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

[ARNAR]

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??

 

[IFRs]

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

 

[ARNAR]

PLEASE FIND THE ATTACHED FILE

 

[ARNAR]

@ IFRS : The section properties are almost same in both cases. you can find in the attached file

 

[hokie66]

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

 

[ARNAR]

@ 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 )

 

[hokie66]

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.

 

[LittleInch]

The beams are very different.

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

 

[rb1957]

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 ?

 

[patswfc]

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.

 

[patswfc]

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

 

[rb1957]

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 ?

 

[oldestguy]

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