Question

You are given the job of designing a bridge that is to be made of concrete slabs that rest on a steel support frame. The total length of the bridge is 306 m, and you want to be sure that the expansion joints are sufficiently large. If the temperature increases by 22

Answer 1

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You are given the job of designing a bridge that is to be made of concrete slabs that rest on a steel support frame. The total length of the bridge is 300 m. and you want to be sure that the expansion joints are sufficiently large. If the temperature increases by 25 deg.C., what is the difference in the new lengths of the concrete and steel components of the bridge? Which of these components will have the largest increase in length?

answer

The length of the bridge is L = 300 m
The raise in temperature dT = 25 C

Coefficient of linear expansion of steel = 11*10^-6 /C
Coefficient of linear expansion of concrete = 12*10^-6 /C

The increase in length of the steel portion is

dL = (coefficient of linear expansion of steel)LdT
dL = 11*10^-6 * 300 * 25
dL = 0.0825 m
dL = 82.5 mm

The increase in length of the concrete portion is

dL = (coefficient of linear expansion of concrete)LdT
dL = 12*10^-6 * 300 * 25
dL = 0.09 m
dL = 90 mm

Concrete will have larger increase in length compared to that of the steel