Efforts

The structures are intended to withstand external loads without deforming or breaking. As a result of these external loads, the structures support internal forces called efforts.

Loads and efforts

Load
It is an external force acting on a structure. It can be a weight, a push, a thermal expansion, etc.
Effort
Internal stress or force that supports a structure as a result of external loads.

For example, a person sitting on a chair is a load on the chair. Due to this load, the legs of the chair support a compressive effort.

There are 5 different efforts. Each one is explained below.

Traction

Tensile stress tends to stretch the structure:

_images/esfuerzo-traccion.png

Examples of elements that support this effort are:

  • Cadenas de un columpio.
  • Cable de una grúa.

Compression

The compressive stress tends to compress the structure:

_images/esfuerzo-compresion.png

Examples of elements that support this effort are:

  • Patas de una silla.
  • Columnas de un edificio.

Flex

The bending stress tends to bend the structure:

_images/esfuerzo-flexion.png

Examples of elements that support this effort are:

  • Tablero de una silla.
  • Suelos de edificios.
  • Brazo de una grúa.

Torque

Torque tends to twist the structure:

_images/esfuerzo-torsion.png

Examples of elements that support this effort are:

  • Eje de un destornillador.
  • Llave al girar.
  • Eje de un grifo.

Cut or shear

The shear stress or shear stress tends to cut the structure in two:

_images/esfuerzo-cortante.png

Examples of elements that support this effort are:

  • Papel cortado con tijeras.
  • Viga horizontal que apoya sobre viga vertical.
  • Tornillo que soporta un cuadro.

Exercises

  1. Find two examples of tensile stresses that are not on this page.

  2. Find two examples of compression stresses that are not on this page.

  3. Find two examples of bending stresses that are not on this page.

  4. Find two examples of torque that are not on this page.

  5. Find two examples of shear or shear stresses that are not on this page.

  6. Draw and name the forces that appear in a swing when a child climbs on the seat.

    _images/mecan-columpio.png

  7. Analyze the stresses that appear in a table when a weight is placed on top of it.

  8. Analyze the stresses that appear in a crane when it lifts a load.