Modelling masonry EFM

[mmc]

Hi again STKO!

I am trying to model a masonry wall in STKO following the equivalent frame method. I have watched your webminar on the lumped plasticity modelling of RC frames.

To do so, the panels will be beam-column elements with two flexural hinges assigned at the top and bottom. Additionly, I want to add a shear-hinge at mid-height of the beam. I have some questions:

• How can I add this shear-hinge at the middle of the frame? I have seen this other related topic but it is not defined viewtopic.php?f=36&t=1778.

• Since it is not a RC frame, I need to use any fiber-section element different from the rectangularbeamsection. I have seen that I could use just the fiber element defyning the section of the wall. What do you suggest?

• I want to perform a nonlinear static analysis. During the application of horizontal loads, the acting axial load changes from the inital value consequent to the vertical dead loads. Also, due to the redistribution phenoma associatted with the progressing of non-linear response, further variations may occur. Hence, the value of the corresponding shear strength varies in each panel. I am not sure if this could be considered by performing any parametric analyses. I have seen that in your webminar you changed the values of the concrete but you performed different analyses, not updating the input parameters each step of the analysis. SO, I am not sure if this could be possible to do.

• I have seen in youtube that you have already modelled a building following this approach but it is not in any of the webminars...so i guess that you might have already studied this issue

Thanks for your comments.

Regards.

[STKO Team]

How can I add this shear-hinge at the middle of the frame?

You have 2 options:

1. Use a section aggergator and add a Shear-Deformation law
2. Split the element in the middle, add a zeroLength element with a Shear-Displacement law

option 1) works only with Displacement-Base beams.
option 2) is generic. Don't warry about splitting the element and adding a zeroLenght, since all this stuff is made automatic with a new tool that we have in STKO.
Look at this file for a demonstration and let us know if you have any doubts:

Shear.zip

(26.42 MiB) Downloaded 213 times

Immagine 2021-10-11 094506.png (86.83 KiB) Viewed 4035 times

Since it is not a RC frame, I need to use any fiber-section element different from the rectangularbeamsection. I have seen that I could use just the fiber element defyning the section of the wall. What do you suggest?

Yes, use a simple Fiber section and create a rectangle and mesh it.

I want to perform a nonlinear static analysis. During the application of horizontal loads, the acting axial load changes from the inital value consequent to the vertical dead loads. Also, due to the redistribution phenoma associatted with the progressing of non-linear response, further variations may occur. Hence, the value of the corresponding shear strength varies in each panel. I am not sure if this could be considered by performing any parametric analyses. I have seen that in your webminar you changed the values of the concrete but you performed different analyses, not updating the input parameters each step of the analysis. SO, I am not sure if this could be possible to do.

Unfortunately, the shear hinge is a uniaxial material and it is uncoupled from the axial-flexural reponse.
The best you can do now is to run a static analysis, estimate the average axial load and create a shear hinge for that.
We are working on a coupled N-My-Mz-Vy-Vz lumped hinged, but it's still a work in progress

[mmc]

Thanks for your reply.

Look at this file for a demonstration and let us know if you have any doubts

Could you upload the .scd file to check the modelling procedure? It would be very didactic.

Regards!

[marafini.f]

mmc, the file is there! before the image

[mmc]

Yes, but it contains the .mpco file that I can only open with the post-processor. I would like to have the .scd file to open it with the pre-processor to check the modelling approach you suggested.
Thanks!

[STKO Team]

Sorry! my mistake
here it is:

Shear.zip

(153.62 KiB) Downloaded 266 times

[mmc]

Thanks for the file. I have been studying what you proposed.

I have been cheking your special purpose RCBeamColumnProperty. I have read some posts on this property and I am aware that it is still under development.

I was wondering if this element is related to the work that was proposed in this papers:
https://www.sciencedirect.com/science/a ... Ifr_H3IVCP
https://onlinelibrary.wiley.com/doi/ful ... U0YZTXsFfA

In the second one, a macroelement was proposed in OpenSees. They used FBE+fiber cross sections. Concrete02 to model the masonry fibers, And the hysteretic material to add the shear behaviour. I was wondering if this modelling approach could be used with the property that t is available in STKO. The formulation would be distributed distribution with a fiber cross section to model the panels (discretized with Concrete02). Then, in the center, a shear behaviour could be added using the predefined hysteretic material for each panel following the method proposed by the authors or other strength criteria. In the element properties, I could apply the FBE to the frames. It is just an idea but I am not sure if it could be possible. The authors added elastic fibers at the corners of the masonry panels to avoid convergence problems but I dont know if it would be needed with the STKO property.

Keep in touch.

Regards.

[STKO Team]

the RCBeamColumnProperty is just a way to automate the creation of beam-column elements, but it still under development.

However, what was described in that paper can be done with the Section Aggregator and a pinching4 or ModIK material for shear

[mmc]

Hi!
I have been using the RCBeamColumnProperty. I have found that when I select the "lumped plasticity with ZLhinge", some errors appear. The error says that I have to select a material for either Shear Vy, Vz and torsion T. Thinq is that at the ends of the beam, I dont want to add a shear hinge, I just want to add that in the middle. And also, I dont want to consider the torsion. Maybe it is a bug in the code of the element??? I dont have this problem with the other two approaches.
Regards.

[marafini.f]

Dear mmc,

the RCBeamColumnProperty is still under development. It is available for users as we were testing it with a few of them. The distributed approach s already been thoroughly tested, but the ones you are referring are still not approved for use.

We advice you to use the Section Aggregator and a pinching4 or ModIK material for shear.

Best,
Francesca