What does Young's Modulus x 2nd Moment of Area Equal

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Discussion Overview

The discussion revolves around calculating the relative stiffness of I beams using Young's Modulus and the second moment of area, particularly in the context of a frame and moment distribution method. Participants seek clarification on the necessary calculations and parameters involved.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant suggests that multiplying Young's Modulus by the second moment of area is sufficient for determining relative stiffness, questioning if this approach is correct given the context of relative units.
  • Another participant inquires whether the beam length should also be considered in the calculations.
  • A different participant points out the need for more specific information regarding the problem, emphasizing that the stiffness of a beam is typically determined by its moment of inertia and referring to the product EI as 'bending stiffness' or 'flexural rigidity.'
  • A participant describes a more complex problem involving a frame and the moment distribution method, indicating the need to find the force that will cause the first yield in the frame and expressing the importance of calculating the relative flexural rigidity of the beams.
  • One participant requests a figure related to the problem to aid in understanding.
  • Another participant reiterates the complexity of the frame problem and asks for standard tables that provide the second moment of area for the specified British sections of the beams and columns.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the calculations required for determining relative stiffness, and multiple viewpoints regarding the necessary parameters remain present.

Contextual Notes

The discussion lacks specific assumptions about the application of the calculations, and there is uncertainty regarding the inclusion of beam length in the stiffness determination. Additionally, the need for standard tables for the second moment of area is mentioned but not resolved.

kiteboy
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Hi all

I need to find the relative stiffnes of certain I beams from here

http://tsbluebook.steel-sci.org/EN/Browsers/Main.htm

Im assuming all I need to do times the Youngs Modulus by the 2nd Moment of Area

In my head I am making it more complicated than it should be so I hope this is all it is

As its all relative units etc don't matter - would that be correct??

Thanks for any info too
 
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Will I also have to divide by the beam length too??
 
Your post is a little vague. Is there a problem associated with your question? It would help if you could post as much information as you can.

In general, the stiffness of a beam in resisting bending is usually determined by its moment of inertia, or the second moment of area. The quantity EI is also called the 'bending stiffness' or the 'flexural rigidity'.
 
There is a problem regarding a frame and the moment distribution method and I need to find the force that that will cause first yield to take place on the fram. It seems a bit involved to put the whole question here so thought Id ask a basic question and the first I think is to get the relative flextural rigidity of the beams of the frames

the beams for example are the following sizes

It is made from structural steel sections of mild steel as follows:
Column AB: universal column section 203x203x60, see section b-b for orientation.
Beam BC: universal beam section 406x178x74, see section a-a for orientation
Column CD: universal column section 254x254x89, see section b-b for orientation

So to start the calcs off and moment distribution the relative stiffness is needed hence me asking the above - sorry if vaugue
 
Apparently, there is some sort of figure associated with this problem. Can you post it?
 
These
kiteboy said:
There is a problem regarding a frame and the moment distribution method and I need to find the force that that will cause first yield to take place on the fram. It seems a bit involved to put the whole question here so thought Id ask a basic question and the first I think is to get the relative flextural rigidity of the beams of the frames

the beams for example are the following sizes

It is made from structural steel sections of mild steel as follows:
Column AB: universal column section 203x203x60, see section b-b for orientation.
Beam BC: universal beam section 406x178x74, see section a-a for orientation
Column CD: universal column section 254x254x89, see section b-b for orientation

So to start the calcs off and moment distribution the relative stiffness is needed hence me asking the above - sorry if vaugue
These are british sections. Do you have standard tables giving you the 2nd M of A for each one?
 

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