Shear flow along a triangular member

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Discussion Overview

The discussion centers around the calculation of shear flow along a triangular member, particularly focusing on the significance of the shear flow at a specific point (point O) and the implications of the shear center's location. Participants explore the relationships between shear flow, shear force, and the geometry of the section, with a mix of theoretical and practical considerations.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about how to separate the q(0) term and questions its physical significance, wondering if it represents the total shear flow at point O.
  • Another participant suggests that if point O is where the section is open, then the value of q(0) must be determined based on that condition.
  • A different participant argues that the shear center's location indicates the section is open, implying that shear flow starts at zero at the free end of the section.
  • In contrast, another participant asserts that the cross section is closed and questions the reasoning behind listing multiple values of q(0), suggesting a misunderstanding of the problem's context.
  • One participant corrects earlier claims about the shear flow equation, stating that with Vy = 0, the equations presented are incorrect, while also acknowledging the quality of the diagram provided.
  • A later reply admits that the previous assertion about q(0) might be incorrect, leaving open the possibility that it could represent the total shear flow at point O.

Areas of Agreement / Disagreement

Participants express differing views on whether the cross section is open or closed, leading to conflicting interpretations of the significance of q(0). There is no consensus on the correct interpretation of the shear flow equations or the implications of the shear center's location.

Contextual Notes

Participants note the dependence on the definitions of open and closed sections, as well as the implications of the shear center's location, which remain unresolved in the discussion.

into space
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Homework Statement


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Homework Equations


qs1(0)=qs3(5)
qs2(0)=qs1(5)
qs3(0)=qs2(6)

Vy=0

q(s)=-Vy/Iyy*Q(s)

Where Q(s)=y*A
Where y=y coordinate of centroid and A=Area

The Attempt at a Solution


To be honest I'm not sure how to separate the q(0) term, nor do I know what the physical significance of q(0) is (it's the shear flow, but is it the total shear flow at point O?). I've tried setting up the problem like:
qs1(0)=q(0)=qs3(5)=q(0) so q(0)=q(0)
but that doesn't give me any information. I've also tried:
qs2(0)=-7.5*Vz*t/Iyy+q(0)
qs3(0)=-7.5*Vz*t/Iyy+q(0)
 
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The shear flow q(s) is a function of the length coordinate s. Along each of the sides s1, s2, and s3, there is a point where s = 0. The location of the shear center suggests that the section is open at some point. If point O is the location where the section is open, what must the value of q(0) be?
 
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Thanks for the reply.

Hmm, I see what you are saying. So at s1=0, and the shear at point O is zero, then qs1(0)=-3*Vz*t*(0)^2/(10*Iyy)+q(0)=0 which means q(0) has to equal 0. Can you explain how you know there has to be an open section just from looking at the shear center?
 
The shear center is located outside of the triangular section. I believe most closed sections have the shear center located somewhere in their interiors. If the section is indeed open, then the shear flow starts with a zero value at the free end of the section. This fact is used when analyzing the shear flow in closed sections.
 
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into space: The cross section is not open. You can see, from the given diagram, the cross section is closed.

In section 1 of post 1, why are you listing five values of q(0), a through e? When you state a question, you need to explain what is being listed. Why are you listing those q(0) values? Are you saying this is a multiple choice question? Is this an exam question?

into space said:
q(s)=-Vy/Iyy*Q(s)
Wrong. Vy = 0.

into space said:
Where Q(s)=y*A
Wrong. Vy = 0. Keep trying. By the way, excellent diagram. Nice work.

into space said:
... nor do I know what the physical significance of q(0) is (it's the shear flow, but is it the total shear flow at point O?).
No, it is not. q(0) is just a constant. Your task is to determine the value of that constant.
 
Last edited:
into space: My first sentence in the last line of post 5 might be wrong. You might be right. q(0) might be the total shear flow at point O.
 
Last edited:

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