Beam/Slab - Column Connection

[Anonymous]

I have a multi-story reinforced concrete building, i modeled the columns to have the following constraints, "Base Level = foundation level" , " Top level = roof level ", i draw beams at the perimeterof the floor  with continuous line and the slabs at the outer boundary of these columns & beams.

The first problem is when I check the column connection at the typical floor it shows the beams are stopped at the boundary of the columns, but the slabs are cutting the columns (which is incorrect).

The second problem is that when i tried to model the reinforcement of the column, the revit dealt with the column as one continuous column from base level to roof level, it didn't consider any parameters for the connections with slab/beam (which is incorrect too).

If there is any other correct way to modify these 2 problems, please clarify.

Thanks ..

[RDAOU · Accepted solution]

@Anonymous

Your observation is correct. But this is right behavior of Slab to Beam & columns... Slab will cut both the column and the beam; if you placed slab boundary at the outer perimeter of the beams then it has cutt off the beams as well with a thickness = to the slab...Go to the section and verify if you are ok with that.

Nonetheless; on your first problem (slab cutting beams); there are several ways to acheive this depending on which suits the purpose and user best

Option 1.

Instead of continuos line all around; edit the floor/slab boundary and trace it around colomns making cute at the outer perimeter and holes in the middle of the slab so coulmns pass through

Option 2:

1. Create a new or modify the existing column family by adding void.
2. Check/Mark "Cut with Voids When Loaded" in the family type properties
3. When you load the column family to the model; you use the default Cut tool from the ribbon>Modify:  select floor or slab first  then the column

Option 3:

Similar to the above (ie: cut with void) but using an separate floor hosted/based family which you can the load and place/lock on top of each column...But considering that you modeled the column from basement to roof one element!!! this option is useless

Option 4:

Unjoin Geometry...The slab will not cut the column but the additional piece of slab will remain casted in the column which is not ideal.

on your second problem (Column Reinforcement as one element); You modeled the column as one element; how would revit know or decide where to start and stop the reinforcement and when it should connect and to what it should connect? As far as Revit knows; you have a column 400x800mm and it is 30 meter high!!! You need to feed Revit the right info so that Revit does what you want it to do.

That being said and considering that you want the slab not to cut the columns because it is not correct; one understands that you want to model it the way you build it WHICH is a greate approach when one is thinking BIM...but then one has to ask, IS IT CORRECT to cast a column from basement to roof ie: is this how you would built it? When the answer is no you should understand why Revit cannot and does not do it on it's own

Personally I split the columns per floor; the way it is casted is the way I model it.

Step back for a moment and think...if things modeled the way they are actually built then if one uses "precast" elements instead of the normal cast in situ concrete..........then the slab shouldn't cut the column!!!!

If you try it 🙂 you'll find out that it doesn't cut the slab!!! so it is either 1 of 2;

1. Model the way thing are built in real life (split the beams and work by floor) then your frame will work the same way it does on site
2. Use one of the workarounds (Options) mentioned above.

[RDAOU]

PS: If you need help with any of the above options...all you have to do is just mention which and I can help you with a screencast

[Anonymous]

@RDAOU

Thanks for your detailed explination ..

I canceled the columns from base level to roof level & remodeled them splited at each level and it worked fine. Moreover,  when i model the column reinforcement using revit extensions, the revit deals with the column clear height not full height which result in incorrect stirrups distribution at the start and the end of the column, by other meaning the column stirrups should continue inside the slab/drop-panels and not to stop before or after the slab. I have considered column dowels at column top connection to ensure column reinforcement continuity with column above, this only workaround vertical bars, but it did not work for stirrups. (so if there is a way to fix this please clarify).

The other thing I do not know when i shoud use is colum attach, I know that column attach simply link the attached element to the column like foundation case, but should i use it with columns at each floor to attach it to slab/beam or not ? and if this affects the reinforcement connections in any way ?

Thanks ..

[RDAOU]

@Anonymous

I am not really sure how you are setting Revit Extensions up...best would be to sketch what you need or want to do and I can do a screencast showing you how to do it...wording sometimes can get confusing and guessing on one end wont really help anyone especially when it starts with one topic then end up with something else!!! However; I really can't explain it all on the forum...those are just basics and if you apply them your reinforcement will work with or without Revit 2016 Extensions.

You need to do your exercise and know at least all the basics and fundamentals then here on the forum you can fill in the gaps...like for instance Revit wont wait for you to join cencrete elements...I thought you knew that when using concrete elements; unlike steel and wood, they join automatically and revit does take that into account when you model the reinforcement ... See links HERE for more info 

• Also check this LINK HERE it explains the join order and which elements have dominance
• You need to go through this section too as well as the subsections related to it on Reinforcement (Rebars and Cover constraints as well as Stirrups)

LoL if all your posts are going to be like this; I think I will start avoiding them...Closing out 1 question of yours is starting to seem almost impossible (started with cutting out slab and splitting columns now we are into detailed reinforcement!!!

[Anonymous]

@RDAOU

Thanks for your reply..,

I attached a photo showing the column stirrups problem i have explained before, this case happens when i use revit extensions, may be it can be solved manually for each column type by adding additional stirrups inside the slab, (but in this case it will be waste of time ). Another reason for usin revit extension is that it considers concentrated stirrups zone at the start and the end of the columns, not equal stirrups spacing along the column as the normal method. (If there is any other way, please clarify).

To be clear, i have studied all fundamental and basic course, but non of them go through the details (specially concrete connections) iam trying to solve, besides i have checked the help pages you sent, but non of them gives clear example. 

I didn't jump to any other point through my question, but they are dependant in each other, i can not ask all of them at once, all of them are related to the beam/slab - column connection, either as concrete or reinforcement.

Thanks for your help, it means alot ..

[renanrr3]

The discussion about column modelling is something I have been having some doubts about, mainly for cast in-situ reinforced concrete.

Although in practice we build each column in each level separately, if I have one column that starts in the foundation level and go all the way to the top, in my project it is called lets say C1, i.e. Column 1, regardless the level I am working on. So, if I have a plan view of the Level 1, the Column 1 will be indicated there as C1, and if I have a plan view of the Roof Level, the Column 1 will be still indicated as C1. Usually we do not split the elements in each level, calling them differently and therefore interpreting them as different objects.

My point is, regardless the view I am in the project, the column that is continuous through the height is considered as one single object, even if in each level it has different reinforcement or even different sections. I do not know if that holds true for precast concrete projects, as I never design one, but it is so for cast in-site reinforced concrete.

And for what I have seem in Revit Structure, I can have a model that has such behaviour. If I have a column that go all the way through the height of the building, and I want it to have different section/reinforcement along the height, I have to model separate instances to account for this changes. But doing so, the column that originally I considered a single object in my project, now it is considered as two or more separate objects. And I could not call it C1 all along my project, since it is not reasonable to have two or more objects with the same name (Mark in Revit).

I know you can workaround it, perhaps attributing one suffix for each level (C1-lvl1, C1-lvl2, etc.), but it is not as straightforward as we use to do in the traditional way. In my opinion, if it is possible to implement this functionality (having one single instance of a column varying reinforcement and section attributes in its different parts) to Revit, it would be a huge step to create a more workable environment for structural engineers. But, if not, perhaps it is clever to adapt our traditional representation to this new tool, in the same way we have been doing with a lot of other things.

Best regards