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# I beam strength formula

## I beam strength formula

(OP)
Is there a simple formula to find out how much uniform weight an I beam can support. example type in the size of the beam (W8)and the span (24ft)and come up with the lbs it can support (if supported on the ends).

### RE: I beam strength formula

Considering only flexural stress of the steel beam, you can derive an equation for uniform load w from these equations:

M = Fb S
M = w L^2 / 8

solving for w,

w = 8 Fb S / L^2
where Fb is the allowable bending stress

There isn't one single simple formula for obtaining the maximum uniform load a beam can support as it depends on the support conditions.  In addition, flexural stress may not be the controlling factor since for long spans, beam deflection usually controls.

Invest in a relatively inexpensive steel beam program called RAMSBeam from http://www.ramint.com/products/r_sbeam.jsp

### RE: I beam strength formula

You should be looking for a professional.  There are more things to do than simply sticking numbers in an equation.  You have to know which numbers, where they go, and which equations to check.

### RE: I beam strength formula

I second what UcfSE stated. There are many considerations beyond just bending stress level for instance acceptable deflection, lateral bracing, shear, connections, etc.

### RE: I beam strength formula

I agree with UcfSE and jike.  Deflection would be a huge concern for me with a W8 spanning 24 feet, even if braced and properly connected.

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