Why is reduced panel results TRz values =0 but Fx and Fy shear forces show values

[HRahmanMKEP2]

Have modelled some panels to represent a core under load cases such as dead, live and wind. I am mainly interested in the base shear reactions for wind load cases.

Issue: When viewing Fx and Fy reactions under diagrams I can see the results, however when going to the reduced panel results to view the out of plane reactions on the bottom cut TRz the values are all showing 0?  TRy on the other hand (in plane reactions) are showing values.

Question: If anyone could suggest what may be the possible reaosn the TRz values are showing as zero, I though they should be at least similar to Fx/Fy forces.

I have attached the robot file. All help appreciated thanks!

[Krzysztof_Wasik]

Hi  

Reduced results for panels forces direction correspnds to panel cut loacal system (not global system of coordinates)

TRx is force perpendicular to cut line  in panel plane

TRy is force parallel to panel to cut line in panel plane

TRz is force perpendicular to panel plane

Refer to

Reduced results for panels in Robot Structural Analysis

TRz in reduced panels table represents shear forces in direction perpendicular to panel plane. For box/rectangular section loaded with shear force, loads are  transferred mainly by panels parallel to load direction. Those forces are represented by TRy in reduced forces for panels table. Results for TRz can be close to zero because panels perpendicular to load direction do not participate in shear forces transfer.

For load direction presented below  (horizontal direction of rectangular core wall) and horizontal panel cuts at panel bottom edges, I would expect

- significant FRy (non zero) values in panels parallel to load direction (1, 3)

- almost zero TRz values for panels 1,3

- almost zero FRz and TRz values for panels perpendicular to load direction (2, 4).

I hope that this explanation will help

In my test model it looks as follows.

[HRahmanMKEP2]

@Krzysztof_Wasik  This makes good sense thank you! Just some follow up queries I suppose based on the above:

1. You mentioned TRx did you mean NRx as there is no TRx in the reduced panel naming convention?

2. For the box section diagram does that mean when a load is applied then that load is effectively distributed mostly to the walls parallel due to stiffness being higher based on the wall orientation?

3. In your results in what scenario could we get high TRz values as even in your table they are nearly 0.

4. Just a fyi: the model I have attached in the wind load cases applies loads in all 4 directions , the wind load and then 3 section loads going outwards I would expect TRz to not be0 but in this case it is any thoughts on this?

[Krzysztof_Wasik · Accepted solution]

Hi @HRahmanMKEP2 

ad1

Yes I missed correct name . I had Nrx in mind

TRx is force perpendicular to cut line  in panel plane

TRy is force parallel to panel to cut line in panel plane

TRz is force perpendicular to panel plane

ad2

Yes. Horizontal forces (their main part) are transferred by walls parallel to load direction. It is like in member section. Shear force is transferred by web - vertical section part if you will load section with vertical load.

ad3. In my test model I am presenting expected structure behavior. Horizontal loads transferred by core walls segments parallel to load direction. I do not expect significant TRz values for core walls segments. They will be larger if you will remove core walls segments parallel to applied horizontal load direction 

ad4.

I see that you have used material with shear modulus G equal to zero for walls simulation. You should obtain non zero (but still small) TRz values if you will change material to any of default material - with shear modulus G not equal to zero ( for example to C50)

[HRahmanMKEP2]

@Krzysztof_Wasik 

This the the culprit the shear modulus! thank you very much! I have changed it to a default material and got some realistic out of plane shear forces. I suppose because the shear modulus was 0 before it was acting like a fluid providing no resistance hence no reaction produced as its free to deform in shear.

Just one more thing, how would I edit the existing material to change it from 0 shear modulus to the correct value?

[Krzysztof_Wasik]

Hello @HRahmanMKEP2 

If it is not default materisl I would recommend

• Saving it to current material database with Geometry >Materials
• Edit its properties from Tools >Job Preferences >Materials

I would make a material instance copy (with slightly modified name) and update missed properties.

Refer to video

Have a nice day

[HRahmanMKEP2]

@Krzysztof_Wasik  Thank you for your time!   I will accept solution