a severe watertight problem during meshing !! it kills me

[Anonymous]

i'm trying to model a reinforced concrete column, i draw the solid parts (stirrups and reinforcement parts) using autoCAD.

subtract them from the concrete encasement, and went on for meshing the encasement !!

sadly, the autodesk simulation keep telling me that i've got watertight problems !!

it took me about 3 hours to mesh this model (a crapy mesh very coarse), and about 6 hours to get a finer and within range mesh, and still, it's a watertight problem .!

am i missing ?! could anyone help for for the love of GOD 

[John_Holtz]

Hi 80106,

I have never worked with reinforced concrete, so I do not know exactly what your model looks like.

• Does it include the concrete AND reinforcing parts?
• What type of details are included in the model? (very small features in a very large column, etc?)
• What is the purpose of the analysis? Loads? etc.
• Is each reinforcing part (and/or the total of all parts) small in cross section compared to the cross section of the column?

Perhaps there is an alternative approach that would make the model easier to mesh. For example, if the rebars need to be included in the analysis, they do not need to be meshed as a solid part. Instead, one of these approaches may work for you:

1. Use the Nonlinear > MES analysis type and choose the concrete material model. This lets you define the properties of the concrete AND rebars using just one part.
2. Model the rebars using beam elements instead of modeling them as solids. Depending on what the overall model looks like, it may be possible and faster to make the mesh by hand. (I understand that it is not as fun as creating a cool 3D CAD model with every nook and cranny, but the objective of simulation is to get it done with the least amount of detail necessary, in my humble opinion.) 

[Anonymous]

THANK YOU JOHN:)

your responce is quick what i'm looking for 🙂

i'm attaching a photo from my model, i dont think the smerd model would solve my problem, the stirrups is a key component, thus, i need a full model to represent my -actual- physical model .!

i draw the geometry using autoCAD 2011, do you think it have anything to do with the watertight problem ?! do you have any recommendation ?! modeling via another software maybe ?! anything ?! i'm desperate 😞

[Anonymous]

BTW, those rebars and stirrups is sorrounded by concrete "hidden in the photo", as follow:

1. a box of concrete with the prober dimensions (3D solid)

2. copy the stirrups and rebars (3D solid) to the proper position

3. subtract those stirrups and rebars from the box to form the encasement

4. copy the stirrups and rebars again to the proper position

[John_Holtz]

80Dave,

Thanks for the image. (And thanks for attaching it instead of inserting it in the body of the post. Inserted images are often shown at a scaled down size on my computer (X%), so those images are usually unreadable.

My suspicion is that the water tight problems are occurring at the locations where the stirrups are tangent to the rebar. Considering that simulation is often accurate to 10% or worse (unless you do a full mesh convergence study, etc), the calculations probably would not be hurt if you either merge the stirrups and rebars, or add a "reasonable" gap between the stirrups and rebars. By merging them, I mean that the stirrups "interfer" with the rebar by something like 1/4 of the diameter, and then union them together so that they (stirrups and rebars) all become one part. By a reasonable gap, I am thinking something on the order of 6 mm or larger. (After all, the gap between the stirrups and rebars will be filled with concrete, so you don't want to create another problem by having too small of a gap.)

P.S. Sorry for calling you 80106 previously. I must have gotten that from another post.

[Anonymous]

john 🙂

i'm gonna consider the first option :), one part .!

the problem arise not in the rebars nor the stirrups, it's in the encasement "concrete" arround the fillets .! that's wt bugs me out.

i'm gonna do your first recommendation, and i hope it would work 😞

aaaaaaaand dont be sorry about 80106, it was me, by mistake i wrote this meaningless ID