MEPX
Chapter 5 of 12All chapters
  1. 1What engineers do
  2. 2The design process
  3. 3Forces and loads
  4. 4Stress, strain and materials
  5. 5Structures
  6. 6Mechanisms
  7. 7Electrical basics
  8. 8Energy in machines
  9. 9Manufacturing and tolerances
  10. 10Safety factors and failure
  11. 11Testing and standards
  12. 12Responsibility

Chapter 5 of 12

Structures

Beams, columns and triangles.

How load travels

Every load must reach the ground through a path. A beam bends, with the top in compression and the bottom in tension, which is why an I-beam puts material where the stress is.

  • A triangle cannot change shape without changing the length of a side, so it is stiff.
  • A rectangle can lean into a parallelogram, which is why bracing turns it into triangles.

Buckling

A long slender column can fail sideways long before the material is crushed. That is a stability failure rather than a strength one, and it depends on length and shape more than on the material.