I want to model CFM bearing walls in RAM modeler essentially for the purpose of creating a load run down to a podium level. My question involves openings in the walls.
My strategy is to create the walls using "other" and assign them as gravity. I will have several different types of openings to deal with. For example:
Door/Window headers
For these if they are small enough, I would like likely ignore them. However, if they are larger I may want to capture the effects of the point load on the transfer level. I don't believe you can put openings in gravity walls, so I'm thinking that I would just discontinue the wall and place a gravity beam between the two ends of the discontinued walls. Will this strategy give me a point load at the end of the beam applied to the podium level?
Discontinuous walls
Similar to the large opening, I will have cases where the walls stop and I will need a beam that extends from the end of the wall to some other wall. Again, will i get point loads at the ends of the beam?
Beams framing perpendicular to the walls
Some of the beams will frame perpendicular to the wall. I assume these will apply a point load at that location as well.
Is there a way for me to see the applied loads on the podium level as a result of this "load run down"?
Added question - Should the beams be cut back from the walls if importing them from a dxf?
Thanks!
I see, interesting. Thanks for following up. Not sure if I will have a good feel for the difference unless I try it both ways. Anyway, thanks again.
Sorry last question - is there a possibility of putting a column within a wall or would have two elements in the same location throw a modeling error?
For example, if there is a beam framing perpendicular to a CFM wall with a heavy reaction and the wall is long, RAM concept is going to see a long line load. However, in reality that is going to be a large, concentrated force. I could break the wall on each side of the column (say 1' from each side of the column) and add short beams to connect the column and walls. Then the column would bring this load straight down. However, could I instead just put the column in the wall and frame the beam in to the column?
We do things in Ram Concept that make sense for the analysis of concrete slabs supporting concrete walls. This is sometimes different than what we do inside Ram SS, and there is some variation in how lateral loads and gravity loads are treated, in fact.
Columns will only ever transfer a point load.
Maybe I am misunderstanding something. From the wiki it states:
"Point loads that are eccentric to the center of the wall will translate to moments and a non-uniform load at the base of the wall"
It then gives an example of what that would look like with a point load at the end of the wall.
Edit:Sorry I see that is what happens when it is imported into RAM Concept. Maybe I'm more confused now. Why would the loads not just import as line and point loads if that is how they are being brought down to the podium level?
If I used the column idea, would they import to RAM Concept as point loads?
Point load reactions on gravity walls are transferred straight down to the supporting structure when we are using tributary load analysis (e.g. Ram Steel, Ram Frame - gravity loads). It's only the Ram Concrete analysis that meshes the walls and thus distributes the point loads to the structure below.
So, using gravity walls for load takedown is usually fine. I see models with this setup frequently.
The idea of using lots of columns is also fine. It's harder to build that model, but possibly easier to track the forces.
Either way, some spot checking of total applied loads vs reactions (equilibrium) is a good idea.
Seth, Thanks for the response. Also Sorry, let me clarify a few things:
I plan to use the recommendation to place columns at the ends of the gravity walls, then draw the walls in RSS (sorry this was a large oversight in asking the question). However, I do plan to use the dxf file to import in the gravity beams where I want to place a "header" or "beam".
Having said that. Are there any issues with framing the beams into the walls as I have mentioned above as far as modelling goes?
After reading the wiki on modeling podium slabs I see that these point loads will not be transmitted down. Rather the wall is assumed to be rigid and will place an equivalent uniform load on the slab. My first thought is that this seems rather odd, but maybe there are good reasons for this. I'd be curious to know them if you don't mind. I'm just wondering if this is due to some engineering judgment or if it is due to programing / analyzing requirements.
I'm trying to decide if it is worth it to model the walls or just perform a manual load run down. And place the line/point loads on the slab.
This might be a crazy work around, but if you wanted things to transfer straight down, could you place steel columns, say 2' oc center as if they were wall studs and then frame gravity beams between all the columns? At the openings you would just space your columns to be at the ends of the openings (i.e. jamb studs).
Or can you put a gravity column inside a wall and frame your perpendicular beam into that column? maybe this would transfer the load straight down?