Making Construction Possible: How VDC Has Become an Indispensable Part of the Rail Consultant’s Toolkit

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Virtual Design and Construction (VDC) has come to define construction planning and has become an integral part of rail infrastructure planning.

Demand for virtual design and construction (VDC) is growing at the early design stage of large and complex rail infrastructure projects. Its application can help projects run to schedule and limit the need for costly re-work. VDC has earned its status as an integral part of rail infrastructure planning in the UK and it allows consultants to carefully manage otherwise unmanageable variables that occur in the interim phase between design and construction.

VDC and BIM defined

Contractors in the construction industry have been using VDC for around 20 years, using it to create realistic computer-generated models to show how a project can fit together. While non-engineers may be forgiven for confusing it with building information modelling (BIM) – which focuses on advanced computer-aided design (CAD) models to provide detailed information of various components of an asset – the two disciplines are quite different.

For example, a VDC model of a proposed station redevelopment can present a visually clear presentation of, say, a clash detection issue that needs to be addressed before a project can go ahead. And it can do so in a way that non-rail infrastructure engineers can understand, thus enabling closer client and stakeholder relations. Indeed, every activity that is required to build a project can be presented in a totally accurate, 3D, 4D, or 5D virtual environment – i.e., one that includes height, width, depth, time, and cost dimensions and enables clear visualisation of a construction programme as an animated sequence – before a spade breaks the ground.

However, and as its name suggests, VDC doesn’t stop with a model. Its strength isn’t just in providing complex, detailed modelling, but in providing design optioneering1 solutions that effectively enable construction to go ahead. The value of bringing VDC in at the early design stage of a project is certainly not lost on clients; through the detailed analysis of the entire life-cycle of a project, from its design to its construction, project schedules and costs can be reduced and productivity boosted.

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In the last ten years or so, VDC has shifted from being a solely contractor-based skill to one increasingly employed by engineering consultants during the early design stage of a project. Many VDC consultants – myself and most of my team included – have a contractor background. Clearly, a profound understanding of the construction process and constructability is highly advantageous during the critical option selection and the early consultant-led design phase where various design options and their repercussions on, for example, track layout or functionality, are considered.

It is at the early stages of a project where changes have the least implications on cost and programme schedule, and where they can create the greatest overall benefits in the long-term. Accordingly, changes made at the later stages of the project cycle have higher cost implications. Therefore, employing VDC techniques early means projects can move forward with greater certainty and reduced risk to clients.

Creating an interim world

Early design work usually focuses on the end state of the infrastructure and is based on existing layout operations and survey information to provide a design vision. Early option development and selection will also focus on this end state, but against a set of client or project requirements that must be achieved to release the project’s benefits and present the desired business case – this could be anything from the overall cost and duration of the project to the disruption it will cause to the existing service while construction is underway.

VDC allows the entire early design work to be ‘staged’ from its current state to its end state (see Figures 1 and 2). In this way, it provides the final design vision well in advance of the detailed design stage, creating an interim world that supports the permanent design – which could be a finished rail station – and reduces the number of temporary works needed to get there, which could include road closures, the use of tower cranes (see Figure 3), or cable route diversions, for instance. This detailed, interim world provides clients, stakeholders, and designers with a clear, visual indication of what is required to make the project meet their requirements and effectively removes any nasty surprises along the way, which could come in the shape of additional land take2 or other additional works that may be required.

Figure 1 – London Bridge Station Visualization – Stage 1 – Arch Demolition

Figure 2 – London Bridge Station Visualization – Stage 1 – Piling & Substructure

Given the implications of long-term rail projects on a growing swell of passengers, it is understandable that clients are now defining ‘interim / staging’ requirements for passenger service to minimise disruption to key operational periods, which the project must deliver against. This is where contractor experience brings higher value, supporting the theoretical ‘interim’ design with the real world experience of constructing a project.  It is in these interim stages where project delivery feasibility lives or dies.

