Does This Flexural Stress Equation Apply to Different Beam Conditions?

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Discussion Overview

The discussion revolves around the applicability of a specific flexural stress equation for beams with different conditions, particularly focusing on rectangular cross sections. Participants explore the validity of the equation under various scenarios, including different beam types and load applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents the equation for calculating flexural stress as 3PL/2Bd² and questions its applicability to both filled and dull beams.
  • Another participant clarifies that the equation is specific to a solid horizontal rectangular beam of negligible weight, supported at both ends, with a concentrated load applied at its midpoint.
  • A participant seeks clarification on the meaning of the terms in the equation My/I, asking for definitions of the variables involved.
  • Further clarification is provided regarding the variables, with M representing the bending moment, y the distance from the neutral axis, and I the Area Moment of Inertia. The maximum moment is noted to occur at the midpoint.
  • A participant shares their background, indicating they are relearning physics and seeking to advance their knowledge in structural engineering.
  • There is a suggestion that the original poster should provide their work for more precise assistance, indicating a preference for structured inquiry.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the flexural stress equation under various conditions, with no consensus reached on its validity across different beam types and load applications.

Contextual Notes

Limitations include the specific conditions under which the flexural stress equation is valid, as well as the assumptions regarding beam weight and support conditions. The discussion does not resolve the applicability of the equation to all scenarios mentioned.

Who May Find This Useful

This discussion may be of interest to students and professionals in structural engineering, physics, and related fields who are exploring the principles of beam mechanics and flexural stress calculations.

Aragorn49
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From what I know the equation for calculating flexural stress of a beam with a rectangular cross section is:

3PL/2Bd2

I have two questions about the validity of this equation. I will post a pic I just made to show what I mean:

1st question, Does this equation work both for filled beams (A,) and dull beams (B,)?

2nd question, Does this equation work both for when the force is applied in the exact center of the beam (C,) and for when the force is applied to the edge of the middle area (D,)?

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The equation you listed applies only to a solid horizontal rectangular beam of negligible weight and of length L and pin supported at each end, with a concentrated load P applied at its midpoint. You don't want to blindly apply equations. In general, the flexural stress in beam at a given point is My/I.
 
Thank you for the help. But what does My/I mean? What quantities do the letters of that equation represent?
 
I believe you posted on the wrong forum, since this does not appear to be a homework problem. M is the bending moment, y is the distance from the neutral axis, and I is the Area Moment of Inertia. For the beam in discussion, the max moment M occurs at mid point = PL/4, the moment of inertia I is bd^3/12, and the max stress at this section occurs at the outer fibers where y = d/2. Sound at all familiar?

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I apologize if I posted on the wrong forum, I'm new here. It isn't exactly a homework problem, more like going a bit ahead of the stuff I learn right now. After I finished high school I had a few free years and now I want to get my physics knowledge back in shape cause I want to go studying structural engineering on a university. I forgot much of my high school knowledge so I'm pretty much relearning it right now, though sometimes I get the diesire to learn some more advanced stuff which really interests me.

Btw, where is the section where questions like these should be posted?

Thank you for your time
Aragorn49
 
Oh no problem, I just didn't want to give you a precise answer without you showing your work if this was in fact a homework question.

In the future for questions along these lines, you can post under Engineering/General Engineering. Thanks.
 

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