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A concrete highway is built of slabs 18.0 m long (at 25 °C). How wide should the expansion cracks be (at 25 °C) between the slabs to prevent buckling if the annual extreme temperatures are −32 °C and 52 °C?(the coefficient of linear expansion of concrete is 1.20 × 10 − 5 °C-1) g

Respuesta :

To solve the problem it is necessary to apply the concepts related to thermal expansion of solids. Thermodynamically the expansion is given by

[tex]\Delta L = L_0 \alpha \Delta T[/tex]

Where,

[tex]L_0 =[/tex] Original Length of the bar

[tex]\Delta T[/tex]= Change in temperature

[tex]\alpha[/tex]= Coefficient of thermal expansion

On the other hand our values are given as,

[tex]L_0 = 18m[/tex]

[tex]\alpha = 12*10^{-6}/\°C[/tex]

[tex]T_2 = 52\°C[/tex]

[tex]T_1= 25\°C[/tex]

Replacing we have,

[tex]\Delta L = L_0 \alpha (T_2-T_1)[/tex]

[tex]\Delta L = (18)(12*10^{-6})(52-25)[/tex]

[tex]\Delta L = 5.832*10^{-3}m[/tex]

The width of the expansion of the cracks between the slabs is 0.5832cm

The width of the expansion cracks between the slabs to prevent buckling should be 0.5832cm.

How to calculate width?

According to this question, the following information are given:

  • Lo = Original length of the bar
  • ∆T = Change in temperature
  • α = Coefficient of thermal energy

The values are given as follows:

  • Lo = 18m
  • T1 = 25°C, T2 = 52°C
  • α = 12 × 10-⁶/°C

∆L = Loα (T2 - T1)

∆L = 18 × 12 × 10-⁶ (27)

∆L = 3.24 × 10-⁴ × 18

∆L = 5.832 × 10-³m

Therefore, the width of the expansion of the cracks between the slabs is 0.5832cm.

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