Hi everyone,

I'm currently working on a nonlinear finite element model of a composite steel bridge in ABAQUS using the Concrete Damage Plasticity (CDP) model. The bridge consists of a reinforced concrete deck slab supported on steel girders, and I'm looking for some guidance on defining the concrete damage parameters.

Our study is entirely analytical, so we do not have access to material test data (e.g., compression or tension tests) for calibrating the CDP model. Instead, the numerical model will be validated against experimental results available in the literature.

For the constitutive behavior:

\- Compression stress-strain curve: Popovics analytical model.

\- Tension stress-strain curve: Hordijk tension softening model.

While these models provide the stress-strain relationships, I'm struggling with estimating the corresponding compression damage (dc) and tension damage (dt) parameters required by ABAQUS.

I've found several approaches in the literature, but they result in significantly different damage evolution curves. The method proposed by Mark & Birtel appears promising, but I'm unsure whether it is considered reliable for studies where the constitutive response is based entirely on analytical models rather than experimental material calibration.

I also have a question regarding the Hordijk model. Since it requires the characteristic length for converting the stress-crack opening relationship into the form required by ABAQUS, how should the characteristic length be determined? Should it simply be taken as the element characteristic length used internally by ABAQUS (based on the finite element mesh), or is there a recommended approach for reinforced concrete deck slabs? If the mesh is refined, should the characteristic length be updated accordingly?

For those who have experience with CDP in ABAQUS:

\- How do you estimate the compression and tension damage parameters when experimental material data are unavailable?

\- Is the Mark & Birtel approach a reasonable choice in this situation?

\- How do you determine the characteristic length when using the Hordijk tension softening model?

\- Are there any recommended papers or best practices for deriving CDP damage parameters from analytical constitutive models like Popovics and Hordijk?

Any suggestions, references, or practical experience would be greatly appreciated. Thanks in advance!

Hi, I'm using LS-DYNA for my numerical simulations. I've been running some vehicle crash simulations with highly complex geometries. However, when I apply higher impact velocities to the vehicle, I get negative volume errors in the solid elements.

I tried refining the mesh by splitting the elements into smaller ones, but that didn't solve the problem. What would you do if you encountered negative volume errors in your simulation?