To relieve a load-bearing wall, I will use a steel beam. Calculations show that a beam with at least a moment of inertia Ixx = 3000cm3 is required. I am now considering an I220 beam due to its relatively low weight (31.1kg/m) compared to an HEB or HEA. It seems like most people choose HEA or HEB beams, is there any good reason for this? The closest is HEB180 but with a weight of 51.2kg/m, since the beam is 4.5m long, there will be a noticeable difference in total weight. The H-beams provide a slightly lower building height but are wider, are there any other advantages or disadvantages??
Since an I-beam has narrower flanges than HE-A, -B, and -M, if greater support is needed, it is better to choose one of the latter, especially if the support is small on the lower flange in towards the web.
With a high height on an I-beam and long span, one must also consider web buckling. It is less in the HE series than in an INP or IPE beam.
The sought Wx means the same thing, but the weight is derived from thicker flanges, often with the same web thickness. This is because the flanges handle the moment during bending and challenge the material's strength. The web basically serves only as a spacer to keep the flanges the same distance apart.
With really large loads (alternatively span, or both), the allowed stress is lower in a thicker material of the same quality than in a thinner one. In other words, the result is a larger Wx. This would suggest a thinner INP or IPE profile, but then you are guaranteed to have to weld on supports (transverse bars between the flanges) against web buckling and tipping, which makes the finished beam more expensive than with the corresponding Wx from the HE series.
Addition:
The bending resistance is denoted Wx and Wy depending on the direction referred to.
The unit is cm^3
Ix and Iy denote the moment of inertia, which is something completely different.
The unit is cm^4
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Byggaren
With a high height on an I-beam and long span, one must also consider web buckling. It is less in the HE series than in an INP or IPE beam.
The sought Wx means the same thing, but the weight is derived from thicker flanges, often with the same web thickness. This is because the flanges handle the moment during bending and challenge the material's strength. The web basically serves only as a spacer to keep the flanges the same distance apart.
With really large loads (alternatively span, or both), the allowed stress is lower in a thicker material of the same quality than in a thinner one. In other words, the result is a larger Wx. This would suggest a thinner INP or IPE profile, but then you are guaranteed to have to weld on supports (transverse bars between the flanges) against web buckling and tipping, which makes the finished beam more expensive than with the corresponding Wx from the HE series.
Addition:
The bending resistance is denoted Wx and Wy depending on the direction referred to.
The unit is cm^3
Ix and Iy denote the moment of inertia, which is something completely different.
The unit is cm^4
_______________________
Byggaren
Last edited by a moderator:
hebbe said:To relieve a load-bearing wall, I will use a steel beam.
Calculations show that a beam with at least a bending resistance Ixx = 3000cm3 is required.
I'm considering an I220 beam due to its relatively low weight (31.1kg/m) compared to an HEB or HEA.
It seems like most people choose HEA or HEB beams, is there any good reason for this?
The closest is HEB180 but with a weight of 51.2kg/m, since the beam is 4.5m long, there is a certain difference in total weight.
H-beams indeed provide a slightly lower construction height but are wider, are there any other advantages or disadvantages??
You might need to check your calculation again. An IPE-220 or INP-220 has Wx around 252-278 cm^3.
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The Builder
My mistake, it should of course be 3000cm^4.
It is Ixx that is used when calculating deflection, and there shouldn't be high shear stresses.
Load case:
Total load 54000N
Deflection:
5*Q*L^3/384EI = 5*54000*4.7^3/384*210*^9*3000*10^-8 = 0.0115m
That is approximately 10mm (<L/300 ok!)
It is Ixx that is used when calculating deflection, and there shouldn't be high shear stresses.
Load case:
Total load 54000N
Deflection:
5*Q*L^3/384EI = 5*54000*4.7^3/384*210*^9*3000*10^-8 = 0.0115m
That is approximately 10mm (<L/300 ok!)
You don't calculate the beam's bearing capacity that way. If it's a beam on two supports (simply supported) loaded with a uniformly distributed load, the formula is: Mmax=qxl^2/8 (and nothing else). Then you divide Mmax by the allowable stress and obtain Wx, i.e., the required bending resistance = profile.hebbe said:
However, you check the deflection afterward with the formula you provide, and it can be at most L/400, not 300. If it becomes larger, you need to move up one step higher on Wx.
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Byggaren
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