Hinged cantilever beam |
 |
|
In
the hinged cantilever design, only one end of the beam, the |
root, is attached to a support by some sort of hinge joint. An |
external load applied to the free end of the beam causes it to |
rotate around the point where it is hinged. In diagrams of
this |
beam a triangle symbol is usually placed at the end of the beam |
that is hinged to denote that it can rotate about the support but |
it
cannot move vertically or horizontally (Fig. 137
). |
click image to enlarge |
|
. |
 |
 |
click image to enlarge |
|
Fig. 136 - Hinged cantilever beam
(scale model) |
Fig. 137 - Diagram - hinged cantilever beam |
|
. |
Examples
of hinged cantilever beams include hinged doors, draw bridges, ailerons,
flaps, |
bird
wings, arms, etc. |
. |
Fixed cantilever beam |
 |
|
If
one end of a beam is fixed to its support |
so
that it cannot rotate it is called a fixed |
cantilever beam. Examples include diving |
boards, airplane wings, posts, poles, masts, |
|
trees,
branches, etc. When an external load is applied perpendicular to the
free end of the |
beam it
will exert a force that will try to make the beam rotate in the direction
of the force. |
But
because the root of the beam is fixed to a support it cannot rotate freely
and the beam |
will
tend to bend instead. The force will be distributed along the length
of the beam as |
tensile
and compressive stresses and will be concentrated at the root.. The
amount of force |
exerted
on the root depends on the size of the load and the distance from the root
that it is |
applied.
This is called the bending moment and can be expressed mathematically as: |
|
M = P L
where M = bending moment |
P = load (expressed in Newtons or lbs.) |
L = distance from the root (expressed in meters or feet) |
. |
Back to
Knowhere |
 |
Page 90 -
Building Stability - Cantilever beams |
 |
|