1. Simple Cable Statics

2. A flexible cable will assume a specific geometry when acted on by one or more point loads. This geometry is dependent on the relative magnitude and locations of each load, the length of the cable, and the height of the supports.
The designer usually has little control over the loads but can select the length of the cable, thereby controlling the sag, and the support locations.

3. In general, the greater the sag, the less will be the force in the cable.
For reasons of Equilibrium, a taut cable of very slight sag will have to withstand tremendous internal forces.
Analysis of one-way cable systems is made simple by the fact that a cable has effectively zero moment resistance. It will take a straight-line geometry between the loads.
Each cable segment then acts like a two-force tension member. Each load point is held in concurrent equilibrium by the load and two internal cable forces, one on each side of the load.

4. If the loads are applied vertically, the horizontal component of the cable force is a constant throughout the cable, and only the vertical component varies from segment to segment.
Because the vertical component is dependent on the cable slope, the largest tension in the cable will occur where the cable slope is greatest, usually at the highest cable support.

5. Forces Analysis B ِ 100 KN 18 m 100 KN y A 9 m D C 18 m 18 m 18 m Ay AAx C
100 KN
60 KN A
120 KN 60 KN 40 KN
40 KN C
120 KN C + D
120 KN
120 KN
120 KN
120 KN
60 KN
40 KN C

6. Segment DB + B D D 140 KN=By 120 KN=Bx 100 KN 140 KN 120 KN 120 KN

7. The ratio of the components Ax and Ay can be obtained from the slope of the cable segment AC, that is:
(1) M+
Substituting from eq. (1) in eq. (2)
Substituting in eq. (3)
By =140 kN
The tension force in segment AC is obtained from the components Ax and Ay and as follows:

8. The tension force in segment CD is obtained from the vertical equilibrium of either point C or D as shown in the previous force analysis system. Alternatively, it can be obtained from its slop after calculating the vertical distances y and d, hence:
If we denote the vertical component of the tension force in segment CD as Fy, then
The tension force in segment CD is then:
The tension force in segment DB is obtained from Bx and By, that is:
The largest tension occurs in cable segment BD because the segment slope is greatest