RAM Revit Link Best Practices

⇑ Up to the RAM Structural System Revit Link

Please read the Disclaimer.

Introduction

The Bentley RAM Revit Link can be used to export Revit Structure models to the RAM Structural System. Or, you can start in RAM Structural System create your model and import it into Revit Structure.

Starting in Revit Structure

When the model is started in Revit Structure there a few things to consider for a successful export to RAM Structural System. The most important thing to remember is not to model something you cannot model in RAM and expect it to successfully export from Revit.

When modeling your building in Revit Structure, you will need to follow a few best practices to ensure a successful export to RAM Structural System. 

Ground Level

The Bentley RAM Revit Link now has coordinate mapping so that you can model structures in Revit below the ground floor. When you export to RAM the lowest level in the RAM model will be at the 0’-0” elevation. (See the Wiki article on  Coordinate Mapping)

Levels

Be sure to set the Base Level and Top Level appropriately for columns and the Base Constraint and Top Constraint for walls as shown below. (See Figure 2 below.) The top and bottom levels should always be set to the closest level. You should never offset from a level which crosses another level. If you build the model so that all of the analytical lines are at the deck bearing level your model will export successfully.  If you have depressed framing on a level set them members to the deck bearing level and offset them in the Revit Element Properties dialog. If the analytical lines do not intersect in Revit the members will be unsupported in RAM. (See Figure 1 below.)

Figure 1: Analytical lines set to the top of steel level.

Figure 2: Set Base and Top Level to correct reference levels

Vertical Braces

For vertical braces, be sure to set the Reference Level to the top level to which the brace attaches.  Otherwise, the braces will not export correctly to RAM Structural System.  (See Figure 3)

Figure 3: Vertical Brace Reference Level

Foundations

Add the foundations to the model at the same level as the bottom of the column. (As shown in Figure 4) On export, the link will determine which member a foundation supports and will associate the foundation with the same level as that member in the RAM Structural System.

Figure 4: Footing modeled at same level as supported column

It is important to Analytical Model Tools in Revit to detect any modeling errors before exporting to RAM. On the Analyze tab run Consistency Checks and Check Supports. Address any errors reported before exporting.

As you build your Revit model make sure that the elements you add have the properties set correctly. This can prevent having to make changes later.

Analyze As

Revit Structure provides this property for beams, columns, and braces.  Braces will always be exported to RAM Structural System as lateral members.  To export beams and columns as Lateral members, be sure to set the “Analyze As” flag accordingly. It is a good practice to only export the objects that you want analyzed in RAM Structural System. You can do this by creating a selection set of the objects in Revit. Or, you can set the “Analyze As” option to “Not for analysis”.  

Figure 5: Beam with “Analyze As” flag set to Lateral

For the Revit Link to detect cantilever framing conditions you need to set the check Member Supports in the Structural Settings dialog.  (See example below).

Figure 6: Modeling cantilevers for export.

To ensure that loads are exported to RAM as expected, please note that Revit Structure load nature names are mapped to the RAM Structural System load types as follows:

¹ RAM SS can only handle one dead load case so all Revit Structure dead loads are added together if more than one occurs.

² These are not default load natures but can be added within Revit.

Note: Load nature names, which are editable in Revit Structure, must match exactly as listed above to ensure proper mapping between systems.

Once the building is modeled in Revit Structure and has been saved, you can export the model to RAM Structural System.  On the Add-Ins tab in Revit Structure, select External Tools > Export Model to RAM.  This will launch the RAM File Exporter dialog.

Figure 7: RAM File Exporter dialog

Export Options

The default location for the new RAM model is the same directory as the Revit model, and the default name is the same as the Revit model name. 

You can optionally export only members that were first selected in Revit Structure.  As mentioned earlier you can set up selection sets and pre-select the objects before opening the export dialog.  If you do export only selected objects do not use the Perform Deletes options in either the import or export dialogs. This will cause your non-selected elements to be deleted when you update.

Click the Settings button to see additional export options.

Figure 8.  Export Settings

To maintain the element shape type when exporting to RAM select Freeze Gravity and Lateral member. You can clear the design once you are in RAM so that it can design the members.

