Force FEMAP to write a single SPC1 card using "THRU" instead of one for each node?

[RealSaladsamurai]

This is me being hyper picky, but assume I have a group of nodes that are sequential: "1001,2000,1"

It is evident that FEMAP is able to detect that they are sequential because when I select them, it shows exactly what I have above in the selection dialogue (i.e. 1001,2000,1) when I go to create a single point constraint (SPC).

But when I go to my .BDF file, it is written as one thousand individual SPC1 cards. Is there anyway to force FEMAP to write it as:

SPC1    1       456     1001    THRU    2000

instead of:

SPC1    1       456     1001
SPC1    1       456     1002
SPC1    1       456     1003
.
.
.
SPC1    1       456     2000

???

________________________
FEMAP v11.1.0
MSC Nastran v2013

 

[rb1957]

if you're looking at a .bdf file, then your question refers to Nastran rather than FeMap ...

or maybe to how FeMap writes a .bdf IF Nastran allows that format, which would surprise me.



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

 

[RealSaladsamurai]

Hi rb1957. My question, as stated, is how to get FEMAP to write the NASTRAN file as shown (if possible). So it is a FEMAP question. The THRU syntax is certainly allowed by NASTRAN. My guess is that this is wishful thinking.

________________________
FEMAP v11.1.0
MSC Nastran v2013

 

[rb1957]

could you fake it by making an RBS to join your 1000 points to 1 ?

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

 

[RealSaladsamurai]

Hi rb1957 - I don't see any RBS's in the NASTRAN QRG, but I am assuming that it's some sort of MPC. Again, I was just being a little obsessive compulsive about my input file. But now that we're talking about it, I am really going to show my ignorance here.

You may wonder why I would have thousands and thousands of SPCs in my bdf. Here is what I have been doing. If I have solid elements in my model, which do not generally support DOF 456, as well has other elements (or MPC) in my model, which do support rotational DOF, I manually SPC out ALL of the nodes that belong to solid elements. Why the heck do I do this? Because I like to do it manually and keep AUTOSPC = YES so that I can use the grid point singularity table as a "bucket" to catch anything that I may have missed. This is me being hyper-aware of my constraints so that I can track down improper model grounding.

Now to be honest, I am relatively new to FEM/FEA (maybe 2 years of industry experience) and even newer to FEMAP/NASTRAN (about 3 months .. prior experience with ANSYS) ... so this could just be me being obsessive compulsive without any good reasoning. I welcome any feedback or thoughts people have on this. This is how I learn.

________________________
FEMAP v11.1.0
MSC Nastran v2013

 

[rb1957]

"RBS" should've been "RBE".

I like your non-use of auto-SPC ! of course you can use auto-SPC then check that all the created restraints don't generate large reactions.

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

 

[Naffoussi]

Hi,

You can include this line in your analysis setting / Nastran BUlk Data Options / Start Text (Off):

SPC1 1 456 1001 THRU 2000

Give it a try without defining the constraints in Femap.

Hope this helps !

Seif Eddine Naffoussi, Stress Engineer

http://www.Innovamech.com

33650 Martillac û France

 

[BlasMolero]

Dear Samurai,
You can remove rotational DOF from solid elements automatically in FEMAP without writing any SPC1 card, neither using PARAM,AUTOMPC,YES: the key is to use commnd "MODIFY > UPDATE OTHER > PERMANENT CONSTRAINTS" > select all nodes from solid elements and next select the DOF you want to remove:

If you PREVIEW your analysis you will see that not any SPC/CPC1 card exist, the DOF removed are part of the GRID card !!.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[RealSaladsamurai]

@rb1957 - Thanks for your feedback! Good to know that I am not just an insane person ... well, that might not be a valid conclusion Also, it may just be that I haven't had my coffee yet, but how do check the reactions of these DOF? What should I be inspecting in my output?

@compositecurves - That's actually what I have been doing and what spawned my question. I know that sooner or later, we all have to manually edit our input decks. But for now, my line of thinking was that if I have to re-run a model with some adjustments, than I have to remember to update the model in FEMAP AND in the input deck. Giving myself 2 opportunities to make errors gives me great consternation ... but I guess I just have to get used to the idea and start being extra, EXTRA careful. Thanks for your input!

@Blas - Wow! I'll have to give this a try; it looks like it's exactly what I am looking for. I like the idea of doing the extra research to figure out to get FEMAP to generate a deck exactly the way I want to; this helps to eliminate extra opportunities for errors as I mentioned above.



________________________
FEMAP v11.1.0
MSC Nastran v2013

 

[rb1957]

@blas ... are the freedoms removed from the stiffness matrix, or effectively autoSPC'd ? I suspect the latter, as I've always understood that NASTRAN assigns 6 dofs to each grid by default.

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