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

Buckling

• 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.