You are right, only uniaxial stress versus strain is needed.

In Abaqus, five confinement factors are needed to define before modeling, such as dilation angle and compressive stress ratio under biaxial loading, etc.

Hi Hermano Cardoso,

I am not sure what confinement means in your context. If you were talking about confinement behavior of concrete in a material parameter's level, you probably need to consider how to define these five factors by following Prof. Yang's suggestion. If you consider confinement of the concrete core caused by steel columns, which is a behavior between structural components, I would expect the software should automatically consider this mechanical behavior if you define the BCs correctly. However, under some situations, additional consideration in your FE model may be needed due to different features such as applying different connections or construction details in practice. 

Hi

The real life behaviour of concrete filled steel columns is better approximated by the Drucker-Prager yield criterion (SHEAR CRITERION=HYPERBOLIC). This is based on a number of references, where the confined concrete material properties under fire were evaluated. My experience also show that better match of experimentally recorded fire resistance rating (FRR) is obtained if the Drucker-Prager yield criterion is used. The following references might be useful for your project:

1.      Ana Espinos, Manuel L. Romero, Antonio Hospitaler: Advanced model for predicting the fire response of concrete filled tubular columns, Journal of Constructional Steel Research 66 (2010) 1030_1046.

2.      T.T. Lie: Fire resistance of circular steel columns filled with bar-reinforced concrete, Journal of Structural Engineering 1994.120:1489-1509.

3.      V.K.R. Kodur, M.A. Sultan, “Effect of temperature on thermal properties of high strength concrete”, Journal of Materials in Civil Engineering, 15(2), 101-107, 2003.

4.      F-P. Cheng, V.K.R. Kodur, T-C. Wang: “Stress-strain curves for high strength concrete at elevated temperatures”, Journal of Materials in Civil Engineering, 16(1), 84-94, 2004.

5.      Ana Espinos: Numerical analysis of the fire resistance of circular and elliptical slender concrete filled tubular columns, Doctoral thesis, Universitat Polytechnica de Valencia, Spain, October 2012. 

Dear coleagues,

Thank you for all the significant answers.

I have been studying composite columns and performing numerical simulation since my master´s. Fortunately, I have been considering the uniaxial diagram and all these confinement factors all of you mentioned.  However, last month I read two papers that it was not very clear which type of diagram the authors were considering. These two diagrams were drawn in the same picture and some part on text it was written that it is essential to consider the confinement effect. I can admit that I was concerned about the possibility that I have been working in a wrong way. Well, I can say that I am relieved with all answers.

Professor Yang, It is a pleasure to have your comments here, I have been reading your studies and following you since I created my account in the research gate.

Professor Kong, thank you for all your comments and remarks.

Professor Mago, I have read some studies considering the Drucker-Prager yield criterion instead. I shall take attention in all  given references.

I think you do not need to consider confinement and those papers might referred to confinement caused by steel rebars in compressive strength which is required to be considered in simulation. 

I believe the method you have in your mind would be the better choice and the interaction confinement would be structural behavior not material confinement.

Regards

Arash

Hi researchers.

Abaqus is a finite elements based software and it uses only input data you provide. It has no knowledge about constitutive lows of steel or concrete or other materials.

For example if you model concrete using aluminium stress-strain curve it will just do the calculations.

So, in your model, you must consider the confined concrete diagram in the concrete plasticity model if you want to consider the confinement effect.

Note that other factors as dilation angle and compressive stress ratio under biaxial loading, are related to the concrete damage plasticity (used to control concrete damage under compression and tension stress) and have no relation to confined or non confined concrete. 

I suggest for you to use four-parameter Hsieh-Ting-Chen failure surface model which is available in DIANA software to include the effect of confinement,