Columns, beams and braces.

For people using Revit Structure this post in going to be old news. However if you trained in Revit Architecture, this will probably be new information that can be very helpful. I’ve always had difficulty getting certain structural elements to do what I want so that they display nicely in elevations and sections. A recent project I worked on has slanted walls and with the slanted walls came a slanted seismic frame, slanted columns and a few braces. The pushed my use of the structural elements in Revit beyond the mere “post and beam” use that I blogged about in this post.

For this demonstration, I’m going to use my ‘Big Box Blog Store’ that I have been creating in past posts and add a new entrance with slanted walls and structure as a renovation. I’m also going to completely remove the concrete block wall along the elevation and replace it with storefront glazing and EIFS cladding. If you want a copy of the project file you can send me an email from the Contact page of this website.

Step #1 – Mass the new expansion

I don’t usually use the Massing elements in Revit, the type of projects I work on don’t usually require it. However, if you want to make slanted walls you will need to create masses. I like this approach however because if you change the mass Revit allows you to update you walls with a simple click. I won’t go into the details here because I’m focusing on the structural aspect. The screenshots below (Figure #1 and #2) show the massing I created and the walls created by using “Massing&Site->Model by Face->Wall”. The existing building is shown in grey.

Figure #1

Figure #1

Figure #2

Figure #2

 

Step #2 – Replacing the concrete block wall

The reason for replacing the concrete block with storefront and EIFS is it allows me to show you a typical verticle structure before doing the more complex slanted structure for the entrance and to show you a few Revit features that allow you to accurately place structural components.

Figure #3

Figure #3 to the right shows the structure I added to replace the concrete block wall in light grey. Nothing fancy but I wanted to show you the steps I took so that everything looked proper.

  1. If you want your columns to connect to the bottom of the beams, instead of the beam connecting to the side of the column, make the columns only partial height and then select the columns and use the “Attach Top/Base” command to attached the columns to the beam. If you allow the columns to be the same height as your beams when you add them to the model,  the beams will connect to the side of the column by default.
  2. If you beams cantilever past the column use the Start or End Extension values in the Properties Palette to adjust the length. This is easier and will give you more accuracy than trying to just draw the beam. There is also another reason for doing it this way in item #3 below.
  3. Since braces are usually connected to columns and\or beams, drawing braces is best done in a 3D view with the 3D snapping turned on (a checkbox appears in the tools option bar). With 3D snapping turned on the brace will automatically snap to structural items. In this project I was able to snap to the bottom of the column and then snap to the beam to make the K-braces. It doesn’t matter where you snap on the beam you can adjust the actual location in the Properties Palette after. In Figure #4 below I’ve highlighted the properties that control where the brace connects to the structural column\beam.
    Figure #4

    Figure #4

    The start attachment of this brace references a level because the start of the brace is connected to a column. I can change where the brace connects along the column by specifying a start attachment elevation.

    The end of the brace (end attachment) connects to a beam. The location on the beam can be controlled by either setting a distance from the start\end of the beam or by specifying a ratio (Eg. a ratio of 0.5 is 50% or the mid point of the beam). Note: the start\end point of the beam does not include the beam extensions I refer to in item 2 above, that is why it is better to use extensions to cantilever beams.

    The coping distance property only appears when a structural component has been coped. The Coping command is located in “Modify->Geometry->Cope”. The distance specifies how large the gap between the two elements should be. For the braces I used 0″ to make it obvious the braces connected to the columns and beams. I also had to increase the start\end extension distance to make the brace look connected. A structural component can be coped to more than one other structural components.

Step #3 – The Slanted Structure

Now that you know the typical verticle structure, the slanted structure will be easier. Figure #5 below shows the slanted structure in red with the entrance massing in transparent blue and the verticle structure in light grey. All other structure has been hidden from view.

 

Figure #5

Figure #5

  1. To make slanted columns; select “Structure->Column” on the ribbon bar then select “Modify|Place Structural Column->Placement->Slanted Column”. By default the first mouse click will locate the base of the column and the second click will locate the top of the column. Go to a section view of the column to set the angle of the column if you need to.
  2. Figure #6

    Figure #6

    For the horizontal beams spanning between the slanted columns, use 3D snapping and connect the beam at either the top or bottom of the columns. Next set the “Attachment Type” property of the beam to “Distance”, see Figure #6. Using this setting you can specify a distance from the top or bottom of the column and the beam will slide up the slanted columns. Also if you increase the angle of the slanted columns later on the beam will move with slanted columns. Note: the distance is measured vertically from the bottom of the column, not along the slant of the column.

  3. Braces should also be attached to the slanted columns using 3D snap, not the beams or they won’t align with the centreline of the slanted structure. Instead they will align straight vertically from the beam. Braces don’t have an “Attachment Type” property, see Figure #7 below. They only attach to levels but they slide up the slanted columns like the beams anyways.
Figure #7

Figure #7

A Few Last Notes

  1. Braces align to centreline of beams and columns in both the horizontal and verticle planes. I haven’t found a way to change this.
  2. When coping structural elements play around with the Coping Distance and Start\End Extension properties. If a coping distance of 0″ doesn’t get you the result you want, sometimes using 1\16″ will.
  3. Figure #8 below is what the final project looks like with EIFS walls and storefront added.
Figure #8

Figure #8

 

 

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Revit and Building Information Modeling