Beam Analysis


I am having a problem with analyzing a beam constructed with millboard (a sheet of bristol-board type wood). The millboard is used to construct an "I-Beam" with multiple vertical "I"s. The cross-section is something like:

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The problem is that the Modulus of Elasticity/Young's Modulus is much higher in tension than in compression. I am not sure how this affects the determination of the Neutral Axis (the axis where there is no Normal Stress). If E were the same in tension and compression, the Neutral Axis would just be located along the centroid of the cross-section. Does anyone have any ideas of how this type of beam can be analyzed for Normal Stress?

Thanks, Nish

Systems Design Engineering, University of Waterloo

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Loading thread data ... wrote in news:1142316523.765966.172090

Well, now, I wonder how 'they' design steel reinforced concrete beams? The assumption there is that concrete has no stiffness in tension. And obviously the steel has a different E to the concrete

You need to know the following three things:

the strain will be proportional to the distance from the neutral axis

the neutral axis will move.

there will be no net axial force in a section.


Greg Locock

Reply to
Greg Locock

Why is that? Are the pieces not glued or bonded?

Analyze it like a sheet-stringer or sandwich design. The "face sheets" react the axial and moments and the "Is" react shears.

Reply to
Jeff Finlayson

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