# G.12 Material Properties

STAAD.Pro allows you to define the properties of materials by two different methods. By assigning individual constants to members, elements, or solids or by creating a material definition and then assigning this.

## Material Constants

- modulus of elasticity (
`E`), - weight density (
`DEN`), - Poisson's ratio (
`POISS`), - coefficient of thermal expansion (
`ALPHA`), - composite damping ratio,
- and beta angle (
`BETA`) or coordinates for any reference (`REF`) point.

The modulus of elasticity, E, value for members must be provided or the analysis will not be performed. Weight density (`DEN`) is used only when selfweight of the structure is to be taken into account. Poisson's ratio (`POISS`) is used to calculate the shear modulus (commonly known as G) by the formula,

G = 0.5⋅E/(1 + POISS)

If Poisson's ratio is not provided, STAAD.Pro will assume a value for this quantity based on the value of E.

*after*the Modulus of Elasticity for a given member/element.

The coefficient of thermal expansion (`ALPHA`) is used to calculate the expansion of the members if temperature loads are applied. The temperature unit for temperature load and `ALPHA` has to be the same.

The composite damping ratio is used to compute the damping ratio for each mode in a dynamic solution. This is only useful if there are several materials with different damping ratios.

`BETA` angle and `REF`erence point are discussed in G.4.3 Relationship Between Global and Local Coordinates and are input as part of the member constants.