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3. A concrete highway is built of slabs 12 m long (20o C). How wide should the expansion cracks between the slabs be (at 20o C) to prevent buckling if the range of temperature is -30o to +50o C? ( = 12 x 10-6 oC-1 for concrete)

Respuesta :

Answer:

[tex]\Delta x=2.304\times 10^{-2}\ m=2.304\ cm[/tex] is the minimum gap between the slabs

Explanation:

Given:

  • length of the concrete highway, [tex]l=12\ m[/tex]
  • coefficient of thermal expansion, [tex]\alpha=12\times 10^{-6}\ ^{\circ}C^{-1}[/tex]
  • range of temperature variation, [tex](-30^{\circ}C\ to\ 50^{\circ}C) \Rightarrow \Delta T=80^{\circ}C[/tex]

Now form the equation of thermal expansion:

[tex]\Delta l=l\times \alpha\times \Delta T[/tex]

[tex]\Delta l=12\times (12\times 10^{-6})\times 80[/tex]

[tex]\Delta l=1.152\times 10^{-2}\ m[/tex]

Since each slab of the highway expands by the above length so the minimum gap between the slabs to prevent buckling:

[tex]\Delta x=2\times \Delta l[/tex]

[tex]\Delta x=2\times( 1.152\times 10^{-2})[/tex]

[tex]\Delta x=2.304\times 10^{-2}\ m=2.304\ cm[/tex] is the minimum gap between the slabs