How Do You Calculate Stress at Different Points in a Loaded Beam?

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SUMMARY

The discussion centers on calculating stress at different points in a loaded beam, specifically addressing the impact of point loads and the application of Saint Venant's principle. Participants clarify that while axial loads produce uniform stress across the cross-section, bending moments and the location of the load can lead to varying stress levels, particularly at points away from the centroid. The centroid of a square cross-section is confirmed to be at its center, and the need to consider bending moments when analyzing stress distribution is emphasized.

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  • Understanding of stress calculations, specifically σ = P/A
  • Familiarity with Saint Venant's principle in mechanics
  • Knowledge of centroid location determination in geometric shapes
  • Basic concepts of bending moments in structural analysis
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  • Study the application of Saint Venant's principle in beam theory
  • Learn about calculating bending moments in loaded beams
  • Explore methods for determining centroids of various geometric shapes
  • Investigate stress distribution in prismatic members under axial and bending loads
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Mechanical engineers, civil engineers, and students studying structural analysis who are looking to deepen their understanding of stress calculations in loaded beams.

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"see attachment"Normally I would assume that the stress caused by the point load at A is equal to σ=P/Area. however since there is a distance between the two points and because of Saint Venants principle, I don't think that the stress at A will be the same with the stress at D. In order to find the stress at D, do I have to find the centroid or the moment? (using this equation σ=((-My)/I) ) or angle of twist??
 

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Well, the attachment is not totally clear on the position of A, but let's assume that the force at A is applied at the center of the cross-section.

Why would you assume that a centrally loaded member has developed a bending moment?

What is it about this problem which makes you think St. Venant's principle applies?

You've got a prismatic member with a square cross-section. Can't you identify the location of the centroid without calculation?
 
I don't think that there will be any moment in the center load. (Can I assume that the stress will be exactly the same for the entire rectangle?)

For the St. Venants principle, I think it is there because point D is on the side of the rectangle, i doubt that it will experience the same stress as that of the centre of the rectangle.

The centroid should be in the centre of the rectangle.
 
Junkwisch said:
I don't think that there will be any moment in the center load. (Can I assume that the stress will be exactly the same for the entire rectangle?)

For the St. Venants principle, I think it is there because point D is on the side of the rectangle, i doubt that it will experience the same stress as that of the centre of the rectangle.

The centroid should be in the centre of the rectangle.

Well, axial loads are assumed to produce the same stress over the entire cross-section. After all, that's what σ = P/A means.
 
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