Question

In a structure, why are the cable and wires are generally used?

• A. To resist shear stress
• B. As flexural member
• C. None of these
• D. As compression member

Answer 1

The correct option is C None of these

• Cables are structural elements that resist loads by developing axial tension.
• In the force analysis of cable, we commonly make two major assumptions:

(I) The cable is perfectly flexible
(II) The cable is inextensible

• By making the first assumption of perfectly flexible, the cable cannot resist any axial compression, bending moment or shear force. This assumption is perfectly valid when the cable takes the form of a spring or a very thin wire. In practice, however, the cable can also take the form of a thick metal stand or a wire rope due to larger diameter and higher elastic modulus.
• By virtue of second assumption, the cable is assumed to have a constant length, both before and after the application of load. This ensure us to treat the cable or a segment of it as rigid body for the purpose of force analysis.

Note:

• By virtue of cable flexibility, the geometric configuration of the cable changes with applied load. Hence the cable profile is made of straight line segment when it is subjected to concentrated load and will have a smooth curve when it is subjected to distributed load.
• System in which only axial forces operates are called funicular system e.g. cable, arches.