When can I treat a joint as a fixed conection?

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In summary, the conversation discusses the concept of treating a joint as a fixed connection and its effect on the pivot point of a beam. It is noted that despite the joint's inability to transfer moments, the pivot point remains in the same position in both cases. The conversation also touches on the mathematical definition of a pivot point and whether the entire structure is floating in space. It is clarified that the 100kg box is able to separate from the 10kg box.
  • #1
John Mcrain
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jiojo.jpg

Question is : is pivot point is both case at same position...

Useing only external forces (100kg,10kg and 30kg) I can treat joint as fixed conection and still get correct results,in both case pivot point is at same positon,even right case has joint at right side of beam..
How is possible that I treat joint as fixed conection and still get correct result,isnt this confusing becasue joint can't trasnfer moment ,only forces?When I can't treat joint as fixed conection?
Because joint can't trasfer moment only forces,so I can use internal forces inside joint and still get same results,pivot point is at same position in both case..
 
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  • #2
John Mcrain said:
Question is : is pivot point is both case at same position...
View attachment 278592
Define "pivot point " mathematically.
Is the whole thing floating in space?
Is the 100kg box free to separate from the 10kg box?
 
  • #3
A.T. said:
Define "pivot point " mathematically.
Is the whole thing floating in space?
Is the 100kg box free to separate from the 10kg box?

no in space,yes it can separate..
Pivot point is point below 10kg beam so beam is balance,stay horizontal..

jiojo.jpg
 

1. When can a joint be treated as a fixed connection?

A joint can be treated as a fixed connection when it is able to resist both rotational and translational movement. This means that the joint must have high stiffness and strength to prevent any significant movement.

2. What factors determine if a joint can be treated as a fixed connection?

The factors that determine if a joint can be treated as a fixed connection include the type of joint, the material properties of the joint, and the magnitude and direction of the applied loads.

3. Can a joint be treated as a fixed connection if it is welded?

Yes, a welded joint can be treated as a fixed connection if it meets the necessary criteria of high stiffness and strength to resist movement.

4. Is it always necessary to treat a joint as a fixed connection?

No, it is not always necessary to treat a joint as a fixed connection. In some cases, a pinned or partially restrained connection may be more suitable and cost-effective.

5. How can I determine if a joint is strong enough to be treated as a fixed connection?

The strength of a joint can be determined through structural analysis and testing. Finite element analysis and physical testing can help determine the stiffness and strength of a joint, which can then be compared to the required values for a fixed connection.

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