Simple bending moment calculation

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Discussion Overview

The discussion revolves around calculating the maximum bending moment for a beam based on a provided diagram. Participants are addressing the reactions at the supports and the overall loading system, with a focus on the technical aspects of bending moment calculations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about their calculations for the reactions at the supports, providing specific values based on their understanding.
  • Another participant suggests that the beam may tip over under the current loading conditions and requests a clearer sketch of the mechanical assembly to better understand the loading system.
  • Multiple participants challenge the correctness of the initial reaction calculations, providing their own calculations and suggesting that the reactions should be reconsidered based on equilibrium equations.
  • There is a recommendation to draw shear and moment diagrams to aid in the analysis of the bending moments.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correctness of the initial reaction calculations. There are competing views on the appropriate approach to determining the bending moments, indicating that the discussion remains unresolved.

Contextual Notes

There are limitations in the provided information, including potential missing assumptions about the loading conditions and the mechanical assembly. The calculations presented by participants depend on their interpretations of the diagram, which has not been fully clarified.

Wilson123
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Hi,

Really need some help with figuring out the max bending moment in the diagram shown below (I'm aware this is extremely simple but time and stress appear to have the better of me, so any help is appreciated)

upload_2017-3-10_21-32-47.png


I think I've worked out the reactions at each support by doing m=wL as the following

0.785 x 0.08 = 0.63
0.785 x 0.28 = 0.22

I'm also aware that I could be completely wrong with what I've just put above.

SOS
 
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The beam would probably just tip over with the forces acting in the directions shown .

We need to understand the actual loading system more clearly before calculating bending moments .

Can you post a sketch showing the actual mechanical assembly that your line drawing represents ?
 
I don't think the reactions are correct. As drawn, ΣM = 0 = 0.2R + 0.785(0.08) : R = - 0.314 kN : The "-" sign simply implies you have the right reaction, R, acting the opposite direction. ΣF = 0 = - 0.785 - 0.314 + L : The left reaction, L = 1.099 kN : Given the reactions you should be able to calculate the moment.
Draw shear and moment diagrams.
 
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Vector1962 said:
I don't think the reactions are correct. As drawn, ΣM = 0 = 0.2R + 0.785(0.08) : R = - 0.314 kN : The "-" sign simply implies you have the right reaction, R, acting the opposite direction. ΣF = 0 = - 0.785 - 0.314 + L : The left reaction, L = 1.099 kN : Given the reactions you should be able to calculate the moment.
Draw shear and moment diagrams.

Thanks a lot for your help.
 
Draw a shear diagram first.
 

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