Boundary condition Shear wall

[Larisa GR]

Could you share some data?

• Experimental results from which you obtained the elastic parameters of the mortar and units
• Cyclic imposed displacement history
• Cyclic response

Please find attached the loading protocol applied to the specimens and the cyclic response of the masonry wall. I realized now that the displacement amplitudes were applied at different rates so the test did not last for days. Maybe this has some influence on the cyclic response of the model? although it should not influence the monotonic one

For the experimental results of elastic parameter of bricks please referred to the the paper of Makoond et al 2020. The bricks used in my experimental campaign are the ones under the ID I(a) and I(b). The mortar is the one ID as MB.

Regarding the compressive strength of both constituents: In the case of the mortar, it was obtained from a large number of specimens cast during the construction of the walls (samples 160x40x40 mm3). In the case of the bricks, a number of units were radomly selected from all the bach, regularized and tested (Samples 100x100x45 mm3). I attach also some of the results. There is also more information in my paper Garcia-Ramonda et al 2020 (also attached)

Thank you very much for your help and patience. Let me know if I can provide you with more experimental information.

[STKO Team]

Looking at the data for bricks and mortar, it looks like the Young's modulus are much smaller...
But probably I misunderstood the dimensions you provided...

Bricks:
When you say

Samples 100x100x45 mm3

does it mean that the cross-area is 100x100, and the height is 45?

Same for the mortar.
Could you tell me what are the X-Y dimension (so that I can derived sigma from force)
and the Z direction (compression direction) so that I can derive strain from displacement (carrera?)

[Larisa GR]

does it mean that the cross-area is 100x100, and the height is 45?

Yes. X and Y direction is 100 mm while the Z direction is 45

In the case of the mortar the compression test is performed in cube specimens with dimensions 40x40x40mm3

Looking at the data for bricks and mortar, it looks like the Young's modulus are much smaller...

The young's modulus was obtained by means of correlation with dynamic modulus as presented by Makoond 2020, which were compared with experimental values obtained from another experimental campaign (not carried out by me) on the units comprised in the masonry under analysis.

[STKO Team]

Ok, so taking your Excel files with the compressive experimental data, and converting them to stress/strain it turns out that the elastic moduli of both brick and mortar are more or less 10 times smaller than those you input.

Look at the file with these changes, it looks more reasonable. There is still a slightly stiffer behavior after the first micro cracking, but this may depend on the cyclic test, or some small slip during the test

Play with it and see what happens

URMMonotonic.zip

(504.67 KiB) Downloaded 307 times

[Larisa GR]

Thank you very much for your help. I will play with these new values (and try to find an explanation for them being so low).

However, I've also modeled my diagonal compression test on the same masonry sample (same geometry same material) with the initial parameters (the ones that were in the *scd file I provided at the beginning of this chat) and the results are really good compared with the experimental ones.

Do you think that the fact that the diagonal compression test is monotonic while the shear compression test is cyclic is the reason for such a different response of the numerical model???

Thank you again for the amazing technical support! you are of great help!

[STKO Team]

You're welcome,

However, I've also modeled my diagonal compression test on the same masonry sample (same geometry same material) with the initial parameters (the ones that were in the *scd file I provided at the beginning of this chat) and the results are really good compared with the experimental ones.

Probably there is a difference in the material used in the experimental tests or something wrong happened in the tests. However, I obtained those reduced Elastic moduli from the stress-strain curve of your experiments on mortar and bricks. You can look at them and realize that the E modulus cannot be so high...

Do you think that the fact that the diagonal compression test is monotonic while the shear compression test is cyclic is the reason for such a different response of the numerical model???

No, cyclic tests induce some extra crack, in the first cycles, but not so much to reduce the elastic moduli by a factor of 10!