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Application Sheets:: Difference between revisions

261 bytes added ,  18:10, 25 December 2020
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== Force Resolution: ==
== 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 sheet ===
=== 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 = σu/σw
Factor of Safety <math>=\frac{\sigma_u}{\sigma_w}</math>


* σu is the ultimate tensile stress
* <math>\sigma_u
* σw is the working stress
</math> is the ultimate tensile stress
* <math>\sigma_w
</math> is the working stress


==== Data input ====
==== Data input ====
Force in stay Ft = 529 kN = 529*10^3
Force in stay: <math>F_t=529kN=5.29\times10^5N
</math>


Diameter of the stay D = 25 mm
Diameter of the stay: <math>D=25mm
</math>


Cable stay ultimate tensile stress σu = 345 N/mm2
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 = πD2 /4 = π*25^2/4 = 491 mm2
Area of stay: <math>A=\frac{\pi{}D^2}{4}=\frac{\pi\times25^2}{4}=491mm^2
</math>


Stress in stay σw = Ft/A = 529*10^3/491 = 1077 N/mm2
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 = σu/σw = 345/1077 = 0.32  this is much less than the required FoS of 3.0 so the design is not acceptable
<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