BIM for Beginners: An Introduction to Building Information Modeling within Infrastructure Projects
Building information modeling (BIM) is not a specific software program. It is a streamlined process that allows us to make better decisions about project design based on reliable information analysis. BIM is an approach to the entire project life cycle, including design, construction, and facilities management. The BIM process supports the ability to coordinate, update, and share design data with team members across disciplines. It helps engineers better predict a project’s performance to increase safety, constructability, and sustainability before it is built, thus facilitating better decision making and more economic project delivery. In this article, I focus on three key benefits of working with BIM models which include:
- Data-rich models
- Reduced rework
- High-impact visuals
In an infrastructure project, BIM facilitates more design alternatives by spending more time during the project planning phase analyzing data rich models. The traditional, drafting-centric workflow makes evaluation of what-if scenarios inefficient and cost prohibitive. This is due to the disconnected processes of design, analysis, and documentation. Figure 1 diagrams the cost savings found through the ability to impact project performance earlier in the design workflow, when the cost of making design changes is low.
Figure 1: BIM workflow versus traditional workflow
Today’s infrastructure planners are expected to evaluate multiple design alternatives, recommend solutions, and help capture stakeholder buy-in before design begins. They do this with the help of geographic information system (GIS) professionals. GIS data is available from many different sources. Agencies around the world recognize the benefits of sharing information such as terrain data, parcel linework, soil data, land use information, wetland data and much more, as shown in Figure 2. Depending on where your project is located, you can find a lot of data online. Design teams need to be able to effectively aggregate and present the data in a way that is easily understood.
Figure 2: GIS data types aggregated together
Often, a 3D model is the easiest way to understand all the data and how it fits together. Many stakeholders and the general public definitely benefit from seeing the data inside a 3D model because they often do not understand 2D plan sets. Luckily, InfraWorks® 360 software provides a streamlined solution for gathering the initial site data while creating high-impact visuals. By taking advantage of Model Builder, design teams can quickly create a data-rich model by simply indicating where the project location is, as shown in Figure 3.
Figure 3: Model Builder
From this, a 3D model is created and stored in the cloud, which contains terrain data, aerial images, existing roadways, buildings, and water features. Additional data can be added as necessary using the Data Sources palette shown in Figure 4. Several different types of data can be added to the 3D model. The following is a partial list:
File Data Sources
- 3D model
- AutoCAD® Civil 3D® DWG
- Autodesk IMX
- Autodesk® Revit® RVT
- Bentley DGN
- Point Cloud
Database Data Sources
- Generic (includes OSGEO, OGR, Autodesk, etc.)
Figure 4: Data sources
If additional data is required for the project, make sure you download all the files associated with it. This ensures that you have everything you need. For example, if you find a shape file for your project, you must download the .dbf file to see the data behind the linework. It is also important to download the projection file (*.prj) so that the Autodesk InfraWorks 360, AutoCAD Civil 3D, and AutoCAD® Map 3D software all know how to automatically re-project the dataset into the project’s coordinate system. Figure 5 shows all the files associated with a floodplain dataset for Utah.
Figure 5: GIS dataset for floodplains in Utah
The best part of a BIM workflow is the reduction of costs correlated with the reduction of rework. The ideal project uses data created in early stages of the project design all the way through the design and construction process. Assuming you are following the workflow shown in Figure 6, let’s take a look at where data can be reused and what software is best to use for each task.
Figure 6: Typical infrastructure project workflow
I prefer to use Autodesk InfraWorks 360 for all the steps in the project planning phase. With Model Builder, you can define the project extents and establish the existing conditions in a matter of minutes. Then I use conceptual road tools to lay out several design options to provide to the client. Once they select the best conceptual design to move into preliminary design, then I create a new proposal based on that design.
If you have the Road Design, Bridge Design, and Drainage Design modules for Autodesk InfraWorks 360, then I would continue using InfraWorks for the preliminary design. Right-clicking on a conceptual road allows you to turn it into a design road, as shown in Figure 7. The benefit of doing this is that you can add design parameters to the roads such as curve type, curve radius, tangent lengths, and design speed. You can also have more control over the vertical design because you can view profile views of the design roads. Let’s not forget that you can also use cloud computers to calculate the optimal horizontal and vertical layouts of design roads. This is a priceless feature since you can run the calculation in the background while you continue working on other aspects of the design.
Figure 7: Conceptual road to design road
Once you have created and selected the preliminary design to move forward with, it is time to create the more detailed design. This involves taking the design from Autodesk’s InfraWorks 360 software into the AutoCAD Civil 3D software. Fortunately, the newer versions of software provide the capability to open an Autodesk InfraWorks 360 model in AutoCAD Civil 3D directly, saving a lot of rework.
In AutoCAD Civil 3D software, make any required adjustments to the alignments and profiles that came from the InfraWorks 360 software and design the typical cross-sections of the roads to create the finished ground contours. Finish up any other finite grading with grading objects and breaklines. If it is a sub-division project, lay out parcels. Last but not least, add annotation as necessary.
This is also a great time to move the design into Autodesk Navisworks® to perform clash detections to ensure that all the various disciplines parts line up properly. You have two options here:
- Export an .FBX file from InfraWorks 360 to import into Navisworks.
- Open the AutoCAD Civil 3D drawing file directly in Navisworks.
The benefit of taking the design from InfraWorks to Navisworks is that the textures and materials come across perfectly. The drawback is that every piece of the design is called mesh in the selection tree, making it more time consuming to hide specific items, as shown in Figure 8.
Figure 8: InfraWorks model inside Navisworks
When it comes to Design Communication, you use AutoCAD Civil 3D software to print the plan and profile sheets and either Autodesk InfraWorks 360 or 3ds Max to create renderings and animations.
To use 3ds Max, open the AutoCAD Civil 3D drawing. In the Output tab, Export panel, click Export to 3ds Max. To use Autodesk InfraWorks 360, create a new proposal using the master proposal as the base. Then connect to a data source and select Autodesk AutoCAD Civil 3D DWG in the file data types, as shown in Figure 9.
Figure 9: Add a data source to round trip back to InfraWorks
When the project is ready for construction, take the design back into Autodesk Navisworks. The Timeliner tool adds a fourth dimension by allowing you to connect tasks in the construction schedule with objects in the model. This creates a construction simulation, which automatically updates if the schedule changes.
Of course, any one of the models or all of the created models can be handed off to the facilities manager or government agency in charge of maintaining the new infrastructure once construction is complete. This saves time and money when resurfacing, remodeling, or rehabilitation needs to take place.
I hope this gives you a nice introduction on how to use a BIM workflow within infrastructure projects and makes moving to a BIM workflow easier for you. Until next time, happy modeling.