 # 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

The material constants are:
• 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.

Note: Poisson's Ratio must always be defined 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 REFerence point are discussed in G.4.3 Relationship Between Global and Local Coordinates and are input as part of the member constants.

## Material Definitions

Alternately, you may define the constants of a material in a material definition. This can include the analytical and design properties for the material. These material definitions are then assigned to the members, elements, and solids.

Note: A BETA is a geometric property and must be assigned separately from the material definition.