How to make Shear Failure Model ?

[ankurjain1992]

Sir, How can I make a shear failure model in STKO opensees ?

Suppose I have a structure on the hill. Therefore, some column will be smaller in length and some are bigger in length. The Smaller Column will have tendency to fail in shear.

Thus, I need to make Shear Failure model ? How can i do that in STKO sir ?


Thanks in advance.

[STKO Team]

In our website's training page (https://asdeasoft.net/?stkowebinars-for-opensees) you can have a look at the 5th webinar: #05 Learning Opensees: Nonlinear Modeling of RC Frames (Distributed Plasticity).
There we explained, among other things, how to include a nonlinear shear behavior in a distributed-plasticity (fiber-based) force-based beam column element.

You can download the files in the link on the right, and you can watch the webinar recording on our youtube channel. At 1:03, we start taliking about the shear in beam/columns.

[ankurjain1992]

Dear STKO Team,

Seeing your e-learning tutorial, I have been able to implement a shear failure model for my structure's short columns. But one problem is that when I am applying the ModiMKPinching material to the column through the section aggregator, there is a huge change in my building periods. Without applying the Shear Failure model, T1 = 0.5317 sec but after I apply the
Shear failure model, T1 = 0.71 sec.

So my question is that is it normal for the period to get increased. In order the decrease the period, I have to increase the Elastic Stiffness, Ko of the ModiMKPinching material, so shall I do it ???

[Clarabella]

The period increased because you added the elastic shear stiffness to the flexural stiffness

[ankurjain1992]

yes so is that normal ?

increase in periods will cause change in the building response.

Any way that the period remain unchanged ?

[marafini.f]

As you know changes in stiffness and mass affect the building intrinsic dynamic characteristics as the frequencies.
No way you can change your model stiffness and obtain the same periods.
What's wrong with the new periods?

[ankurjain1992]

With the new periods, the building response will change.
In one of the excel to calculate the parameters of ModiMKPinching that is provided by you, there is the value with the name K,Regularised which is 100 times Ko. What is the use of this value and when to use it.

[STKO Team]

In that webinar we were talking about lumped-plasticity with zero-length hinges.
Since the hinge is zero-length, it should provide a rigid-plastic response, while the elastic part is given by the elastic beam element.
However, you cannot make K (of the zero length) = infinity, so we suggested to make it 100 times larger that K0

[ankurjain1992]

So this excel file that you posted can be used for calculating the parameters of ModiMKPinching for the Shear failure model (RC Short Column) like theta_p, theta_pc etc. ?

Also, instead of Ko evaluated in this excel file, we replace it with K.Regularized and use it as Ko.?

[STKO Team]

So this excel file that you posted can be used for calculating the parameters of ModiMKPinching for the Shear failure model (RC Short Column) like theta_p, theta_pc etc. ?

You need to compute them in such a way that the uniaxial law represents what you want to simulate, in your case the shear behavior of a RC Short Column. Regarding the shear strength/ductility of your specific column, it's up to you to compute them.

Also, instead of Ko evaluated in this excel file, we replace it with K.Regularized and use it as Ko.?

Yes