Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Modeling Solutions
	Subarea:	Materials
	Original Author:	Bentley Technical Support Group

My STAAD output file contains the warning message:

**WARNING** THE POISSON'S RATIO HAS NOT BEEN SPECIFIED FOR ONE OR MORE
MEMBERS/ELEMENTS/SOLIDS. THE DEFAULT VALUE HAS BEEN SET FOR THE SAME.

What does this message mean?

The Poisson's ratio is one of the fundamental material properties required to perform the analysis of a structure. It is generally used to obtain the value of G (Modulus of Rigidity) using the relationship

E=2G(1+Poisson)

where E is the Young's modulus

If you have failed to specify the Poisson's ratio, STAAD attempts to "guess" the value of that term based on the value defined for E. For example, if E is in the neighbourhood of 29000 ksi (steel), Poisson's will be chosen to be about 0.30. If E is in the neighbourhood of 3150 ksi (concrete), Poisson's will be chosen to be about 0.17.

If you would like to see what value has been chosen by the program, you may specify the command

PRINT MATERIAL PROPERTIES

after all the CONSTANTs have been provided. The Poisson's ratio will be reported in the output file along with some of the other CONSTANTs.

It is best to specify a value explicitly instead of having the program estimate a value on its own.