Equivalent length of of column ?

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Discussion Overview

The discussion centers around the calculation of the load that a mild steel column can safely support, specifically focusing on the concept of equivalent length of the column. Participants explore the implications of missing information, such as the column's length and boundary conditions, in the context of applying Rankine's formula and other relevant equations.

Discussion Character

  • Homework-related
  • Debate/contested
  • Technical explanation

Main Points Raised

  • The original poster questions how to determine the equivalent length of the column without a specified length in the problem statement.
  • One participant suggests that without a given length, it may be possible to treat the equivalent length as a variable and express the load as a function of this variable.
  • Another participant mentions that their tutor indicated a length may not be necessary for short columns, raising the possibility of using a different formula.
  • There is contention regarding whether short columns require a length and boundary conditions, with some asserting that they do.
  • One participant proposes that the problem may simply be asking for the squash load using the formula f=P/A, questioning the relevance of Rankine's formula.
  • The original poster acknowledges the need for clarification on the problem's requirements and expresses uncertainty about the appropriate formula to use.

Areas of Agreement / Disagreement

Participants generally disagree on whether a length is necessary for short columns and the applicability of Rankine's formula. The discussion remains unresolved regarding the correct approach to the problem.

Contextual Notes

Participants note the absence of specific information regarding the column's length and boundary conditions, which are critical for applying the relevant formulas accurately.

rad10k
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Equivalent length of of column ??

Homework Statement



A Mild steel column has a cross section of 100 mm by 50 mm . Assuming a safety factor of 6 calculate the load that it can safely support?

Homework Equations



Rankines formula : W = Oc/K[1+a(AEe^2/I]


The Attempt at a Solution



My problem is with Ee = Equivalent length of column in millimetres

How do I find this value as the question does not give a length?

Thanks for any advice
 
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rad10k: I think you cannot solve this if no column length is given. You also need boundary conditions to be given. Are you sure no length is given? If you are sure no length is given, then perhaps the only thing you could do is, assume Ee is a variable, and obtain W as a function of Ee, which would be a curve.
 


Yes the question is an exact copy . I spoke to my tutor who informed me that I do not need a length for short columns so maybe I am trying to used the wrong formula for which Eulers formula also asks for Ee so I can't use that. The only other formula I know of is the straight line formula but for that you need to be given the end conditions ie. pin ends .
 
No, even short columns need a length, and boundary conditions. Something seems amiss.
 


Maybe all that is being asked for is the squash load from f=P/A. Who says that Rankine's formula is relevant?
 


Nobody I was just just going to use that. I think I need to go get clarification on what exactly the question is asking for. thanks
 

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