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.
Right Click over the family and select edit. You are now in the Family Editor. On the Home Ribbon click the Family Types command as shown below
In the Family Types Dialog box click the New Parameter command as shown below.
In the Parameter Properties Dialog click the Shared Parameter radio button and then select the Select button as shown below.
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.
Create the following formula. round(Length/Height)
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.
Next you create a project parameter for your Span to Depth Ratio. This will enable you to create a filter. On the Manage ribbon click the Project Parameter button as shown below.
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.
In the Filters tab click the Edit/New Button at the bottom of the dialog box. In the Filters Dialog box select the New command in the bottom left as shown in the image below.
In the Filter Name dialog box type Secondary Framing – Span/Depth OK.
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.
You now select the Add command to add your new filter into the Visibility/Graphic Overrides Dialog.
You can then add green to override the linework and for extra impact add a solid green shade to the members. Anything that displays green is now in the correct span to depth range.
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.
Hope you find this useful? I will try and create a tutorial video when I have some time.
LawrenceH
