Solidworks FEA

[kaffy]

Good morning fellow engineers,
I am working on a linear static analysis of a part(as shown in attached pdf) which is attached to concrete wall with 8 hilti anchor bolts. I am trying to find out the shear and tensile load acting on the anchor bolt due to load(as shown in pdf). When I use the foundation bolt, then the results I got on shear and axial load is shown on the attached pdf which is definitely incorrect. I am trying to understand what am I doing wrong.
I could use the other approach where I create a split surface to represent the washer and then set a fixed face constraint on that and eventually find the reaction load on that fixed face. But then I run into problems of stress singularities during mesh refinement. Also when the option of foundation bolt is there, there should be no need of alternate approach.

Thank You
KD

 

[FEA way]

Have you tried modeling a small part of the wall to which this structure is attached ? Maybe a simplified solid model of the bolts (without the threads of course) could also help but bolt connectors should work too.

 

[NRP99]

I don't use solidworks FEA. So these are my general comments.
The second approach looks fine for me. And stress singularities may be problem for the result presentation, it may not be a problem for force calculation. Try mesh convergence study with 2-4 mesh sizes or elastic-plastic model and then conclude that the stress is not going to be as high as shown by analysis.

IMO, it will be easy to find out the forces using analytical formulae.

 

[rb1957]

I don't know SW either. "foundation bolt" is a 6 dof constraint ?

I imagine you have 3D elements for the brkt, why not !?
so at the support I'd have an RBE spider (joining all the nodes on the bore of each hole to a central node) This node I'd add 3 finite stiffness constraints (three translation directions) ... many ways to do this (I like to use 3 rods, each to a hard constraint). The stiffness value is not really important, something like 1E6 to 1E4.

If you want the added complexity, constrain the lower edge (as it bears against the concrete).

another day in paradise, or is paradise one day closer ?

 

[FEA way]

Internally bolt connectors in SolidWorks Simulation are just typical beams connected with (usually) rigid elements to the structure.

Since the 2020 version, it's possible to select the distributed coupling instead of a rigid connection. Maybe it could give you better results if you don't use it now.

 

[kaffy]

@FEA way.. Sorry I am not sure how modeling the wall and bolt helps. Do u mean: Model the bolt, nut, washer then create a split surface around the cylindrical surface of bolt and then fix constraint on it?

 

[kaffy]

@NRPP, So I use the split surface, run FEA and then find the resultant axial / shear force on split face(which wont change on mesh refinement as singularity is on the corner, not exactly on face).Right?

 

[FEA way]

What I meant is that when the simplified model of the joint doesn't give you the expected results (although it probably will if you change some settings) then you can try another level of simplification and model most parts as solids. It's a quite common approach that the bolt is represented by a 3D geometry without the thread (simplified nut and washer can be included too). Modeling part of the wall will let you account for more complex interactions within this connection. But that's a last resort and I would try fixing the issue with bolt connectors first.

 

[kaffy]

@RB1957, Yes it is actually an anchor bolt, So u drill a hole in the wall and then put the bolt in. After u tighten it to torque, the rear portion expands(as shown in video) and then it cant come out and constraint all 6 degrees of freedom.

https://www.youtube.com/watch?v=_Q9PBJGwggM

(for reference)


Solid works simulation creates the mesh by itself and yes it is 3d element.

So your method involves manual creation of mesh and then u are setting the constraints on a center of those nodes.. Is that right? I do not think I can manually create mesh (nodes) in sold works simulations

 

[kaffy]

@FEA So the way internal connector works is: Nodes of brackets are attached to nodes of bolt connector (bolt connector is just 1D element) and we are setting the constraint on those 1d element..is that right?

 

[rb1957]

is SW simulations a canned FEA included with SW the drafting s/ware ? Sounds like it if you can't "manually" mesh the part (when I mesh the s/ware automatically meshes the part and I can adjust the mesh as I think suits). I'm not a fan of these FEA tools as they are usually very limited in what you can do and constraints are often limited to design features, which maybe not what you really want.



another day in paradise, or is paradise one day closer ?

 

[FEA way]

The way bolt connector is handled internally is explained in the documentation chapter "Bolt Connectors - Formulation". There you can also find a picture that should make it clear for you how it works. Basically, a beam element is used for a shank and rigid "spiders" connect both ends of this element to the surfaces of joined parts.

 

[NRP99]

Search online "Bolt Pattern Force Distribution". Manual calculation is somewhat tedious but still worth doing to understand the physics better.

I do not think there will be much variation in forces if you make the mesh fine depending on how software calculates the forces. I think that these are reactions force and should not be changing in case you adopt approach 2 if approach 1 is not working.

May be, approach 1 can give you exact result. Try a simple problem with single bolt and check what you are missing from help documentation as suggested by others.

 

[petb]

kaffy,

What's the objective of your calculation? To design/check the anchor bolts?
I'm all for the use of FEA, but for anchor design it is often not necessary.
Anchor bolt suppliers often provide excellent formulas or software to conservatively design fasteners for the most common type of loads, brackets etc. Building code requirements are normally taken care of as well. For Hilti the software was called Profis Anchor at least a few years ago.

Hope this helps
PB

 

[kaffy]

@Rb..Yes, It is just an add on solid works drafting software.

 

[kaffy]

@FEA way..Thank You very much

 

[kaffy]

@NRP99 Thank you very much...I guess, I can do both method 1 and method 2 and then do a rough comparison between results. I recall seeing an online calculator for out of plane bending in bolts. I couldn't find it anymore..

 

[kaffy]

@Petb,

Yes, I want to check both anchor and the design of plate. I think I can use the split line and find if the steel design works and then separately check anchor bolts to see if they works
I saw profis the other day but unfortunately we have a stock of anchor bolts from other supplier (dewalt). Dewalt has a similar software but poorly designed and doesn't have a lot of options like hilti profis. I was thinking to use profis and set the anchor bolt size and then may be find some similar product from dewalt