Structural Analysis In Revit

[Luciana]

Iwork for a structural engineering firm who specializes in residential wood framing design. We are considering Revit but need to know if it can intuitively calculate structural loading. In others words if we model a house will it tell us where to place beams & headers to support second floors and roofs and size these members as well? We would also like to be able to input various live and dead loads and have the sizing update accordingly. Can Revit perform these actions or are there any plug ins or software that can work within revit that will perform these actions? Thank you.

A recent change to the methodology of Revit structural analytical modelling has enabled new workflows and capabilities when representing the Revit design model. However, automation is now more relevant than ever, as the analytical model is not generated automatically while the physical model is being built.

The massive benefit of this new workflow is that engineers can now create early structural design models in Revit without having to worry about the actual physical members. For example, an early design of a building structure may need some columns and framing to support a floor. However, at an early stage the materials and geometry may not be known. As the design progresses, the analytical members can be associated with actual physical elements. This allows Revit to be used much earlier in the design process and, importantly, to reuse and develop the design model right to the completion and handover of the model.

When representing certain structural systems and configurations, the analytical model can easily be defined and edited and then associated with the physical element. A great example of this is when an in-place family has been used. Previous releases of Revit would not allow an analytical representation to be defined, however, you can now define an analytical model for in-place families which is useful for complex foundations.

In future releases we will hopefully see more Revit categories supporting an analytical model, an obvious addition would be the recently added bridge and infrastructure categories. It would also be useful to create panels from faade elements for wind loading.

In the image shown below, the Analyze ribbon is shown with the new member and panel tools to generate a structural analytical model that can be transferred to multiple design and analysis tools without having to invest time in modelling an actual physical structure.

Revit provides two types of analytical elements, a member and a panel. The members can be used for beams, columns, and braces. The panels would be used for wall, floors, foundation slabs and similar elements. Panels can also be curved which allows better interaction with the analysis software. It is a good idea to create a series of view filters to differentiate between the various elements. In the image below you can see simple frame with columns shown in magenta, beams in blue and bracing in yellow. This has been setup with simple view filters that colour each element based on the structural role.

Another new feature is the ability to show the section on each member, very similar to Robot structural analysis. This is simply enabled by switching on cross sections within the visibility/graphic overrides dialog.

The image below shows the model and results transferred back into Revit. Each load case and the various results can be plotted directly on the analytical model and presented in Revit along with other typical views.

So, in conclusion, Revit 2023 allows engineers to work with Revit at an earlier stage, define a flexible analytical model that is controlled by the engineer. The analytical model can be suitably simplified and has the potential to represent many more structural conditions than previous versions.

In this tutorial we shall look at a method of calculating and displaying the Span to Depth ratio for steel primary and secondary beams. In early scheme design of a steel structure many engineers like to use the span to depth ratio to size members assuming a uniform loading across the beam.

Revit can be used to calculate and display the Span to Depth Ratio by creating a shared parameter and making a simple formula. Typically, a span to depth ratio of 13-15 is used for primary beams and 18-20 for secondary beams. In the following tutorial I will edit a UB family, add a shared parameter and then use the value of this and the structural usage to activate certain colours with filters. The image below shows the filters colouring, green is OK, red is over the limit and yellow is under the limit. To follow this tutorial, you will need Revit 2016 or later.

The first step is to create a shared parameter, this needs to be shared as this may need to appear in a schedule or be taggable. On the Manage Ribbon click the Shared Parameters command as shown below.

If you already have a Shared Parameter file, then click the New Parameter command as shown below. If everything is inactive, then you will need to create a new parameter file by clicking the Create button.

You will then be presented with the Parameter Properties Dialog. I am naming the new parameter SDR (Span to Depth Ratio) but you can use something else if you prefer. You will need to ensure that the new parameter is created as a Number. Click OK to both dialog boxes. Your new Shared Parameter is now ready for use.

Next you edit a Universal Beam family (or other section type for non-UK members). In the Project Browser, open the families folder and browse to Structural Framing. Below I am adding the parameter to UB-Universal Beams, but you can add this to any Section you require.

Select your new SDR parameter and click OK. You now need to set the new parameter to Instance and group the parameter under Structural Analysis. Click OK. You should now see your new parameter in the Structural Analysis group.

This will take the length of the beam and divide this by the section height. Note that the section height appears under the Structural Section Geometry group. We then round this number to get a ratio value. Save your new family and repeat for other families where you want to calculate the span to depth ratio.

In the Project Parameter dialog, click the Add command. You will then see the Parameter Properties dialog as shown below. Configure the dialog by selecting Shared Parameter, select your SDR parameter and then click OK. Make sure that Instance is checked, group the parameter under Structural Analysis and check the category, Structural Framing. Click OK.

You now complete the last step to create a series of filters to colour the beams by their span to depth ratio. In this example you create a filter for secondary framing. You need to ensure that you have secondary framing in your project for testing. In a Project with the edited families that you have created in the steps above, open the Visibility/Graphics Override dialog and select the Filters Tab as shown below.

You can now set the Category, Structural Framing and then set the AND rules to the following. ADR is greater that or equal to 18 AND SDR is less than or equal to 20 AND Structural Usage equal Purlin. Note that the Structural Usage may have differing terminology depending on the regional settings and template applied. Click OK.

Once the filter has been set your secondary framing will appear green when the correct span to depth ratio is achieved. Note that you can create additional filters to show members that exceed and are too deep. You can also colour the SDR values in a structural framing schedule.

Quite often when structural engineers are viewing the analytical model within Autodesk Revit it can be a little difficult to see which members are fixed or pinned or have specific release conditions set. The standard way to achieve this is to select the analytical bar and then look in the Properties Palette for the information.

The filters are set within the Visibility/Graphic Overrides dialog box. In the example below, I have chosen to indicate a Fixed or Pinned condition by using the colours red and green. Note that I have also had to create a separate filter for columns.

I would suggest that you create a separate view within your current structural template to enable the engineers to easily check the release conditions on the analytical model, this is much easier that selecting each element and viewing the Properties.

Happy New Year and look forward to all the good things planned for 2017! A few Autodesk Revit Releases back (Revit Structure 2015), Autodesk made a change to the integration with Autodesk Robot Structural Analysis to allow the transfer of data via an Intermediate .smxx file (Structural Binary file for transfer). Whilst this new format offers some benefits, the older method did have a few additional features that have not been incorporated within the .smxx export.

Looking for a CAD tool to do structural load analysis. I like Rhino, and have looked at Karamba and Revit. Rhino inside Revit is an interesting direction. Is this to satisfy the Architectural base that uses Rhino?

I am unsure if BIM modeling can handle structural steel analysis well? what do Architectural engineers choose when money is no object to evaluate a steel structure with beams, joints and plates in all directions?

Thank you for that. I suspected this.

In looking at some of the Grasshopper plugins mentioned here I see FEA implemented but not joints. Concentrated loads through joints is a failure point that has to be modeled properly. I notice Idea Statica can link to Karumba, but what about Steel Connections (Robot Structural Analysis)? Is there a path to this through Revit? This seems to handle the connections, but I am not clear what analysis can be performed on a completed structure that is a mix of plate, stringers, beams and a few critical connections at main supports.

Correct about Revit, but that is the interesting part with rhino.inside.revit. use rhino and grasshopper to work with the geometry before going to any analysis package. Sometimes Revit can give grasshopper the right analytical model information, and some objects grasshopper will have to calculate itself.

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