1. Cable Structure
Cables are often used in engineering structures for support and to transmit loads from one member to another. When used to support suspension bridges, cables form the main load-carrying element in the structure.
Note: Cable can only carrying tensile force.

2. Parabolic equation of Cable

3. Cable supported at same level
Consider free body diagram at left hand side of C:

4. Maximum tensile force in the cable,

5. Cable supported at different level
Consider cable ACB’:

6. Consider cable A’CB:

7. But H1 = H2 = H, then
Lowest position equation
Vertical Reactions RA and RB
Tensile force in the cable at A and B

8. CABLE SUPPORT Two types – Sokong Takal Pandu, Roller Support
Driven pulley support
Smooth Pulley:
Tp = Tg =T
Reactions from tower
(menara):
Menara

9. Roller Support
Note:
To ensure the roller not moves laterally:
Equilibrium Vertically:

10. Example 7.1
Figure below shows a cable structure supported by frictionless roller which is located on top of tower. Determine:
Maximum and minimum tensile force exerted by the cable
Vertical reaction force exerted by tower at A and B

11. Solution
Find l1 and l2
Solving equations (a) and (b) give l1 = m and l2 = m
Find H or

12. Take H = kN
Find RA and RB in the cable
Find tensile force exerted by the cable (at A and B)
Maximum tensile force occurred at B, minimum tensile force occurred at C (lowest point in the cable) (=H= kN)

13. (b) Reaction forces exerted by the tower