indeed, actually all parameter values of concrete properties should be derived from experimental testing. However, some approximating shown have correlation with compressive strength. The model part of concrete and steel reinforcement need to be configured and represent well, including main bars and stirrups. It’s commonly used by truss element or solid bars model, but probably not simplification by equivalent plate strips since it will lead to overstiffening the model.
classical Mohr-Coulomb material model reported overestimating the capacity due to large contribution in tensile strength, a modified MC available have improvement in Rankine (Tension Cut-Off). It can be increasing the accuracy when compared to Concrete Damage Plasticity (CDP) in Abaqus.
Interesting to do comparison of both analytical and experimental data with nonlinear FE results, plotting stress/strain over depth of section. An improvement in damage material model also possible to be use in CalculiX trough MFront.
p.s i’m also not familiar with European codes, frequently used ACI in practices, probably CSA, NZS or AASHTO can try to follow to understand.
On the side I have been working on modeling the rebar using the common node method. Much of my FEM interest involves large strains so better concrete models post cracking will be helpful, especially models that model shear at cracks to one degree or another. I am familiar (loosely) with the penalty method, but for real scale modeling (not lab samples) the mesh needs to be too coarse for effective modeling (I think). I am not familiar enough with material modeling or even compiling Calculix to use MFront, so I am hoping those more familiar will be able to get a good sample problem working. Since I am not in a position to propose research on that fundamental level, I may have to live with correlations with standard concrete testing for the concretes my employer works with, and with programs that model cracked high strain varying conditions well for simple structures, such as Response 2000, a spreadsheet.
I am mostly interested in what happens at failure and deep into failure, so I am interested in accurate prediction of the cracking process and post cracking behavior. Simple linear material models work well prior to cracking. My experience is simply due to lots of time, starting in the bridge office here in early 1969, and to a degree due to not having an engineering degree (physics instead) which meant through the decades problems for which the codes or current policies didn’t fit were thrown my way. I resisted moving into middle management so I could stick to the engineering for my entire career.
I don’t think AASHTO has much to say about material modeling. ACI may in more recent publications, but that is rather expensive. The ACI code itself is rather simple.
below my example of preliminary model checking in the past, i did try to model all reinforcement as solid, but resource become high in nonlinear analysis. So, i did not study further the physical behavior. Previously, testing on simple model using structured hexahedral and truss element still shown comparable result similarities with solid bars. Unfortunately, my preprocessor is not yet supported well in line element modeling.
