FEA problem

[ahsanparvez]

I am a new member to this forum.

I am working with a FEA program written in FORTRAN. I am analyzing the behavior of the reinforced concrete beams under constant amplitude cyclic loading. As for example: I am applying cyclic load range between 30 kN to 100 kN till the failure of the beams. I am recording the total number of cycles till failure and load versus deflection relationship as well.

Problem:

The deflection under maximum load (100 kN) is reasonable. Whereas, the deflection under minimum load (30 kN) at each cycle is underestimated in FEA, meaning that I am getting less deflection value than actually it should be. It indicates that the FE program is overestimating the elastic recovery during minimum load, thereby giving lass deflection.

I understand that I have given a general view of the problem and may be difficult for others to get full picture of the problem. However, if anyone can give me any hint I will be highly obliged.

 

[IDS]

How is the stress/strain behaviour of the concrete and steel modelled?
How is behaviour under loading and unloading modelled?
Does the analysis take account of the difference in behaviour before and after cracking, tension stiffening, etc?
Can you post some samples of predicted and actual behaviour?

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[ahsanparvez]

Hi Doug,

Thanks for your interest and reply. I have attached a snapshot of the results.

Please find to answers to your questions below:

Stress/ strain behavior under maximum load is nearly close to experimental, whereas, far below under minimum load.
Yes, the analysis take into account the tension stiffening.

Thanking you in advance.

Regards
Parvez