#### MiguelPenaWSE

##### Structural

- Sep 2, 2013

- 29

I'd like some assistance with Excel.

I'm designing a prestressed I Girder.

I'm trying to equate two equations to solve for two unknowns in excell.

The equations are.

-(P/A) + (P x e / Stop ) - (Mmin / Stop) <= Limit @ top

-(P/A) - (P x e / Sbot ) + (Mmin / Sbot) <= Lmit @ bottom

Stop = 216,600,000 mm3

Sbot = 220,200,000 mm3

A = 499,000 mm2

Mmin = 922,000,000 N-mm

Limit @ top = 1.369 MPa

Limit @ bot = 18.0 MPa

P = prestressing force in tendon

e = eccentricity at mid span

I've solved it by hand twice. Please see below

Trial #1

P = 4,189,263 N

e = 725 mm

Trial#2

P = 4,866,760 N

e = 184 mm

I'd like to know how to write these equations in excel so I can get an accurate answer for both unknowns.

I saw a few threads similar to this one but in those there was only one unknown per fraction... In my case I have two unknowns in one franction (P x e / S).

I appreciate your help.

Thanks