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REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

(OP)
Two beams with different sectional properties ( see the attached file. Fig 1 & fig 2 ) supported as simply supported at same span and same loading. While analyzing the section shown in fig 1 deflect more than Fig 2 . please help me to find a reason for that.

What are the sectional properties affect the deflection of a simply supported beam??

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

Look at the equations for beam deflection and you will find the section properties that are involved.

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

Ix of the two sections are different. Aside from anything else about those sections, Ix (moment of inertia) is the most important stiffness property.

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

(OP)
@ Hokie66 : Ix is torsional constant of the section . Z Axis is horizontal and Y axis is vertical.

IX = Torsional constant
IY = Moment of inertia about y-axis.(vertical )
IZ = Moment of inertia about z-axis (Horizontal )

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

OK, I had to put my glasses on to see the output. Strange nomenclature to me, but if that is the case, just insert Iz into my earlier comment in place of Ix.

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

The beams are very different.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

pray tell, which properties are "almost the same" ? I can't think of two more different sections !?

another day in paradise, or is paradise one day closer ?

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

Looks to me like Iz should be the vertical stiffness.
For the same span and loading the top beam should deflect(9984.6/5682.09) 1.76 times more than the lower beam.

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

rb1957, cant you see that the area is roughly the same! (only 6% difference) bigsmile

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

I wonder how this section properties program works ...
how does it figure out the thickness ? how to remove one enclosed area from the other ?
how does it work without a closed shape ? (and if it joins the last point to the first, then it'll get messed up, as both co-ords change)
and those torsion properties look really low ? do they account for the closed sections ??

another day in paradise, or is paradise one day closer ?

RE: REASON FOR MORE DEFLECTION ( SAME SUPPORT CONDITIONS, SPAN AND LOADING)

If this is a student question, check the rules here. Not allowed.

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