How to Create a Spiral Beam

by GRAPHISOFT and lnagy · updated: 08.21.2012

As we know a spiral is a space curve with a consistent arc and a consistent inclination angle at all points. ArchiCAD’s Beam Tool does not have a curved option. Therefore any curve in the Beam must be created out of straight segments. However, it can be inclined buti t can consist of only straight segments. So a possible option is to construct a spiral Beam out of a series of inclined Beam pieces. Here is how to do it.

Version 1 – By Using Inclined Beam segments

  • 1. Draw the circle or arc of the Spiral.


  • 2. Decide on the resolution of the arc of the Spiral. Consider the size and full length of the arc. In our case let us create a full circle out of 32 segments. Let us draw the segments for the arc/circle.



  • 3. Draw an inclined Beam segment along the circumference of the arc/circle between two division points.


  • 4.Go to the 3D Window and increase the inclination of the Beam so it is the desired value. For example, if the total inclination of the Spiral is 4800 millimeters, then one segment will incline 150 millimeters.

Hint: You might want to set your Working Unit to the highest possible value for best accuracy during input.


  • 5. Go back to the Floor Plan, select the Beam segment and use the Multiply command with the Rotate option. The vertical displacement should be the inclination of one segment since we want the segments to join properly in the Z direction.



  • 6.Go to the 3D Window to see the result.


  • 7. Notice one thing however: if you zoom in very close to a point where to Beam segments join you will see that the join is not perfect. For them to be perfect the Beam would have to have the ability to have a distorted section, which it does not.

So this is a limitation therefore you should set the resolution to a large enough value so these errors are within tolerance.


Version 2 – By Using the “Curved Ramp” Object

There is another way to create a spiral Beam and it is even better since it does not have the disadvantage just mentioned. This unconventional solution uses the Curved Ramp object that is part of the default ArchiCAD library.

  • 1. Go to the Object Settings Dialog and using the search functions find the Curved Ramp object in the ArchiCAD Library.
  • 2.Make sure the “Side Flange 1” and Side Flange 2” parameters are turned OFF.


  • 3.Under the Ramp parameter group there are some parameters we need to set. Let us set “5800” (millimeters) for the “Smaller radius” parameter and “200” for the “Full width” parameter. Let us set “360” for the “Angle” parameter so it goes a full circle.


Note: The “Bigger Radius” parameter is affected by changes in the values of both the “Smaller radius” and the “ Full width” parameters, so you should set the latter two and the value of the third will change accordingly.

  • 4. Set the Ascent Length value to the full z value the Beam inclines. In our example this is “4800” millimeters. Also set the “Thickness” parameter which is “200” millimeters.


  • 5. You may want to play around with the 2D Representation parameters since it will display information related to the Ramp you might not need. You can, for example, decrease the size of the Text parameters to “0.0001” (practically invisible) and set the Text and Arrow pens to a white color.


  • 6. Click OK to accept these changes, then click the center of the circle to place the Ramp. Then delete the circle as it is not needed anymore.


  • 7.Check out the result in 3D.


What is even better is that since the Ramp is a GDL object, it uses GDL commands that make it possible for it to be created out of one entity. Therefore the segments join correctly as it is possible to do in GDL.


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