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Chapter 6
Cables
Summary

6.1 Introduction
To use cable construction effectively, the designer must deal with two problems:
1. Preventing large displacements and oscillations fromdeveloping in cables that carry live loads whose magnitude or direction changes with time.
2. Providing an efficient means of anchoring the large tensile force carried by cables.
In a typical cableanalysis the designer establishes the position of the end supports, the magnitude of the applied loads, and the elevation of one other point on the cable axis ( often the sag at midspan). Based on theseparameters, the designer applies cable theory to compute the end reactions, the force in the cable at all other points, and the position of other points along the cable axis.

6.2 Characteristics ofcables
Cables, which are made of a group of high-strength wires twisted together to form a strand, have an ultimate tensile strength of approximately 270 kips/in2 (1862 Mpa).
Yield pointincreases, ductility reduces.
Elongation 7 to 8 percent
Modulus of elasticity of approximately 26.000 kips/in2

6.3 Variation of Cable Force
If the cable tension is expressed in terms of the horizontalcomponent H and the cable slope Ɵ.
T= HcosƟ

6.4 Analysis of a Cable Supporting Gravity (Vertical) Loads

When a set of concentrated loads is applied to a cable of negligible weight, the cabledeflects into a series of linear segments. The resulting shape is called the funicular polygon.
Four equilibrium equations are available to compute the four reaction components supplied by thesupports. These equations include the three equations of static equilibrium applied to the free body of the cable and a condition equation, ∑Mz = 0.
Typically, the designer sets the maximum sag to ensureboth a required clearance and a economical design.

6.5 General cable theorem:
At any point on the cable supportin vertical loads, the product of the cable sag h and the horizontal component H of...