Solve Beam with 3 Supports Problem

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Discussion Overview

The discussion revolves around a homework problem involving a beam supported at three points (A, B, and C) with a weight applied at a specific location. Participants explore methods to determine the reactions at the supports based on given parameters such as the weight, length of the beam, and distances between points.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the problem as statically indeterminate and suggests performing a deflection analysis by removing one support to calculate reactions and deflections.
  • Another participant expresses frustration about the complexity of the problem, indicating it is a task assigned by their new boss, which requires deriving a formula for practical application in their work.
  • There is mention of using Roark's formula and a paper from MIT, but the participant feels overwhelmed by the task and lacks sufficient knowledge to proceed.
  • A later reply questions the absence of a relevant table in Roark's reference material for this specific application, suggesting a potential oversight in the resources consulted.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to approach the problem, with differing views on the methods to be used and the resources available. The discussion remains unresolved regarding the best approach to solve the problem.

Contextual Notes

Participants express uncertainty about the appropriate equations and methods to apply, highlighting the problem's complexity and the need for further clarification on the assumptions involved in the analysis.

Who May Find This Useful

This discussion may be useful for mechanical engineering students or professionals dealing with statically indeterminate structures, particularly those seeking to understand deflection analysis and support reactions in beam problems.

Isimanica
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Homework Statement


Well this is the second time I have been given a problem that I just don't know what to do at work.
Simply put you have a beam that has 3 supports. A,B,C. With a weight at point w.
The goal I am told is to find all 3 points with just the the known of w (weight), L(length of beam), x (distance of point B from point A) and y (distance of weight from point A)

l-------L----------l
l---y---w
_______l_________
l------x---l--------l
A---------B-------C

Homework Equations


You got me. He said this would be easier than finding the weight of the support points on a piece of machinery.


The Attempt at a Solution


I tried using moments around point A and C but yeah that didn't work at all.
 
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The problem is statically indeterminate and you need to do a deflection analysis with one of the supports removed, calculate the deflection at that removed support, and reactions, then determine the force required at the removed support to give the negative of that deflection at the removed support such that the sum total of the deflection at that support is zero. Then use superposition to determine all reactions. Is this a Homework problem?
 
Oh no Jay this is my New boss giving me a problem to figure out and then derive a formula or solution that I can put into excel so that when we get an inquiry about load points for our Isolators that we could if need be tell them which product would best suit their needs out of our product line. This requires one to either know the weight at each of the supports which will have isolators attached or that we determine it for them if they don't know. This is just driving me batty. I got Roark's formula and a MIT guys paper that discusses this but I am in way over my head. I still got 2 and a half years of my ME degree plan to finish.

PS the little diagram is what he has drawn for me on papaer as well. so you have as much information as I have.
 
I'm surprised that Roark does not include a table for this application. Did you look under "Continuous Beam - Two Unequal Spans - Concentrated Load At Any Point" ?
 

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