Calculating Reactions and Bending Moments for Fixed End Beam

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Discussion Overview

The discussion revolves around calculating reactions and bending moments for a fixed end beam subjected to two point loads. Participants are addressing a homework problem that involves determining the support reactions (Ra, Rb) and moments (Ma, Mb) at the ends of the beam, with a focus on the methods and calculations involved.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents initial calculations for Ra, suggesting a value of 40.52511, but expresses uncertainty regarding Rb, with conflicting results of 32.06 and 57.57.
  • Another participant emphasizes the need to determine support reactions before calculating bending moments and requests clarification on the beam's configuration, specifically the location of point A.
  • A third participant assumes the beam is fixed at both ends and notes that the sum of Ra and Rb should equal 98.1, indicating a potential issue if this is not the case.
  • This participant also inquires about the original poster's background in indeterminate structures and suggests consulting structural analysis textbooks for further guidance.
  • A fourth participant provides a link to a resource with formulas for different loading and boundary conditions, suggesting that practical engineers often seek direct answers rather than detailed calculations.
  • This participant also advises the original poster to refer to their teacher's notes and a good textbook if the problem is for a course assignment.

Areas of Agreement / Disagreement

There is no consensus on the correct values for Ra, Rb, Ma, or Mb, as participants express differing opinions and calculations. The discussion remains unresolved with multiple competing views on the approach to solving the problem.

Contextual Notes

Participants note the importance of providing a free body diagram and detailed calculations to clarify the problem. There is an acknowledgment of the need for foundational knowledge in structural analysis and strength of materials, which may affect the ability to solve the problem accurately.

bakoo
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Homework Statement



Fixed end beam with

Length = 1m
Load 1 = 58.86n @ 0.4m from A
Load 2 = 39.24n @ 0.85m from A

Find Ma, Mb, Ra, Rb


Homework Equations



Not Sure, where help is needed


The Attempt at a Solution



Well i think, almost sure from 2 methods that Ra = 40.52511

I have tried to calculate Rb but keep getting different answers, so far i have got

Rb = 32.06 and Rb = 57.57

I think Ma is -9.22, but not 100%. Keep getting different answers for Mb, 9,903 and Mb 2.7 and Mb
 
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To find the bending moments, you need the support reactions first, then you need to cut the beam into pieces, and then sum the moments independently, from the first whole piece.

Can you please provide more information for this question, such as, where is A, is A the fixed end, or the open end? Providing a free body diagram of what you done would be helpful too.
 
Since the Moments and reactions of both ends are required, I assume that the beam is fixed at both ends. Could you please confirm?
At this point, if the sum or Ra and Rb is not 98.1, you are in trouble.

Before we go further, may I enquire if you have already done some work on indeterminate structures? It will be first year university in engineering or equivalent, or higher. What have you learned so far from the course. Do you have textbooks on structural analysis, such as "Theory of Structures" by Stephen Timoshenko,
https://www.amazon.com/dp/0070648689/?tag=pfamazon01-20
This book is sure to be found in all university libraries. You could use any other ones.

On second thought, if you have done Strength of Materials, you might have the tools required to solve the problem analytically.

How did you get your Ma and Mb. Could you post your calculations, even if you think they may be wrong?
 
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If you only need an answer as most practising engineers do, the following link gives the formulae for different loading and boundary conditions:
http://www3.hi.is/~thorstur/teaching/cont/Continuum_CommonBeamFormulas.pdf

As it is a .pdf file, the display of the page will take some time (a couple of minutes).

If you are doing the problem for a course, I suggest you work on your teacher's notes supplemented by a good textbook.

Feel free to post questions after you have studied the subject.
 
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