Shear force in two directions plus a torque (bidirectional shear and torsion)

[ZhichengT]

I am a python beginner, the question may be a little stupid, please forgive me. I want to know if "Section_properties" can output a three-dimensional envelope similar to biaxial bending as "Concrete_properties", because I have difficulty in trying to output the relationship between the shear force and the torque of the reinforced concrete section in "Concrete_properties", so I try to use "Section_properties" .
But I did not find relevant examples or methods. My idea is to be able to construct the output of a T-Vx and T-Vy resistance curve, and then be able to output the T-Vx-Vy three-dimensional envelope surface, similar to the biaxial bending calculation can output N-Mx-My.
Sincere respect!

[ZhichengT]

I currently have an approach where I take a range of
torque values (from -2e8 to 2e8),
and Vx and Vy values (from -2e10 to 2e10).
Then, for each torque value, I loop through the combinations of Vx and Vy, ensuring that the shear stress for each T-Vx-Vy combination does not exceed the allowable maximum shear stress of the section.

However, the maximum shear stress of the section seems to be different from the ultimate stress found in 'Concrete_properties.'

How should I determine the maximum shear stress that a section can withstand? Can simplified formulas from codes be used to calculate the ultimate shear capacity of the section?"

Sincere respect!

[robbievanleeuwen]

However, the maximum shear stress of the section seems to be different from the ultimate stress found in 'Concrete_properties.'

Could you provide an example of your code? Are you sure you are using the same input?

How should I determine the maximum shear stress that a section can withstand? Can simplified formulas from codes be used to calculate the ultimate shear capacity of the section?

This is not really a question that I can answer for you as it depends on what design codes you are using. sectionproperties is an analysis tool, however the design of cross-sections is outside its scope.

[ZhichengT]

Thank you very much for your reply. My initial explanation might not have been accurate. At first, I tried to output shear stress in concreteproperties, but after reviewing the code, I couldn't find any shear-related content. Then, I found the sectionproperties code and noticed that its examples include calculations for sectional shear stress. So, I wanted to try outputting a shear-torsion envelope similar to the biaxial bending envelope in concreteproperties, as a safety indicator for my section's resistance.

However, when using the example in sectionproperties/stress_analysis.ipynb, I noticed that for the same two sections, adding reinforcement increases the stress in the nearby concrete. (The example code is attached.) Could this lead to premature concrete failure despite the reinforcement?

Lastly, I want to mention that I am a beginner in Python. Right now, I can only use the example codes provided in your compressed package and cannot write my own code yet. Some of my questions may seem basic, so I appreciate your patience.

Sincere respect!
steel_python_code.docx

[robbievanleeuwen]

Hi @ZhichengT, sorry have only just got around to having a look at this. I think there are a couple of things going on here.

1. You are getting stress concentrations near the interface of materials, I would suggest changing n_points from 4 to 16 to improve this.

2. The overall shear distribution is not really changing a whole lot between the two analysis cases - this is expected as longitudinal reinforcement does not really add much to the shear capacity. Below is are two plots comparing the concrete shear stress, setting stress_limits=(0.0,2.3). Everything above 2.3 MPa will be shown in white. You can see that the shear stress distribution is very similar between the two plots (only some local increased stresses near the reinforcement, which is expected).

Unreinforced

Reinforced

Let me know your thoughts on this :)

[ZhichengT]

Thank you very much for your reply to solve my confusion
Sincere respect!