LOAD STEP doesn't converge in ABAQUS

[Ingeniosus]

Hi everybody!

I'm modeling a RC slab under fire condition in ABAQUS.
The thermal analysis result is correct and converge, but when I want to do a Static analysis I create a LOAD STEP (where there are only static load) and it doesn't converge anymore.

The ABAQUS error is: TIME INCREMENT REQUIRED IS LESS THAN THE MINIMUM SPECIFIED

I have a TIME PERIOD: 1800
Initial increment 60 minimum 5E-2 max 60


Why it doesn't converge?

Regards

 

[mechfeeney]

Isn't that error suggesting that your 5E-2s increment time is too large? The solution is stepping to much from one increment to another and is diverging. That is a ridiculously long time period (I guess it's 30 minutes...but still). I'm not sure how Abaqus can handle that time period.

Try dropping your minimum increment down a bit and see what happens. You should also double check your model to make sure it is fully constrained, your material properties are correct, your loading is properly setup, etc. You gave a very vague description (without pictures) of your model, so there are numerous possibilities of the problems.

 

[corus]

Difficult to say when you say nothing of the problem, Is there contact, non-linear materials, etc? The time period of 1800 isn't unusual if you're loading a transient thermal analysis as it's convenient to match the static load step with that of the transient. Try a smaller initial time step if it's a sudden thermal shock where stresses can initially be very high.

Tara

http://tinyurl.com/4ydjg7m

 

[Ingeniosus]

Time step 1800 means 1800 seconds (half hour) and the time increment 60 seconds is to have results every minute (60 seconds) of analysis.

The analysis consist in a thermo-mechanical analysis of a RC slab under fire conditions.
I made a thermal analysis before and then I use the temperature results to start a static analysis with material non-linearities (I'm using a CONCRETE SMEARED CRACKING model for plasticity).

I can't understand why it doesn't work. (Other analysis work perfectly with this range of STEP: min 5E-2 max 60)

Thank you

 

[mechfeeney]

Corus was referring to your initial. You start 1 minute in, try starting at 1 second or something.

 

[Ingeniosus]

All model seems to be correct, so time increment is the key of my problem.

Ah ok. So that could be the problem?
I will try it!

Thank you all for your tips!