Three men who died in a crash while fighting a fire in the Sierra in

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26 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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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