Boolean operations in Revit

[ddarling]

Is there a Revit command similar to Interference (subtracting one parametric object from another) as it is used in ADT? At this time, I am using floor edit/sketch to create holes that accommodate the mass of structural columns that pierce the floors. Is there a better way?

[dhurtubise]

You can use join Geometry, that will cut your floor. Floor area will also be modified.

[kpaxton]

You can use join Geometry, that will cut your floor. Floor area will also be modified.Daniel,
That is one way to do that, but I dislike having to disagree with you. I think ddarling is wanting to see the structural column go through the slab.

I tried a simple experiment with a 50' x 50' - 12" floor slab and 6 structural concrete columns. Once placed, I used Join Geometry by selecting the column, then the slab - and the other way around - the slab, then the column. Both ways resulted in the column portion being removed from the slab (i.e. the slab being a contiguous piece). I did a Properties on the slab before and after, and both the volume (2,500 c.f.) and the area (2,500 s.f.) were the same!

If I understand ddarling, he's using the floor sketch itself to remove the unwanted piece of slab, correct? This is one way of providing for openings within the slab. Remember when you do this, you can Align/Lock the sketch lines for the openings to the edges of the columns. This way when you move the column or if it changes in size, it will change also automatically. Warning! If the sketch lines of your holes get close or near the edge of your slab, it will give you an error.

Another (similar) method is to use the Opening tool to create this hole. Used much the same way as in the floor sketch, select the "Pick a roof, floor, or ceiling and cut vertically" option, select the slab, then make your sketch. Remember to Align/Lock the sketch lines for the openings to the edges of the columns. I flexed the small column to different sizes and the opening flexed with it. You can see in the section, the difference in appearance - with the column now going through the slab. Note: This will not give you an error if you cross the edge of the slab!! - it will give you an error if you take the opening sketch totally outside the boundaries of the floor, as it has nothing to cut.

Both the Opening tool and interior Floor Sketch lines will 'remove' volume from the Slab (as reported by Properties). Join geometry appears to not remove this. What is everyone else's experience regarding this???

I was hoping there was a way to 'embed' an opening into a structural column family - and have it cut like a window or door, but the base family & Template do not include the 'Opening' tool (it's grayed out). You probably could also create a nested family, but I'm not sure if this would lose the special analytical aspects of a structural member. I suppose if you're just 'drawing' columns, you could make a generic member, but then you've also lost the structural nature of the element.

Kyle

[Steve_Stafford]

Join geometry will give you graphical joints between floor and column so it looks nice. If you really want holes in the floor give the Modelling menu > Opening > Shaft Opening tool a try. This feature will cut floors, roofs and ceiling it comes into contact for whatever height you specify.

So you could put one such shaft sketch on the lowest level, create boundaries around each column, specify how high the shaft opening should be, finish sketch. Works great for elevators and stair towers too. It is even a pretty effective way to manage the floor slab edge over many stories, if not a bit counterintuitive.

[ddarling]

Kyle, Daniel and Steve - thank you for your responses.

Daniel is correct, Join Geometry does not provide the result needed. The other suggestions appear to work. It is a shame Revit does not make this easier. With a large number of columns the process will be very time consuming, particularly if the shape is complex. Perhaps in later releases this can be improved.

[radu.grosu]

Yes, I also noticed that the Join command does not extract the appropriate volume from the object that is cut. It really should. And more (I write about this time and time again, it seems), some objects always cut the joined element regardless of the joining order. This is ruining my design intent and it's a shame.

[jwilhelm]

Revit does in fact provide a subtraction operation, you can create a void object the shape of the column and slightly thicker than the slab, and then us "cut geometry" and that will give you the hole.

[Steve_Stafford]

The Opening > Shaft feature does remove the volume from the floor that it alters, which is why I suggested it.

Using Join Geometry does remove volume from the objects involved, just not the floor. If you try this yourself, make a floor, make a structural column (concrete) and make sure they intersect each other. (assuming stock content)

Take a look at the properties of the floor and column before using join geometry. Use Join Geometry and look again and you'll find that the column shows less volume after the operation. The opposite of "your" expectations perhaps but a schedule for columns and one for floors will actually yield the "correct" volume just not how you might expect to find the values reported.

If I recall correctly the "intersection" boolean operation results in a completely new piece that represents how two or more solids intersect. Such an operation on a floor & column would result in a thin disc :smile:

[comhasse]

The Opening > ..Using Join Geometry does remove volume from the objects involved, just not the floor. If you try this yourself, make a floor, make a structural column (concrete) and make sure they intersect each other. (assuming stock content)...

:?: - very strange: i just did try this (Swiss German Template/Stock content) with a concrete slab and a concrete structural column. The exact opposite happens, the volume is subtracted from the slab, not the column. This is also displayed accordingly in a Section View through the Column when i switch to two distinct materials. I guess therefore there has to be a setting somewhere to set this hierarchy?

[Steve_Stafford]

That is interesting, I just tried it again with an imperial default.rte and the rectangular concrete column. Join geometry removed volume from the column not the floor slab.

[comhasse]

Just tried it again, this time with the default metric template. Same result as before - it doesn't seem to be in the template/families then. Also interesting: i can only join concrete columns with the floor, not steel columns (even if i switch the material to concrete). Btw. i am still working with Revit 9, so maybe hence the difference.