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== | == Crane Tension Cable: == | ||
'''Context''' Design of a tower crane | '''Context''' Design of a tower crane | ||
'''Objective''' To assess the adequacy of the cable stay for the jib | '''Objective''' To assess the adequacy of the cable stay for the jib | ||
=== Concepts used in this application | === Concepts used in this application shee === | ||
* Force: applied load, moments, force resolution | * Force: applied load, moments, force resolution | ||
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==== Criterion ==== | ==== Criterion ==== | ||
Factor of Safety = | Factor of Safety <math>=\frac{\sigma_u}{\sigma_w}</math> | ||
* | * <math>\sigma_u | ||
* | </math> is the ultimate tensile stress | ||
* <math>\sigma_w | |||
</math> is the working stress | |||
==== Data input ==== | ==== Data input ==== | ||
Force in stay | Force in stay: <math>F_t=529kN=5.29\times10^5N | ||
</math> | |||
Diameter of the stay D = | Diameter of the stay: <math>D=25mm | ||
</math> | |||
Cable stay ultimate tensile stress | Cable stay ultimate tensile stress: <math>\sigma_u=345N/mm^2 | ||
</math> | |||
Minimum required FoS = 3.0 | Minimum required: <math>FoS = 3.0 | ||
</math> | |||
==== Calculations ==== | ==== Calculations ==== | ||
Area of stay A = | Area of stay: <math>A=\frac{\pi{}D^2}{4}=\frac{\pi\times25^2}{4}=491mm^2 | ||
</math> | |||
Stress in stay | Stress in stay: <math>\sigma_w=\frac{F_t}{A}=\frac{5.29\times10^5}{491}=1077N/mm^2 | ||
</math> | |||
==== Apply the criterion ==== | ==== Apply the criterion ==== | ||
FoS = | <math>FoS = \frac{\sigma_u}{\sigma_w}=\frac{345}{1077}=0.32 | ||
</math> <math>\ll 3.0 | |||
</math> | |||
This is much less than the required FoS of 3.0 so the design is not acceptable | |||
Decision: cable size must be increased | Decision: cable size must be increased | ||