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Cable Structures
Cable Structures
Theory and Design of Structures I
Theory and Design of Structures I
Introduction
Introduction
Ropes
Chains
Wires
Cables
• Features
– Considerable strength in simple tension
– No resistance either to bending nor compression
• In the analysis, the bending moment is always
taken to be zero throughout its length
• For a vertically loaded cable (i.e. no external
horizontal force), the horizontal component H of
the tension is constant throughout
Introduction
Introduction
• Assumptions:
– The cable is perfectly flexible
– The cable is inextensible
– The cable is weightless
• Hence, an ideal cable:
– acts purely as a tension member
– would be perfectly straight between each
suspended load
Introduction
Introduction
Cable subjected to
Cable subjected to
Concentrated Loads
Concentrated Loads
• Find out the cable forces if l
1
= 20m, l
2
= 25m,
h
1
= 7.5m, h
2
= 12.5m, P = 400N
Example 1
Example 1
B
h
2
= 12.5m
l
2
= 25m
l
1
= 20m
S
2
S
1
C
A
h
1
= 7.5m
P = 400N
A weightless cable under a concentrated load
H
H
V
B
V
A
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View Full Document • Graphically,
by force
triangle,
• Alternatively, take moment of whole cable ACB about B
• Take moment of the portion AC about C
N
490
1
=
S
N
510
2
=
S
0
5
.
7
20
=
×
−
×
H
V
A
0
25
400
5
45
=
×
−
×
+
×
H
V
A
(1)
H
V
A
375
.
0
=
(2)
B
h
2
= 12.5m
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This note was uploaded on 12/01/2010 for the course CIVL 2007 taught by Professor Profchai during the Spring '10 term at HKU.
 Spring '10
 profchai

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