Concrete is brittle :P Anyways, without sharing abaqus file, it is not possible to put some conclusive remarks. Share your file warnings and status with me on https://wa.me/+923440907874

Engr. Tufail hi

Brittle failure in your UHPFRC-jacketed concrete column under 4mm deflection could be due to insufficient ductility in the model. This could arise from several factors, such as:

1. Material properties: The ultra-high-performance fiber-reinforced concrete (UHPFRC) may not be properly capturing the post-peak strain-softening behavior in your Abaqus model. Ensure the material properties include accurate stress-strain relationships for both concrete and fiber-reinforced materials.

2. Mesh sensitivity: A coarse mesh can lead to inaccurate stress distribution and premature failure. Refining the mesh, particularly near stress concentration areas, may result in a more accurate load-deflection response.

3. Boundary conditions: Inaccurate boundary conditions or constraints may cause unrealistic stress concentrations, leading to brittle failure. Double-check the boundary conditions and loading application in the model.

4. Plasticity models: The concrete damage plasticity or another constitutive model in Abaqus may not be appropriately calibrated to capture the gradual post-peak behavior. Adjusting parameters such as the dilation angle or damage evolution criteria may help achieve a more gradual load decrease.

By addressing these factors, the model should better simulate the gradual load decrease observed in the experiment.

Check the concrete and UHPFRC material properties, especially post-peak behavior, and ensure that damage or softening is modeled accurately to reflect the gradual decrease in load seen in experiments.

There is very tiny gap when I zoomed in

Steel Pipe - Solid Element create in Parts section - 3mm thickness

Rebar - Wire Truss element create in Parts Section - 6mm thickness

Interaction used - Tie Constraint

How connect - Welded (I hope Tie constraint is the best way of interaction for this occasion, if not please advise me best way to do this with some steps as I am kind of starter for this simulations)

Tried things

Use Tie pair with position tolerance of 1 and still did not work

Tried to cut this steel tube in to parts and then through the point I get give datum point exact location and. Use translate that rebar node to datum point, did not work - Because it is too close. Some error message 2nd point is coincidence and cannot do it.

Question - Please give me best solution to get accurate results how to use interaction between this two and avoid this error and what are the solution to avoid this space and use accurate interaction. Please help with this problem

Warning Error Messages -

For *tie pair (assembly__pickedsurf1023-assembly__pickedset1022_cns_), adjustment was specified but no node was adjusted more than the adjustment distance = 2.22000e-16.

For *tie pair (assembly__pickedsurf1034-assembly__pickedsurf1033), adjusted nodes with very small adjustments were not printed. Specify *preprint,model=yes for complete printout.