# Beam Design (max allowable force) - Help

## Homework Statement

Case:

-Simply supported beam with central load. L = 570cm
- I-Beam. Height = 15cm. Base = 15cm. Thickness = 1cm.
- Material = mild steel. Assuming E = 210GPa.
- Safety Factor = 1.5.
- F = 2000N.

With those information i had obtained the I = 16.56x10^6 mm^4.

Now i dont know how to calculate:
- the max allowable force before it fails.
- If F = 2000N, is it safe to use this beam.

Please help.

## Answers and Replies

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PhanthomJay
Science Advisor
Homework Helper
Gold Member
You will need to find the maximum bending moment in the beam as a function of F, then find the maximum bending stress under that maximum moment, using the maximum bending stress formula, which you should be familiar with. Now you must know the yield stress for the given material, which must be given to you, since such yield stresses depend on the type of mild steel you are using. Apply safety factor appropriately, watch units, and solve for the allowable load F.

Dear PhantomJay....i am totally lost with your solution...would you please explain further..

Actually this is not my homework..my company wants to design a gantry and they want me to calculate the maximum allowable force for the beam.

Thanx again..

nvn
Science Advisor
Homework Helper
You could assume tensile yield strength, Sty = 235 MPa. Then you could say the maximum allowable midspan point load is F = 21.0 kN.

By the way, its.me.lah, always leave a space between a numeric value and its following unit symbol. E.g., 2000 N, not 2000N. See the international standard for writing units (ISO 31-0).