Beam Bending Stress Calculation

And if it were 3 mtrs from the ground, what would the bending stress be?

The mixed-bag units are really great, too.

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Just reduce the elevation of the beam by .01 furlongs.

That's too easy; when the whole thing sits on the ground, the bending stress will be zilch.

But it negates the need to do any of those pesky calculations.

This question posed by the OP smacks of the typical student homework problem.

Why are there a mix of metric and US Empirical system units given in the first place?

First, the OP must use one system of unit measurement (and like terms), not both.

2nd, The OP must find or determine what the Section Modulus of this metric beam is........in mm^3 or in.^3, depending on the system being utilized. The Section Modulus is needed to determine the Design Bending Stress (fb) and compare it to the Allowable Bending Stress (Fb).....remember, there are two axis....the strong axis for I-beams is typically about the x-x axis, whereas the weak axis is bending and loading about the y-y axis. You need to know how the beam is oriented in relation to the the loading!

Maximum Bending Moment (Mx or My) (for simply support beam w/ single concentrated point load at midspan) = P * L / 4. Is US, the units would result in in-pounds, inch-Kips, Ft.-pounds, or inch-kips. A Kip = 1000 pounds.

Maximum Design Bending Stress (fbx) = Max. Mx / Sx.

Maximum Design Bending Stress (fby) = Max. My / Sy.

Either one is compared to to the Allowable Bending Stress, and here you need to know your steel code (like AISC) throughout to make a determination of what the value is....there are many factors involved, including but not limited to: unbraced lengths along the beam, if known or provided) and the orientation of the secondary framing or if it is continuously braced along the compression flange; The Yield Stress (Fy); etc etc etc etc which I will not go into any further here for brevity sake......

Personally, as a former professor I'd give you an F grade if you were my student! This is basic Static & Strength of Materials material that you should know inside and out, and upside down. LEARN IT by cracking open your assigned TEXTBOOK!

This is REALITY TIME....either you learn it now or you'll never become an engineer....or at least you'll be labelled a piss poor engineer.

Harsh yes, but life is harsh. Get with the program kiddo......

Thanks r8flex