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CABLES

A cable is most often two or more wire running side by side and bonded, twisted or braided together to form a single assembly. Cables are used for lifting, hauling and towing or conveying force through tension. Cables are commonly used to support suspension bridges, as permanent guys for transmission towers, chimneys and building roofs.
Analysis of cables :
Cables are perfectly flexible members which are assumed to have no flexural strength. They carry loads by simple tension.
The reactions at supports (Ra,Ha,Rb,Hb) will be calculated by using three static equations and forth equation is obtained from consideration that the Bending moment at any point in the cable is zero.

Shape of the cable: 
Cable subjected to concentrated loads, will take the shape of funicular polygon. 
cables - parabolic shape 
If it is loaded with uniform distributed load along the horizontal span, it will take the shape of Parabola.
when a cable supports a load that is uniform per unit length of cable itself (ie,self weight) ,it takes the form of a Catenary.
A hanging chain forms a catenary. 
PROBLEM 1
A suspension cable is supported at A and B, 120m. horizontally apart with B higher than A by 48m. Concentrated loads of 100kN, 200kN and 100kN were applied at a distance of 30m, 60m and 90m respectively from A. The cable sags a distance of 30m. measured from the chord AB at the point where the 200 kN is applied. Compute the horizontal reaction at the supports.

SOLUTION :
Ra +Rb = 400
Ra = Rb = 200 ( DUE TO SIMMENTARY OF LOADING )
M1 = 200(30)
M1 = 6000
M2 = 6000 + 100(30)
M2 = 9000
M2 = H d
9000 = H(30)
H = 300kN
PROBLEM 2
A suspension cable is supported at A and B, 120m, horizontally apart with B higher than A by 15m. The cable sags a distance of 10m. from the chord joining A and B at the midspan,compute the horizontal reaction at the supports. 


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Comments

  1. Unknown9 March 2013 at 02:58

    I 'm anxious to see the complete solution to this problem. I guess the solution depends on the assumption that the cable is parabolic rather than hyperbolic.
    Regards.

    ReplyDelete
  2. Unknown13 April 2021 at 19:55

    Where is the solution

    ReplyDelete
  3. pappueleczo26 May 2023 at 03:23

    Great Article On Cable. thanks For Sharing Such a Great Article. Can you Please Expand this Article More With Additional Informations Such as 10 Sq mm cable Price

    ReplyDelete

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