Too close to maximum deflection or not too close to maximum deflection

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Discussion Overview

The discussion revolves around the calculation of beam deflections under uniform and point loads, specifically addressing concerns about being close to maximum deflection limits in a homework context. Participants explore the implications of these calculations in structural engineering.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant expresses concern about a calculated deflection being only .005" less than the maximum deflection, questioning whether this proximity might be viewed negatively by their professor.
  • Another participant reassures that being close to the maximum deflection is acceptable, noting that safety factors are still in place.
  • A third participant shares an anecdote about a frame manufacturer testing deflections, indicating that actual deflections can vary significantly from calculated values depending on construction factors.

Areas of Agreement / Disagreement

There appears to be a general reassurance regarding the calculated deflection being acceptable, though the discussion includes varying perspectives on how close is too close and the implications of actual versus calculated deflections.

Contextual Notes

The discussion does not resolve the question of how close is considered acceptable in structural engineering, and it highlights the variability in deflection outcomes based on construction methods.

Who May Find This Useful

Students in engineering courses, particularly those focused on structural analysis and design, as well as professionals interested in practical applications of deflection calculations.

yohnson
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Homework Statement


Calculating uniform and sometimes point loads on simple beams and the calculated beam deflections using ETLs (estimated tabular loads).

My question in simply if I have found a deflection that is .005" less than the given maximum deflection, is it so close that if I don't recalculate, will my professor think that I'm some kind of an engineering maverick/loose cannon? I'm not kidding, I seriously just don't want to be too close for comfort, and I don't know yet how close structural engineers like to get.


Homework Equations


ETL = [(M)(8)] / L

deflection = [(5)(ETL)(L3) / [(384)(E)(I)]


The Attempt at a Solution



Deflection found. too close?

actual deflection = .660" maximum deflection = .6666"
 
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If that is the maximum great, don't worry it is just fine, safety factors are still there.
 
thanks, Lok!
 
Just to put a perspective: A frame manufacturer I know tested a bare frame and got pretty much the calculated deflection. Then the other frames adjacent were built, and connected with purlins etc. Same test on original frame got about two thirds of the original deflection. Finally all the sheet cladding was added. Tested again, the deflection was about one third of the calculated deflection.
 
pongo38,
That makes sense, I'm so glad. I turn in my final project tomorrow!
Thanks!
 

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