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BIM: Constructing a virtual world

In 2011 the UK government introduced a Building Information Modelling (BIM) mandate that hammered home the long-known inefficiencies in the UK construction industry.

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Remake, remodel: A BIM approach will be essential for future infrastructure projects

Traditional 2D-based design workflows are fragmented, prone to error and can put barriers in the way of design optimisation. By 2016 all public sector projects will need to achieve Level 2 BIM, delivering a fully co-ordinated BIM model as part of the process.

Eighteen months on and the construction industry is now robustly responding. At the second annual ICE BIM conference, in October 2012, 69% of delegates reported they were using BIM on a project, a significant increase from 2011.

BIM is now one of the hottest topics in infrastructure - not just for government projects, but also within the private sector, where firms are looking to reap the benefits gained by early adopters and remain competitive at home in the UK as well as on the international stage.

In the coming years a BIM process will be essential to be eligible to bid for new infrastructure projects in the UK, not only to drive efficiencies in the design phase, but pushing those benefits through to construction, operations and maintenance.

As a term, BIM is relatively new to infrastructure projects, but the technology-enabled business process that it describes is not. The benefits are already there to be seen as BIM for Infrastructure is being used to great effect on a number of key UK projects.

London’s M25 motorway widening project, completed on schedule in summer 2012, is a case in point. Through design coordination and careful construction planning, the Atkins, Skanska, Balfour Beatty joint venture finished construction in three years, approximately half the time it typically takes for a project of this scope.

“Autodesk BIM for Infrastructure solutions give us a more accurate engineering representation of the highway and a deeper understanding of the project during construction,” says Skanska Balfour Beatty engineer David Owens.

But is BIM really relevant to civil engineering? The ICE defines BIM as “the purposeful management of information through the whole life cycle of an infrastructure asset”.

And while its origins lie in buildings, the core principles and workflows associated with BIM apply equally to all infrastructure projects, including roads, railways, bridges, dams and water works.

“This model-based design approach means it is possible to spend more time evaluating different design alternatives”

A typical BIM for infrastructure workflow for road design illustrates this perfectly. A coordinated 3D model dynamically links all elements of the design. Move an alignment and the linked elements automatically update. The engineer can instantly see the impact on cut and fill volumes, while the BIM design tool automatically checks against local standards for speed, visibility, curvature and grades.

This model-based design approach means it is possible to spend more time evaluating different design alternatives to help reach an optimal solution. Forget about drawings made up from lines, arcs and circles: parametric wizard-based design tools make it easy to design complex roadway features such as junctions.

A structured BIM process also makes it easier to accommodate late stage design changes - edit the intelligent 3D BIM model and all the documentation, bills of materials and schedules will automatically update incorporating all the edits.

But BIM for infrastructure is so much more than “intelligent” 3D geometry. It can be used to optimise traffic flow, simulate noise, lighting, lines of sight, drainage, and signage. The virtual model can also be used downstream for construction planning and scheduling. The entire process can be simulated in full, helping improve constructability and remove costly errors before a project even goes to site.

Dutch firm Breijn used its BIM model for construction sequencing when designing a replacement railway bridge over the Linge River.

“ProRail [the Dutch railway authority] wanted a cost-effective replacement bridge, with minimal disruption of rail service during its construction,” recalls Brejin senior designer Cristian Otter.

“With the help of Autodesk BIM for Infrastructure solutions, we developed a design that met our client’s requirements for aesthetics, cost, and constructability.”

Breijn was given a tight 90 hour window for the bridge construction in which the rail service would be halted, the existing deck demolished, and new concrete decks placed on the bridge pillars.

“We created as-is infrastructure models and to-be design models to help coordinate our design and simulate the demolition and reconstruction of the bridge,” says Breijn construction engineer Leo Molenbroek.

“When we ran a 4D simulation of these critical 90 hours, there were still some pieces of the old bridge just hanging there. We had forgotten some demolishing tasks on the schedule. Thankfully we were able to find and fix these types of issues before they impacted construction.”

“As BIM workflows become more collaborative, with design and construction teams working closely, data co-ordination will be the next major challenge”

Construction planning also played a critical role in London’s M25 motorway widening project, with the existing road needing to remain operational throughout the three year construction period. At all times it was essential that three lanes of traffic in each direction were allowed to proceed.

The team used a virtual construction BIM model that incorporates detailed design elements, such as fences, crash barriers, and retaining walls, combined with point clouds from laser scans, and temporary works.

“This construction model makes the project easier to understand for all the on-site staff,” says Atkins senior group engineer Hugh Woods. “It informs their decisions for construction planning and helps them better understand their options when site conditions necessitate changes.”

BIM for infrastructure doesn’t need to stop in design, planning and construction scheduling. Highly accurate BIM models can be used to drive GPS-positioned excavators for automatic grading on site.

Workflows to monitor and record construction progress can also be implemented. Three dimensional laser scanning output, containing millions of points captured in seconds, provides the as-built data that can then be checked against the design model.

As BIM workflows become more collaborative, with design and construction teams working more closely together, data co-ordination will be the next major challenge. By centralising project information, the cloud is already helping ensure project participants have access to the most up-to-date data - at the right time in the right format.

Mobile devices, such as tablet pcs, are playing the increasingly important role of putting BIM-centric information into the hands of on-site construction professionals. To support a truly collaborative workflow, mobile devices can then be used to feed back information into a cloud-based virtual construction model, helping ensure construction schedules are kept up to date and budgets are controlled.

All over Europe there is a huge demand for new or updated infrastructure, but financial constraints have led governments to look at how they can get more for less. It’s here that BIM for infrastructure excels as it offers a planning methodology that can save time and money - all the way from design, through construction and into operations, optimising running costs throughout an asset’s lifecycle.

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