers. “Being 4D, BIM allows us to see if there are conflicts with the propping sequencing and to deal with it before it becomes an issue, which has saved time and money.
“In one case here, we realised that we had a prop going right through a temporary shaft, and the model highlighted this, meaning we could design the shaft with a hole in it to allow the angled prop to go through it during the temporary works phase,” he recalls.
The Freedom viewer allows consultants and site staff to navigate around the virtual site and “interrogate” its elements
The real TCR site showing props for the station box dig and associated shafts
Remmers stresses that the model is “read only”, with Vinci assuming single-point responsibility for updating it. When events on site dictate that the model should be modified, he issues a “change order” to the technical team at Watford. “None of us can modify the model here on site. We need to limit the level of access to ensure that all changes to it are centralised — if everyone could go in and modify it, it would be a mess. Instead, the core team, in Watford or when visiting the site, do any necessary changes under my direction.”
Navisworks Freedom — the 4D BIM viewing interface — allows team members to access programme information as well as design data. Elements can be clicked on and interrogated to give details on installation and sequencing, or dimensional sizes of props or concrete volumes of retaining walls. Click on the purple-coloured “earth” element and it will tell you how many cubic metres of soil you’ll be excavating. As such, the construction team uses it a lot to visualise the site, check site levels and work out the logistics of concrete pours.
The Freedom model can thus be related to the variable of time and so can visualise how the TCR site should look on any particular date and the plant that will be on site. Which brings us back to that digger, and why it may not be in the position shown in the virtual model.
Will Hackney says that it’s about understanding fully the level of detail required from the model and balancing that against the cost of keeping it fully updated. “Granularity of this project model is weekly, and that works for us in this scenario,” says Hackney. “Real-time updating in construction is a matter for debate, although 4D is always moving towards greater levels of detail. We could keep it up to date constantly, but the labour intensity of doing that lowers the cost effectiveness of the tool. In terms of construction logistics in this case, it might be good to get to get the model updated on a daily basis to be aware of deliveries to site, but hour to hour here would be unnecessary.”
That said, both Hackney and Remmers mention a previous rail infrastructure project for the DLR where the nine-day possession to tie in the new grade separated structure at Canning Town was programmed and modelled along a critical path of half hours.
View of the site from the top of the Centre Point tower. The station box for the London underground station will be at the bottom centre of the image. The Crossrail box is being dug at the top left of the site
BIM allowed Vinci to see any conflicts with the propping sequencing and to deal with them before they became an issue
Similarly, Remmers discusses the interoperability of the virtual model with hand-held “palm” devices or tablets such as the iPad. “We don’t have it here, but I can imagine a scenario where it would be of value. On a job like this, where we are currently doing a big muck shift, we simply don’t need that level of functionality, but it’s an exciting prospect to think some time down the line an M&E engineer will be out on site and be able to refer to a wiring diagram on a manufacturer’s spec from a hand-held device.”
It also seems to be about keeping software up-to-date. Hackney says that his team of BIM experts at Vinci’s Watford HQ hold three versions of all the software used on site. “At any point in time we’ll have the old version, the current one and the beta version to help with forward planning and to ensure that the transition between versions is seamless,” he adds
And while all the bods in Watford are going to be au fait with all the software systems in use, at the coal face of the dig at TCR, the Freedom viewer is the user-friendly face of the technology revolution. “Training someone with the Freedom viewer takes about 10 or 15 minutes, so it hasn’t required significant investment of either time or money to use a tool that brings real project benefits,” says Remmers.
“On a day-to-day basis even screen grabs help us with method statements and activity plans. But more important, it means that even normal site operatives get the ability to connect the various aspects of the project and to visualise the target we’re trying to achieve.”
That’s part of the appeal of BIM — its ability to work on the most general level to that of the smallest technical detail. And the real skill, according to Hackney, is in controlling the information to ensure it’s optimised for the project in hand; which, one assumes, is where he comes in. “With BIM too much asset information can be overwhelming, so you need to know your audience and have to strip some away to keep the model legible,” he says. “What is of most value for you to see at a particular point in the project? Good BIM practice is all about tailoring the information to the viewer.”