×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Simple Frame analysis not working! I know this is simple!

Simple Frame analysis not working! I know this is simple!

Simple Frame analysis not working! I know this is simple!

(OP)
Hello...
I am new to ABAQUS and have a fairly straight-forward probelm (I hope!).   i'm trying to model a simple 2D frame made of steel I-sections. I initially modelled it with rectangular sections without difficulty.   However, when I changed the sections to I-Sections, it wont run! I have tried changing iteration parameters, to no avail.   Section orierntation is (0,0,-1).   Any other tips?    It is pinned at the bases and has a signle point load applied.

I'd greatly appreciate any insigiht!

Thanks,
K

RE: Simple Frame analysis not working! I know this is simple!

hi Kc97, When you say, it won't run, what do you mean? What are the error messages that come up in your monitor window?

RE: Simple Frame analysis not working! I know this is simple!

(OP)
Hello Opti...thanks for replying.

The error message reads:

"Too many attempts made for this increment

Abaqus/Standard Analysis exited with an error - Please see the  message file for possible error messages if the file exists."

And the .msg file says:
" ***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
             FRAME-1.1378 D.O.F. 6 RATIO = 9.63575E+009."

Thanks

RE: Simple Frame analysis not working! I know this is simple!

Is this the same node you have applied your concerntrated load on? This might be causing a problem reaching a solution. Are you considering geometric non-linearity (i.e. selecting the 'nlgeom' in your step module)?  How fine is your mesh, in the areas of importance? Hope this helps.

RE: Simple Frame analysis not working! I know this is simple!

(OP)
Every node displays this error (i.e. about numerical singularity). Not just the one that load is applied to.   In any case, there is no issue when I use a rectangular section.

I am using what I think is a very fine mesh (elements are 50mm long throughout the frame, whcih is 7450mm high and 30,000mm wide).

Thanks for any advice you can give!

I was wodnering if it might be something to do with the orientation?

K

RE: Simple Frame analysis not working! I know this is simple!

I am not an expert on numerical singularities, but I know they are common when modelling crack problems and can lead to convergence issues.  If you can post a cae file or picture, maybe we can offer some more advice?

RE: Simple Frame analysis not working! I know this is simple!

I've also had it caused by rigid body motion.  Does it also warn about unconnected regions?

RE: Simple Frame analysis not working! I know this is simple!

Depends on the element type, you might have pinned trusses instead of rigid beams and so the thing just collapses.  

Tata  

RE: Simple Frame analysis not working! I know this is simple!

(OP)
Hello,

No I have beam elements (B22 or B21 depending on the analysis) throughout the frame.

Thanks,
K

RE: Simple Frame analysis not working! I know this is simple!

Section properties missing so it has no stiffness?

Tata  

RE: Simple Frame analysis not working! I know this is simple!

(OP)
No I have included section properties for an I-section (h, b1, b2, I, etc....)

This is the problem...it works when the section properties are for a rectangle!

THanks for time!  I really appreciate it...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources