Material constants are attributes like Modulus of Elasticity and Density which are required for operations like generating the stiffness matrix, computing selfweight, and for steel and concrete design.

In STAAD, there are two ways in which this data may be specified :

1. A two-step process that involves:

   1. Creating the material data by defining MATERIAL tags specified under the heading DEFINE MATERIAL (See TR.26.1 Define Material)
   2. Assigning them to individual members, plates and solids under the heading CONSTANTS (See TR.26.2 Specifying Constants for Members and Elements)

   This will create commands as shown below:

   Part 1DEFINE MATERIAL
   ... name
   ...
   ...
   END MATERIAL
    						
   Part 2CONSTANTS
   MATERIAL name ...

2. Assign material attributes explicitly by specifying the individual constants (See TR.26.2 Specifying Constants for Members and Elements).

   CONSTANTS
   E ...
   POISSON .

See TR.26.3 Surface Constants Specification for an explanation for the commands required to assign material data to Surface elements.