ZIMSEC O Level Combined Science Notes: Strength to Mass ratio
- Engineers do away with materials that are under little stress so as to be able to build efficient structures in terms of weight and cost
- The material that lies close to the neutral axis is under little stress
- Beams used in building should have a high strength to mass ratio
- The lower their mass the higher this ratio
- The diagram shows the cross section of different beams
- The hollow beams, the I and Z beams are just as strong as the solid beams
- But they are much lighter than their solid counterparts
- This is because unnecessary material has been removed in the hollow beams
- This results in a high mass to strength ratio
- In the Z and I beam the thin metal plates carries the shearing stresses.
- It holds the top and bottom plates together
- Also hollow box beams are used in constructions where light building materials are required
- For example win spans of bridges
- In I beams the middle of the beam resists vertical/shearing forces
- The flanges at the top and bottom of the beam resist horizontal tension and compression
- The horizontal compression and tension forces are often greater than the shear forces and are more likely to cause failure in a structure
To access more topics go to the Combined Science Notes page.
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