# Shear between slab and precast beams

How can i obtain shear forces in the interface between two concrete parts of a section casted in different stages taking into account the influence of different creep and shrinkage of the two concrete parts?
For example i want to calculate the shear forces between a precast beam and an in situ slab in a typical deck with I precast beams and a top in situ slab. It is also a typical problem in composite bridges where connection elements must be designed.
I have tried using shear cuts type interface but apparently the differential creep and shrinkage behaiviour is not taken into account.

Hello Pablo

There are different ways to calculate the shear stresses. It depends between which elements the section is located. You can either calculate the behaviour between a SAR and a beam or between the construction stages of a cross-section (BEAM). Therefore, I would suggest to have a look at our tutorial on composite bridges. Therefore, I would suggest to have a look at our tutorial on composite bridges. There we show the calculation of shear stresses between two different construction stages.

https://www.sofistik.de/documentation/2022/en/tutorials/bridge-design/composite-bridge/composite-bridge.html

Best regards
Frederik Höller

Thank you for your kind response.
The example you mentioned is not useful to me. As i mentioned in my post i am using teddy and the example is not in Teddy. After conversion of the example to dat files, I can see the concrete top slab of the composite section is modeled with PLAT commands.
I am modelling a deck where different parts of the section are casted at different stages.
My modelling approach is using construction stages in a cross-section (BEAM). The different stages in the cross section are modeled using POLY command, and we need to verify the construction joints between these different cross section parts.
As i mentioned in my post i was trying to get the joint shear forces with CUT but apparently the shear forces coming from internal differential deformations are not considered (differential shrinkage for example) in the CUT results.
Any suggestion?

Maybe “csm37_composite_nonlin_temp.dat” in CSM/design is a good example.

Or “csm3_composite_beam.dat” as concrete only.

Thank you ragl
Example csm3 is very close to what i need. In this example a concrete beam is casted in two stages.
Two cuts are defined in the section, but unfortunately those cuts are both in the first casting. There are no cuts in the interface between the two partial sections.
Is it possible to obtain shear forces between those two partial sections including creep and srinkage?
Any help is apreciated.