A square beam laid flat is then rotated in such a way that one of its...
Moment capacity of a beam is given by MR = σ
y × Z
For a particular beam σy is constant
∴ MR ∝ Z
When beam is laid flat, then
∴ Moment capacity increases by 41.4%.
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A square beam laid flat is then rotated in such a way that one of its...
Effect of rotation of square beam on moment capacity
Heading: Introduction
When a square beam is laid flat and rotated in such a way that one of its diagonals becomes horizontal, its moment capacity is affected. This effect can be calculated using mathematical formulas.
Heading: Calculation of moment capacity
The moment capacity of a square beam can be calculated using the formula M = fy(Zx + Zy)/gammaM, where M is the moment capacity, fy is the yield strength of the beam, Zx is the plastic section modulus about the x-axis, Zy is the plastic section modulus about the y-axis, and gammaM is the safety factor.
Heading: Calculation of plastic section moduli
The plastic section moduli Zx and Zy can be calculated using the formulas Zx = bh^2/6 and Zy = hb^2/6, where b and h are the width and height of the beam.
Heading: Effect of rotation on plastic section moduli
When the square beam is rotated in such a way that one of its diagonals becomes horizontal, its width and height change. The new width and height can be calculated using the formulas b' = h/sqrt(2) and h' = b/sqrt(2), where b' and h' are the new width and height.
Heading: Calculation of new plastic section moduli
Using the new width and height, the new plastic section moduli Zx' and Zy' can be calculated using the formulas Zx' = b'h'^2/6 and Zy' = h'b'^2/6.
Heading: Calculation of new moment capacity
Using the new plastic section moduli, the new moment capacity M' can be calculated using the formula M' = fy(Zx' + Zy')/gammaM.
Heading: Comparison of moment capacities
The ratio of the new moment capacity to the original moment capacity can be calculated as M'/M = (Zx' + Zy')/(Zx + Zy). Substituting the values, we get M'/M = (2 + sqrt(2))/2. This is approximately equal to 1.414, which represents an increase in moment capacity of 41.4%.
Conclusion
When a square beam is rotated in such a way that one of its diagonals becomes horizontal, its moment capacity increases by 41.4%.
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