Thermal Expansion, Young's Modulus

[pat666]

Homework Statement

6. A steel beam is used in the road bed of a bridge. The beam is mounted between two concrete supports when the temperature is 23⁰C, with no room for thermal expansion. What compressional stress must the concrete supports apply to each end of the beam, if they are to keep the beam from expanding when the temperature rises to 42⁰C?
Co-efficient of linear expansion for steel = 11 x 10-6K-1
Young’s modulus for steel = 210GN.m-2

Homework Equations

deltaL/L=alpha deltaT
F/A*=delta L/L*Y

The Attempt at a Solution

Ive found delta L/L to be 2.09*10^-4 I've also done about a thousand other things but everything i try needs an original length, i feel like I've overlooked a simple step or something... can someone please give me a hand.

 

[Stonebridge]

You don't need the original length if you have ΔL/L
Young's modulus= stress / (ΔL/L)
You are given the modulus and need to calculate stress.

 

[pat666]

ok i have never seen this formula is stress defined as force of force/unit area??

 

[Stonebridge]

ok i have never seen this formula is stress defined as force of force/unit area??

Yes, stress is force per unit cross section area = F/A
strain is extension per unit length = ΔL/L
Young's modulus is stress/strain

 

[pat666]

ok i remember that from an early lecture thanks

 

[marko_pl]

How/where can I find Young's Modulus for paper?