"Members of a frame are axially inextensible" implication?

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Discussion Overview

The discussion revolves around the implications of the axially inextensible condition of members in structural frames, particularly focusing on frames with vertical and inclined legs. Participants explore the meaning of this condition in terms of displacement and deformation within the framework of structural analysis.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that in frames with vertical legs, the length of the chord joining member ends remains unchanged in the axial direction during displacement.
  • Others suggest that the same principle applies to frames with inclined legs, indicating that the distance between the ends does not change.
  • A participant questions whether the point in the deflected frame should lie on the original line if a member is inextensible, leading to differing interpretations of the implications of inextensibility.
  • Another participant argues that the requirement for inextensibility is that the cumulative length along the member remains the same as in the original frame, suggesting a different understanding of the condition.
  • There is a discussion about whether axially inextensible members imply no axial deformation, with some participants expressing skepticism about this interpretation.

Areas of Agreement / Disagreement

Participants express differing views on the implications of axial inextensibility, particularly regarding frames with inclined legs and the interpretation of displacement. No consensus is reached on the exact implications of this condition.

Contextual Notes

Participants reference a diagram from a structural analysis text, which may be used to illustrate certain mechanics topics, but its role in the discussion remains unclear. The conversation suggests a potential reliance on simplified models before addressing more complex scenarios.

Ashu2912
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In analysis of frames, we say that "The members of the frames are axially inextensible". In context of frames with vertical legs, what I understand is that the length of the chord joining the member ends in the displaced condition would be same in the axial direction. However, what does it imply in frames with inclined legs?
 
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Ashu2912 said:
In analysis of frames, we say that "The members of the frames are axially inextensible". In context of frames with vertical legs, what I understand is that the length of the chord joining the member ends in the displaced condition would be same in the axial direction. However, what does it imply in frames with inclined legs?
Same thing. The distance between the ends doesn't change.

Chet
 
This is a diagram I found in "Structural Analysis" by Aslam Kassimalli. Here, if the member AC is inextensible, shouldn't the point c`in the deflected frame lie on the line CD in the original frame?
 

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Ashu2912 said:
This is a diagram I found in "Structural Analysis" by Aslam Kassimalli. Here, if the member AC is inextensible, shouldn't the point c`in the deflected frame lie on the line CD in the original frame?
I don't think so. I think that all that is required for AC to be inextensible is that the cumulative length along the line AC be the same as in the original frame.

Chet
 
Ashu2912 said:
In analysis of frames, we say that "The members of the frames are axially inextensible". In context of frames with vertical legs, what I understand is that the length of the chord joining the member ends in the displaced condition would be same in the axial direction. However, what does it imply in frames with inclined legs?
" The members of the frames are axially inextensible". does that mean no axial deformation? Doesnt seem to be right..
 
lingesh said:
" The members of the frames are axially inextensible". does that mean no axial deformation? Doesnt seem to be right..
Pretty much.

All you've provided is a diagram. Is it being used in your text to help explain a certain mechanics topic, by chance?

Often, in explaining a certain point of mechanics or whatever, a simplified model is used initially to explain the concept. Once enough concepts are understood by the student, more complex (and more realistic) models can be analyzed and discussed in more complete detail.
 

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