The Elasticity and Shear Modulus are pole material properties that define how rigid the pole material is. Together with geometry of pole's cross section they define how a pole will deflect, bend, elongate, compress, and twist when a load is applied to it.
Deflection effects are visible only in results acquired by Finite Element Analysis (FEA), whereas static analysis uses infinitely rigid poles, and hence will not deflect.
Elasticity, also known as modulus of elasticity or Young's modulus, is a measure of how much the pole will deflect when a load is applied to it. That is, how the pole will compress or elongate in response to a force. The higher the value for the Elasticity the more rigid the pole will be.
Shear Modulus, in combination with the torsional constant, will determine how much the pole twists under torsion and shears under shear force. The higher the value of the Shear Modulus the less the pole will twist and shear.
Poisson’s Ratio is a material property which describes a material's behaviour when being stretched or compressed, defining how much a material narrows / bulges when it is stretched / compressed. To illustrate consider someone pulling on a rubber band, as the rubber band stretches and becomes longer it also becomes thinner. The amount the width of an object changes in response to a change in length is the Poisson’s Ratio. A typical value for the Poisson's Ratio is 0.3.
Elasticity and Shear Modulus are expressed in terms of each other by using Poisson's Ratio as shown below.
In the pole library changing the Elasticity will automatically update the Shear Modulus by keeping the Poisson's Ratio the same. Changing the Shear Modulus will not change the Elasticity but will update the Poisson's Ratio. Likewise changing the Poisson's Ratio will not change the Elasticity but will update the Shear Modulus.