Loading a beam

Loading a beam

ZIMSEC O Level Combined Science Notes: Loading a beam

  • When a beam is loaded it will bend
  • Bending movement creates stress
  • The top of the beam is compressed and the underside is stretched
  • This is because there are compressive forces at the top and stretching/tensile forces at the underside
  • If the tensile force is greater than the tensile strength of the material it cracks on its underside
  • tensile strength-the resistance of a material to breaking under tension
  • If a beam is only supported on the centre tension forces occur at the top of the beam and compression on the underside

Neutral axis

  • The central axis of the beam is called theĀ neutral axis
  • Neutral axis-is that part of the beam that remains unstressed when the beam is bent/carrying a load
  • The section above the neutral axis shortens (due to compression)
  • The section below the neutral axis lengthens (due to tension)
  • The length of the neutral axis does not change.
  • Please note that on a centrally supported beam the section above the neutral axis lengthens and the one below shortens
  • On a loaded beam the tension are equal to the compression forces bu they act in the opposite direction
  • The greater the distance is from neutral axis the greater the tensile and compression forces

To access more topics go to the Combined Science Notes page.