By default, the exporter will launch the new model in RAM Structural System when it is completed.  Select None to simply create the RAM model without launching RAM Structural System.

If your Revit model is not modeled at 0, 0, 0 origin select the Offset tab to enter the coordinates. The RAM model will be created at the 0, 0, 0 origin. The offset will be stored in the RAM model and used to update the Revit model correctly. (See the Coordinate Mapping article on the RAM-Revit Link Wiki.)

On the Other tab default option for log messages is to log the minimum number of messages.  This option will report any errors on export.  For the most information on the export process, select the All option for Log File Messages.  The All option is especially useful for diagnosing problems. The log is not automatically saved and you will have to save it if you want a record.

Mapping File

The RAM Structural System link to Revit Structure makes use of a mapping file to map Revit Structure Family files to the corresponding shapes in RAM Structural System.  The default mappings should work in most cases.  However, if you use custom families in Revit, you may need to modify the mapping file.  Click on the Edit button to launch the mapping file dialog.

Figure 9: Dialog to edit mapping of Revit families to RAM shapes

Note that the Revit Link comes with separate Imperial and Metric files.  To change the Revit family associated with a RAM Shape, simply double-click on the Revit Family Name and a File Open dialog will appear where you can select a different Revit Family File. (See the Revit Link Wiki page for the Enhanced Deck Mapping article.)

Exporting

Once the export options have been selected and the mapping file is set up correctly, click Export to begin exporting the model to the RAM Structural System. 

This section covers what you need to do in RAM Structural System before importing your RAM model into Revit Structure.  It assumes familiarity with the RAM Structural System.  In order to maximize the benefit of the link with RAM Structural System, there are a few practices we recommend using when modeling in RAM and importing to Revit Structure.

There are few modeling restrictions for building your RAM Structural System model for import into Revit Structure. There are a few guidelines to follow and there are some limitations to what you can model in RAM.

Gridlines

Each grid system that you create in your RAM model must have unique grid labels. If not when you import the RAM model duplicate grids labels will be automatically relabeled as they are created. This includes unlabelled grid lines in RAM. Revit considers unlabelled grids to be duplicates and will rename them each time they are imported. This does not apply to construction grids. They are not imported into Revit.

Levels

You should not use level names that are used in your Revit template file that you use when importing the RAM model. If the names are the same you should change them in the new Revit project file before you import.

Columns

Presently when you model columns in RAM they are imported as individual columns that can only extent from one level to the next. Multistory columns cannot be imported into Revit. If you modify the columns in Revit so that they are multistory, they will maintain the multistory length when updating from RAM.

You can import your RAM model at any stage of design. All of the gravity and lateral members must have a size assigned or the import will log an error.  

Project Template

When importing a new RAM model into Revit, you should always start your new Revit project from a template.  Although this adds some levels that you do not need in the model, the link does not work well if the Revit project is started without a template. Your template should include members from each type of family you will be importing from RAM. It does not need to have the exact size loaded into the template but it works best if there is a member of the family loaded. This is especially true for concrete members. If you have both square and rectangular concrete columns in your RAM model you will need to have one size from each of the Revit concrete column families loaded into the template.

Delete Levels

Once the RAM model is imported, the default levels from the project template (Level 1 and Level 2) should be removed from the model, especially if the model is to be re-exported to the RAM model at a later time. 

Here is a list of a few limitations for importing your RAM model.

• Continuous foundations are not imported.  (This is a limitation of the Revit Structure API.)
• Pile cap foundations are not imported.
• Grid bubbles may not be at the same end of the grid lines as they are in RAM.
• Grid lines may only show up on lowest level imported. (The easiest way to get the grid lines visible on all levels is to cut sections across the building perpendicular to the grids. Open the section views and stretch the vertical grids to the top of the building.)
• Load combinations are not imported.

What is imported?

• Steel beams, columns and braces.
• Concrete beams, columns, walls and isolated foundations.
• ‘Other’ walls. (imported as Generic)
• Member end fixity.
• Material properties.
• Column orientation.
• Beam camber (in inches) and stud information.
• Maximum beam reactions.
• Gravity point, line and surface loads.  *

* These items are only imported when importing a new model from RAM, not when updating an existing Revit model.