You can see the drawing.
- When part of a beam is bent one way and part the
other way, the place where the curvature changes from one to the other is
called a point of contraflexure. It is like the middle part of the letter
"S". At this point the bending moment falls to zero. A good idea of what this is like
can be seen by laying a thin lath across a support, so that both ends drop
downwards, and then lifting one end till it bends the other way, i.e. one
part is curved upwards. When a continuous beam passes over a support it is
concave downwards, whereas between supports it is concave upwards. Points of
contraflexure occur where the concavity changes from upwards to downwards.
Since there is no bending effect at points of contraflexure, pins could be
fitted there without loss of strength.
ANTERIOR | ARRIBA | SIGUIENTE