ZIMSEC O Level Combined Science Notes: The relationship between a beam’s strength and depth
- A beam is stronger if it’s depth if it has greater depth
- For example if a plank is turned on its narrow side it is stronger than when it is lying in its wider side
Beams in nature and engineering
- Where the load is applied in any direction such as in
- Engineering structures
- Biological structures such as the human body
- In such cases a hollow cylindrical beam(tube) is ideal
- For example long bones, lamp posts, chair legs, building columns etc
- In tubes the un-stretched material has been removed this makes them efficient and lighter
- It would be difficult for animals such as humans to walk with solid beams
- Tubes are equally strong in all directions including at right angles to the surface.
- Square tubes are not as strong as tube beams in this regard.
- A beam must be light and strong
- Cylindrical beams achieve this by removing unstretched material
- This increases their mass to strength ratio
- A beam must also be thick in order to support extra weight
- It must not be too long as this will result in it weakening the structure
- beams in tall structure tend to be cylindrical
- This is because tubes tend to crease rather than crack when placed under compression
- When cylindrical tubes are placed under pressure they are likely to buckle
- Buckling occurs when the beam is not strong enough to resist shear forces
- This can be prevented by making the beams thicker or by increasing their cylindrical diameter
To access more topics go to the Combined Science Notes page.