Hi,
I tried to model a reinforcement concrete beam in abaqus and conduct it in cyclic twist, but when twist returned to zero and goes to negative phase, my model has stiffness. During cyclic twist applied experimental result show something different and column has no stiffness until it goes to negative phase. This effect is called pinching, and I use concrete damaged plasticity with plastic behavior for steel.
Pinching cannot be addressed in a general purpose software such as Abaqus/CAE. However, monotonic behavior of RC elements can be simulated with good accuracy in Abaqus as there is no pinching during monotonic loads.
As a result a good alternative is to adopt a hybrid modeling technique. Obtain envelop curve from Abaqus and then use a professional software to simulate its hysteretic behavior. This can be done either in SAP through Link elements with Pivot-type multilinear plastic or in OpenSees with Hysteretic or Pinching4 materials. In this way you need to calibrate hysteretic parameters of the used professional software (stiffness/strength degrading as well as pinching parameters) through experimental results.
Pinching cannot be addressed in a general purpose software such as Abaqus/CAE. However, monotonic behavior of RC elements can be simulated with good accuracy in Abaqus as there is no pinching during monotonic loads.
As a result a good alternative is to adopt a hybrid modeling technique. Obtain envelop curve from Abaqus and then use a professional software to simulate its hysteretic behavior. This can be done either in SAP through Link elements with Pivot-type multilinear plastic or in OpenSees with Hysteretic or Pinching4 materials. In this way you need to calibrate hysteretic parameters of the used professional software (stiffness/strength degrading as well as pinching parameters) through experimental results.
thanks mr. Mousavi for your good answering
but I have many essay about torsional concrete modeling in abaqus by prof. Han,
he made many model in abaqus and compared to experimental result,
and sure enough, test and model has a good adaptation,
but he didn't publish how did it in abaqus
If you seriously insist to do the job in Abaqus, you need to use a UMAT to resemble hysteretic behaviours. In any case parameters of the UMAT should be calibrated by experimental results. Accordingly, Abaqus would give you nothing more than professional software. As the most advanced hysteretic models are currently available in professional plarforms like NSPECTRA, IDARC, SAP, and OpenSees.
I get this effect in ansys . It took me some time to make exact code on workbench but finally it worked
abaqus can't model pinching effect cause the only material which could model dynamic effect is CDP for concrete and its codding is not good for pinching effect read this artical: Peter Grassl , Milan Jirasek, "Damage-plastic model for concrete failure," International Journal of Solids and Structures, vol. 43, p. 7166–7196, 2006.
but ansys has good one
sincerely vahid nazari
Vahid Nazari sir will your please share with me the procedure of including pinching in workbench concrete model.
will be very thankfull
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