Homework Help: Axial Deformation on Statically indeterminate beam

1. Nov 1, 2014

SteliosVas

1. The problem statement, all variables and given/known data

I am trying to find a solution to the below attached image.
The area for AB=CD = 0.8m^2
Area of BC = 0.3m^2

Force at B = 140 kN (left)
Force at C = 60 kN (right)

AB=CD = Concrete with a E of 25,000N/mm^2
CD = Steel with an E = 200,000N/mm^2

2. Relevant equations

PL/AE

3. The attempt at a solution

This is where I get confused because there is a force acting at B and a force acting at C I am not sure if I need to make a cut at say B or make a cut at C.

I understand the the sum of the forces in X direction have to equal Ax + Dx = 80 kN (As a result of 140 - 60 kN)

Now taking BC as the redundant section

PL/AE for section AB should that of section CD?

I am not sure if I am going about it the right way?

If it was one continuous section with forces only in one direction or even two I understand but because of that section BC it has thrown me out .

2. Nov 1, 2014

SteamKing

Staff Emeritus
There's no image attached to your post.

3. Nov 1, 2014

SteliosVas

Oops... Here we go

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4. Nov 1, 2014

SteliosVas

Second Attempt at solution

Taking Section AB

δA/D = Fab*L(ab)/AE = Fcd*L(cd)/AE

Now F in AB = 140 kN
and F in CD = -60 kN

*** Edit ***

My compatibility equation of Fab + Fcd = 80 kN?

Last edited: Nov 1, 2014