Softening Issues in Reinforced Concrete

- January 23, 2025 at 9:26 am
  
  giorgio.pedretti
  Subscriber
  
  Good morning everyone,
  I am working on a beam-column joint in reinforced concrete using ANSYS with a nonlinear concrete model. I am following the example provided in the ANSYS manual, "Chapter 54: Reinforced Concrete Joint Analysis," where a force-displacement graph is shown, highlighting both the hardening and softening phases.
  My goal is to achieve a similar result for my specimen. However, I am unable to reproduce the softening phase, even though I have used the same settings as described in the example.
  Could anyone provide some advice? I’m attaching my results: the blue curve represents the experimental data.
  Thank you very much in advance!
- January 30, 2025 at 12:24 pm
  
  John Doyle
  Ansys Employee
  
  It is hard to say for sure. Assuming your element technology, material set up and analysis specifications are the same, perhaps the FEA is not fully representing the test used to generate the experimental curve. From the emperical test, what was the conclusion about the mode of failure that caused the stress-strain curve to go negative. Was it the concrete material failing in tension or compression or was it slipping between the concrete and the fiber reinforcement? Did any fibers break? Why does the experimental curve show softening, hardening and then softening again?
  Perhaps your FEA is not capturing the root cause of failure produced in the lab.