Question

A concrete highway is built of slabs of 14 m long (20°C). How wide should the expansion cracks be (at 20°C) between the slabs to prevent buckling if the range of temperature is from -30°C to 50°C?

Answer 1

I know the equation is
\[\Delta L = \alpha L \Delta T\]

Answer 2

is the ΔT 80°C? or is it 30°C?

Answer 3

\[\Delta T\]is the difference in the temperature from the initial temp. (20C here) to the final temp.

Answer 4

\[\Delta T=\text{max temp change}\\
\Delta T_1=T_{\rm final}-T_{\rm initial}=50-(20)=30^\circ C\\
\Delta T_2=T_{\rm final}-T_{\rm initial}=-30-(20)=-50^\circ C
\]

Answer 5

cracks should withstand both the temperature changes.

Answer 6

i think we should only worry about the expansion. so the change in length due to the increase from the initial temperature should be taken care of...