asdeasoft.net

Dear STKO Team,
I am currently working on analysing shear connections between aggregate masonry units. In order to effectively face this issue, I am interested in implementing a friction-cohesion behaviour for the interface between these units. Specifically, I would like to use a ZeroLengthContactASD element to simplify and speed up the execution of the model. However, I have troubles in incorporating cohesion into the model, as the ZeroLengthContactASD element does not accept cohesion as an input property.
To understand how to introduce cohesion into the model for the interface, I considered as reference the work conducted in the lecture #024 of the Advanced E-learning Course (T02_solid2solid_contact) and I used it to investigate the various behaviours of zero length element types.

To begin, I conducted tests using the zeroLengthContact3D element with cohesion values of 0 and 1.. The results show a tangential stress “jump” of 1 MPa in the first case compared to the second one (which corresponds to the cohesion presence).

I would like to obtain such a “jump” (cohesion effect) by using the ZeroLengthContactASD. From the available parameters, ZeroLengthContactASD allows to simulate only the case in which cohesion is zero, but I couldn’t find a way to take into account the presence of cohesion too.

My attempt was to introduce the zero-length physical property for the zero-length element and assimilate it to a constitutive law that could be as similar as possible to the cohesion effect. I associated a perfectly plastic linear constitutive law to the zero-length material and considered several parameters. Even by adopting exaggerated parameters (not physically possible) the model does not seem affected at all.
Unfortunately, in all the tests the solution does not give the desired result and the curve (Ut-Tau TRIAL) remains the same as in the Zero Cohesion case.

Is there a way to account for the cohesion effect and use ZeroLengthContactASD?
Thanks in advance for your help.

You cannot directly add cohesion to the ASD Contact.
But you were right with the trick you proposed (almost).
You cannot assign a zeroLength material to an interaction with a ASDZeroLengthContact element. Instead you need to duplicate the contact interaction.
In this way the first will have the pure contact, the second will have the pure plastic behavior (cohesion only).
Since they are 2 zero length in parallel, their contribution will sum up.
Note that for this, I had to reduce the Kt in your contact by 1/2, and I used the same value for the stiffness of the cohesive material, so that they sum to Kt in the coupled model