I am currently modelling a reinforced concrete beam in ABAQUS software. It's incremental static loading that goes from STEP 1: zero to 10% (of the maximum allowable load), then zero. After this I added step of linear perturbation of natural frequency. Then i add 20% static load and then again frequency step and so on...
My natural frequency is coming out to be almost twice the natural frequency as reported in the research article that I am trying to model in abaqus.
I'm using damage plasticity model for concrete. My question is, by adding different support conditions (stiff steel plates) as supports, can there be a significant change in the natural frequency or not?
I want to make sure the modal frequencies match to certain degree before i proceed to the Dynamic steps.
I'd appreciate your help in this regard.
ThankS
Good morning. Thanks a bunch - I will read it and try to get help from it. Have a nice day!
Regards
~usman
If your beam is behaving in linear stage, the damage model does not influence your natural frequency at all. In such case, the incompatibility between your model and the lab results could mostly due to:
1. Non-homogeneous material property of the lab specimen which you may not have properly accounted for in your ABAQUS, or
2. Boundary condition especially at the support. I have experienced an increase in natural frequency of a simple steel-beam, that is ONLY due to the difference between support condition, especially if you are using the in-built support reaction.
Dear Usman,
did the model work?
i'm still just a beginner in abaqus, i have a very similar problem to yours
i really need to see your abaqus model for learning purposes, could you send it to me through my email please ? i would be so grateful
Regrads
- the deviation between simulative (Abaqus)and experimental (shaker test) result is found as 20% in my case.
- In my point of view, concrete damage plasticity is not suitable when natural characteristics are your aim because of linear behavior.
are your natural frequencies without load coming out correct?
if so then try to add load as a pressure.
hello dear colleagues, request for help (vibration study)
in Abaqus I use this option (image):
what kind of study am I using? and I declared a force (force function of time); in a beam in bending three points. how can i extract the resonance?
@ali benouis
You must have defined static step to apply load.
To obtain frequencies you have to define a step selecting linear perturbation and then define range of frequencies you need to obtain after loading step.
Nikhil Mahar
thank you
what I did, I declared three steps,
the 1st:
2nd:
and the 3rd:
what to sign: use damping data? and critical damping fraction !!
cordially
@Ali Benouis
I don't get your question.
Here is what I can suggest you as per my understanding of the question:
Step1: apply static load ( define amplitude curve)
Step2: from linear perturbation select frequency step ( define no. Of frequencies you need to obtain)
I think you are applying varying static load by defining amplitude that varies with time, so you don't have to run dynamic analysis.
Just create above 2 steps and run the analysis
- Badges
- Science topic