IFC and OpenBIM: what about infrastructure projects?

Posted on February 13, 2019 by Marie-Pierre Lebel
Category: Strategy

IFC and OpenBIM: what about infrastructure projects?

Too often, infrastructure is overlooked when it comes to BIM. The common misconception is that road or earthworks projects do not require multidisciplinary coordination. It is correct that many projects are realized with far fewer stakeholders than in a building, but the realities of information exchange between municipalities, engineering firms, and contractors remain the same. Redundant work from one project phase to the next creates a waste of time and information that could be avoided through the wider use of the BIM process.

There is more and more talk of CIM with regard to 3D modeling on a large scale (for example, at a city level). Applications such as Autodesk Infraworks or ESRI CityEngine have successfully linked built environment modeling to GIS databases in an increasingly efficient way, thus democratizing access to 3D models for site analysis purposes. The CityGML format has been developed particularly for this context and has become the most standard exchange format for modeling very large built environment areas. However, what about modeling at the design stage of an infrastructure project, on a smaller scale?

Collaborative BIM is still unknown in the field of infrastructure. One of the possible reasons for this is that BIM relies on the exchange of information among all project stakeholders, which underpins compatible and open exchange formats. However, in civil engineering design software (such as Autodesk Civil3D or Bentley InRoads for example), the widely recognized open exchange format is LandXML. This neutral format has not changed in its structure for several years, but to this day it remains the only intelligent format for the transfer of road alignments, survey points or earthworks between technological platforms of different manufacturers.

LandXML format import options in Autodesk Civil3D.
Figure 1.0 LandXML format import options in Autodesk Civil3D.

OpenBIM and neutral file formats

In the traditional, building-oriented field of BIM, the preferred neutral file format is obviously the Industry Foundation Class (IFC). However, the IFC format was not created to support civil engineering projects. This is why earthworks or engineering structures are generally categorized as IFCBUILDINGELEMENTPROXY, which often leads many BIM experts to believe that the models coming from Civil3D, for example, are "non-intelligent".

Intelligent IFC model export from Civil3D

It is quite possible to export intelligent IFC models from Autodesk Civil3D, for example, by including information on the dimensions or materials of underground pipelines, or on the lengths of curbs or sidewalks. Initial work is needed, however, to create the sets of properties required for coordination or quantity reporting, which I find this article covers well.

Once property sets are assigned to objects, you can export your terrain models, road corridors, and pipe networks using the IFCEXPORT command. Note, however, that you will need to move to a 3D view prior to export, as Civil3D will only export solid items visible on the screen (solids are not visible in plan view).

3D view of a model in the AutoCAD Civil3D interface.
Figure 2.0 3D view of a model in the AutoCAD Civil3D interface.

In summary, Civil3D models should not be seen as simple AutoCAD 3D models because of their DWG extension. You have to take the time to learn them in order to see their full possibilities.

Ultimately, coordination between all project stakeholders, at all stages from planning to execution, remains paramount to achieving an optimal project. Therefore, site templates are an integral part of a project's BIM process. In addition, pure infrastructure projects could benefit from lessons learned in the building sector.

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Marie-Pierre Lebel
Senior BIM Manager / Civil - CIM Technical manager

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