Figure 3 – London Bridge Station Visualization – Tower Crane Working Area

Keeping things moving, safely, on the London Bridge Station project

WSP | Parsons Brinckerhoff’s role in the redevelopment of London Bridge Station (Thameslink Programme Key Output 2)3 has been comprehensive and varied throughout the development of this transformative project, from the early design feasibility and optioneering stage that began in 2008, to now, where we continue to support the contractor at the detailed design stage as Lead Station Designer. We have provided the electrical track equipment and track remodelling designs that will make KO2 a reality, and a complex staging process that will deliver a re-designed station with a theoretical throughput of 24 trains per hour.  Figures 4, 5 and 6 show various views of London Bridge Station during stage 1 of construction.

Figure 4 – London Bridge Station at Stage 1 of Construction

Figure 5 – London Bridge Station at Stage 1 of Construction

VDC was used in the early development of various construction strategies across the programme of works enabling us to optimise the station design with the development sequence and the construction of the track, and integrating it with construction sequences on other related projects to reduce costs and schedule duration, and deliver a fully integrated programme.

The project is now in the third year of a five-year construction programme, and our construction strategy has remained unchanged. This is in no small part a result of the early implementation of VDC and the experience of the team who created the interim world.

Figure 6 – London Bridge Station at Stage 1 of Construction

Working with pedestrian modelling specialists and the station management team, we used VDC on the London Bridge project to examine staging options to see how construction will affect passenger movement around stations. It allowed us to identify unsafe passenger flows and pinch points that could lead to platform or concourse overcrowding and, consequently, costly temporary closures.

An early integrated approach to pedestrian modelling  allowed us to explore options for adjusting the operating schedule, the stopping patterns, and train dwell times, and to provide an optimised construction programme that features, for example, ‘non-stopping’ platforms that could remove the need to create space for passengers where work is taking place. Through strategically integrating these elements, we developed a train operations plan, including key pedestrian flows and construction sequencing for the station and the railway systems design.


A bright future

WSP | Parsons Brinckerhoff has been using VDC for many years on infrastructure projects in the US, such as the San Francisco-Oakland Bay Bridge where 3D-computer models revealed various design alternatives, and for the Metropolitan Transportation Authority in New York, where we are designing the East Side Access project for Long Island Rail Road passengers and using VDC to provide accurate 4D clash detection.

Although comparatively later, the UK has embraced VDC to define the early design phases for major rail projects and it is now viewed as a core rail infrastructure engineering discipline alongside more traditional skills and design disciplines like track, signalling, and overhead line engineering. Tellingly, it is also a common client expectation for UK project teams to have a sub-team of VDC and constructability experts at their disposal.

VDC has been increasingly used in our work with Network Rail and organisations such as Transport for London, HS2, and Transport for Greater Manchester, as well as the train operating companies (TOCs), developers of rail freight facilities, and myriad contractors engaged in the implementation of rail projects.  Indeed, WSP | Parsons Brinckerhoff’s VDC team has grown considerably in the last three years and continues to expand.  Although the benefit of VDC is quite literally clear to see, it is the team’s ability to understand the projects and their various requirements that enhances its manifold benefits.

1Optioneering - etymology: option + 'eering' [from engineering] hence "to engineer (fig.) an option; to consider, in depth, various options and then to advise as to the best option." A term increasingly used in industry when management needs to be confident of a course of action; particularly where regulatory or funding bodies seek a demonstration of due process.

2The area of land that is 'taken' by infrastructure itself and other facilities that necessarily go along with the infrastructure, such as  railway stations.

3Thameslink Programme construction is divided into three stages, each with 'key outputs'. Key Output 0 was to make service changes to allow other work to proceed. Key Output 1 was for work that had to be completed before the 2012 Olympics. Work for Key Output 2 started after the London Olympics, with a planned completion date of summer 2019.

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