Hi colleagues,
I am currently working on shear strengthening of reinforced concrete (RC) beams using CFRP wraps and FRCC jackets. As part of my research, I am performing a finite element method (FEM) analysis of a four-point bending test on unstrengthened RC beams using Abaqus to compare with the experimental results. Here is a brief description of the model:
I am using the concrete damage plasticity model to simulate the non-linear behavior and post-cracking responses of concrete. All compressive and tensile properties, as well as damage parameters, have been defined based on recommendations from reference papers and design codes. The model employs roller support boundary conditions to match the experimental setup. For the mesh controls, a C3D8R is used for concrete while a T3D2 is used for rebars.
The force-displacement results from the experiment indicate a mixed failure mode, with initial flexural failure followed by shear failure. The FEM simulation accurately captures the section's capacity and aligns well with the experimental results. However, in the FEM I am unable to replicate the failure/drop observed in the experiment.
Do you have any suggestions on what might be causing this discrepancy?
I have attached some picture of the setup, model parameters and results for reference.
Mikias Mekbebe, achieving the post-peak deformation in your FEM analysis can be challenging due to the limitations of the static general analysis in Abaqus. The lack of an element deletion criterion means that the model does not reduce the capacity after failure, resulting in constant residual stresses. This could explain why your simulation fails to replicate the failure/drop observed in the experimental results. Such results are i think, only able to achieve with XFEM. I am not sure but that is what i have learned. May be Explicit solver will help you.
Engr. Tufail Thanks for the response. I have tried to use the explicit solver and enabled the element deletion by editing the model keywords but the response is completely different from the experimental results.
To address this discrepancy, consider verifying the accuracy of roller support boundary conditions in Abaqus to match the experimental setup precisely, ensuring consistency in load distribution and structural response. Additionally, review the mesh quality, element types (such as C3D8R for concrete and T3D2 for rebars), and their adequacy in capturing localized effects of shear failure, which can be more sensitive than flexural failure. Double-check material properties and damage parameters used in the concrete damage plasticity model, as minor variations can significantly impact failure mode progression. Lastly, scrutinize the post-processing methods and failure criteria in Abaqus to accurately identify shear failure initiation and progression, possibly adjusting these parameters to better reflect experimental conditions and observations.
Ram Kumar Thank you for the feedback. I would appreciate it if you could elaborate more on the last point regarding post-processing and failure criteria.
closely examine the stress and strain distribution in your concrete elements, particularly around critical regions such as near the supports and load application points. Look for signs of cracking, crushing, and significant strain localization. Similarly, analyze the stress and strain in the reinforcement bars, ensuring they are reaching their yield point in the expected areas based on the experimental observations.
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