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Hello-

This isn't a homework problem, but a real life problem. I'm trying to size a beam for a set of stairs that I'm trying to design. I have some material picked out, and it looks strong enough, but when I try to run some numbers to confirm, they don't appear to match what I've experienced in the real world.

Calculate the maximum deflection of a simply supported beam given the following:

Total length: 27 feet

Material: Steel (E=30x10^6 lb/in^2

Cross section: See image

Weight: 0.283 lb/in^3

Maximum deflection of uniformly loaded simply supported beam (from Schaum's Outline Series, Strength of Materials 2/ed, P.161)

y=5/384 * wL^4/EI

Using the given above, along with the following:

w = 104.107 lb/ft

I = 23.05 in^4

Using the maximum deflection equation from above solving for y yields:

y=259.23 inches

This means that the middle of the beam will deflect almost 260 inches due to it's own weight?? I must be doing something wrong.....any help would be appreciated.

Thanks.

http://www.dom2.com/stairs/images/beam-x-section.jpg [Broken]

This isn't a homework problem, but a real life problem. I'm trying to size a beam for a set of stairs that I'm trying to design. I have some material picked out, and it looks strong enough, but when I try to run some numbers to confirm, they don't appear to match what I've experienced in the real world.

## Homework Statement

Calculate the maximum deflection of a simply supported beam given the following:

Total length: 27 feet

Material: Steel (E=30x10^6 lb/in^2

Cross section: See image

Weight: 0.283 lb/in^3

## Homework Equations

Maximum deflection of uniformly loaded simply supported beam (from Schaum's Outline Series, Strength of Materials 2/ed, P.161)

y=5/384 * wL^4/EI

## The Attempt at a Solution

Using the given above, along with the following:

w = 104.107 lb/ft

I = 23.05 in^4

Using the maximum deflection equation from above solving for y yields:

y=259.23 inches

This means that the middle of the beam will deflect almost 260 inches due to it's own weight?? I must be doing something wrong.....any help would be appreciated.

Thanks.

http://www.dom2.com/stairs/images/beam-x-section.jpg [Broken]

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