Three men who died in a crash while fighting a fire in the Sierra in
summer 2002 knew the half century

old aircraft they were flying wasn't
entirely safe.
They had friends who died in previous airtanker crashes while flying
under contract for the Forest ServiceThe Forest Service has stopped
using C

130As for fighting fires. The NTSB has said fatigue cracks were
found in the wings. The Forest Service report said the plane had 21,947
hours of flying time, mostly for the Air Force, and that a wing crack was
repaired in 1998. The report said earlier manufacturer tests on similar
planes found structural problems after 19,000 hours of service.
Beams are deformed by lateral loads. The first step in determining these
deformations is calculating the internal loading within the beam.
You should be able to:
I)
Calculate the reactions for standard loading of beams
II)
Draw shear and moment diagrams as a function of position along a beam
We will cover three main types of
beam:
(a) simple beam,
(b) cantilever beam,
and (c) beam with an overhang
Real constructions can be modeled as
ideal supports. Examples include
Beam supported on a wall: (a) actual
construction, and (b) representation as a
roller support.
Beam

to

column
connection:
(c) actual construction, and
(d) representation as a pin
support.
Pole anchored to a
concrete pier:
(e) actual construction, and
(f) representation as a fixed
support.
If we take a cross

section of a
cantilevered beam shown in (a) the
direction of V and M depend upon
which end of the section we use. We
therefore need to define a sign
convention
The sign convention is arbitrary but we will use the sign
convention above. If we take the left hand section then +ve V is
down and a +ve moment is counter

clockwise.
Example 1
Shear

force and bending

moment diagrams for a simple beam with
a concentrated load
Example 2
Shear

force and
bending

moment diagrams for a
simple beam with a uniform load
Example 3
Shear

force and bending

moment diagrams for a simple beam
with several concentrated loads
Example 4
. Simple beam with a uniform
load over part of the span
Example 5
. Cantilever beam with two
concentrated loads
Example 6.
Cantilever beam
with a uniform load
Example 7.
Beam with an
overhang
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