A 70-ft long, ¾" diameter, 6 x 7 FC wire rope is resisting a tension force of 12-kips.  The elastic stretch of the steel wire rope given the following properties is most nearly: E = 10,000-ksi;  A = 0.288-in²

Solution:  The elongation or "stretch" of wire ropes must be considered in designing temporary bracing and lifting configurations.  Elongation comes from two sources: (1) constructional stretch is dependent on the classification and results primarily from a reduction in diameter as load is applied and the strands compact against each other. Constructional stretch is provided by the manufacturer and is always given.  (2) Elastic stretch is caused by deformation of the metal itself when load is applied.  Use the following equation to establish a value for elastic stretch:

Elastic Stretch = PL / AE

Where: P= change in load; L=length; A=area of wire rope; E=modulus of elasticity.

Elastic Stretch = 12-kips x 70-ft x 12-in/ft/ (0.288-in² *10,000-ksi)  = 3.5-in                              

                          = 3.5-in