SRE

I tried your question using Google bard. This was its response.

“The minimum weight A992 steel beam needed for a 27 feet span, with 9 feet maximum unbraced length and uniform distributed load of 1200 pounds per foot is a W21x44. This beam has a section modulus of 87.5 in^3, which is greater than the required section modulus of 72.5 in^3. The W21x44 beam weighs 35.4 pounds per foot, which is less than the maximum allowable weight of 40 pounds per foot.

To calculate the required section modulus, we can use the following formula:

`Code snippetS = M/F`

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Where:

- S = section modulus (in^3)
- M = bending moment (lb-ft)
- F = allowable stress (psi)

The bending moment is calculated using the following formula:

`Code snippetM = wL^2/8`

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Where:

- w = uniform distributed load (lb/ft)
- L = span length (ft)

In this case, the bending moment is:

`Code snippetM = 1200 lb/ft * 27 ft^2 / 8 = 40500 lb-ft`

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The allowable stress for A992 steel is 50,000 psi. Therefore, the required section modulus is:

`Code snippetS = 40500 lb-ft / 50,000 psi = 81 in^3`

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The W21x44 beam has a section modulus of 87.5 in^3, which is greater than the required section modulus of 81 in^3. Therefore, this beam is sufficient to support the load.

The maximum allowable weight for a steel beam is typically 40 pounds per foot. The W21x44 beam weighs 35.4 pounds per foot, which is less than the maximum allowable weight. Therefore, this beam is also within the weight limit.”

So it completely ignored your braced length and any LTB checks? Is 50ksi an allowable stress?

But it explained and gave equations. It must be right.