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Dimension to neutral axis in beam calcs

Dimension to neutral axis in beam calcs

Dimension to neutral axis in beam calcs

I'm doing some strength calcs using beer and johnston's "mechanics of materials book.  I assume that the "c" dimension to the neutral axis of a beam in pure bending is taken from the side of the beam in compression.

is this correct?? My stresses come out much lower with it this way.

please advise...  
thanks in advance.


RE: Dimension to neutral axis in beam calcs

"c" should be the distance from your neutral axis to the "extreme fiber"

RE: Dimension to neutral axis in beam calcs

by "extreme fiber" you mean furthest from the neutral axis?

RE: Dimension to neutral axis in beam calcs

Sometimes the allowable compressive stress for a built up section (which I surmise is what you are describing) will be less than the allowable tensile stress.  Therefore, both values of "c" should be used to determine a compressive stress and a tensile stress.  If the allowable stresses are the same, then the greater value of "c" should be used, since this will give the greater bending stress.


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