Hello everyone. I am a beginner in mesh analysis. I would like to model a wooden beam on which there is a concrete slab connected to this beam using metal connectors. Can this be done in Prepomax?

it seems to be possible by compound part features of PrePoMax when cohesive zone of slip resistant between shear connector (steel) and wood or concrete being ignores. Adjacent nodes become continue in mesh, but separation also available to be use in contact or constraint.

there’s work around about these limitations using tied contact type parameter adjustment, but still need to validated and benchmarked before applying in model.

It depends on whether you want to include the connectors or ignore them in a simplified model. There are different levels of approximation that you can use in an analysis. From just putting one part on top of the other and applying tie constraint, to modeling all the connections in detail.

Look for some research papers on this topic, like “Structural response of timber-concrete composite beams predicted by finite element models and manual calculations” by N. Khorsandnia et al.

Indeed, spring connection models are common used for 1D beam and 2D plate element. In case of solid element, each of the part interactions are play important role.

below my example of reinforced concrete beams using solid compound feature of PrePoMax, modeling approach can be generalized to be use in composite section and material also.

Could you send an example so I can study it. Please and thank you in advance

hi, what’s your software previously used and analysis model successful reported? any documentation, so i can be doing comparison to PrePoMax workflow and CalculiX.solver capabilities.

since it’s interesting topics, i just recreate sample model below. Simple select all part in model, right click then select Create Compound Part in menus. After meshing, each part can be set to different material.

regarding to model section of wood beam and concrete slab interaction, it seems to be hard to achieve fully composite behavior due to low pull out strength of steel shear studs.

Hello, I find this topic very interesting, and I have a question that has arisen. Please excuse me as I am learning, and it is likely a very basic question.

In the case of reinforced concrete, the bond between steel and concrete is not considered a failure criterion in the design phase. Failure occurs due to the depletion of either the concrete or the steel. In this case, a reinforced concrete beam model using a composite solid is realistic.

In the case of a wooden beam and a concrete slab, the composite solid implies that the contact surface between the wood and the concrete slab [correct me if I’m wrong] is capable of withstanding infinite tangential stresses, which is not realistic if we want to analyze the behavior of the connectors. These stresses can be analytically calculated using the Collignon-Jourawski formula.

The tangential stresses supported by the contact surface between the wood and the concrete slab must be absorbed by the connecting fasteners, working in shear, and are limited.

Taking advantage of this conversation, I would like to ask how one can accurately model adhesion stress between two contacting surfaces, such as the adhesion stress between concrete and steel in a reinforced concrete beam.

Thank you very much for your assistance.

In general, bond slip resistance between concrete slabs and wooden beams surface are usually low and ignored. Full 3D FE model can induce some amount values due to frictional contact at point load areas.

Shear forces mainly transferred by steel studs or bolt/scew, to satisfy equilibrium bending occurs internally in studs also tension side at support. Material failure around studs end lead to large deformation, thus make it fail by pull out forces.

Probably, these condition in usual behavior can be different. Many parameters such as dimension and material strength of each part will affect the results.

it’s actually a complex thing, bond stress occur non-uniformly due to ribs geometry at main bars. However, simplification and assuming to be monolith by continuous mesh still can give useful results but probably in lower bound.

in case of plain bars, it can be neglected by assuming to allow in sliding mechanism or setting to percentage of resistance.

This reminded me of a long but interesting thread on the CalculiX forum: No separation contact - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).

Indeed, thanks for bringing an interesting topic. It leads me to further exploring.

The Calculix forum thread is very interesting and allows me to keep progressing. Thank you very much, everyone, for your assistance.

Can I ask you for the model file of this reinforced concrete beam? How do you model the connection between reinforcement and concrete?

Thank you in advance