The following prismatic properties are required for analysis:
 AX = Cross sectional area
 IX = Torsional constant
 IY = Moment of inertia about yaxis.
 IZ = Moment of inertia about zaxis.
In addition, the user may choose to specify the following properties:
 AY = Effective shear area for shear force parallel to local yaxis.
 AZ = Effective shear area for shear force parallel to local zaxis.
 YD = Depth of section parallel to local yaxis.
 ZD = Depth of section parallel to local zaxis.
For Tbeams, YD, ZD, YB & ZB must be specified. These terms, which are shown
in the next figure are:
 YD = Total depth of section (top fiber of flange to bottom fiber of web)
 ZD = Width of flange
 YB = Depth of stem
 ZB = Width of stem

Prismatic property nomenclature for a T and Trapezoidal section 
For Trapezoidal beams, YD, ZD & ZB must be specified. These terms, which too
are shown in the next figure are:
 YD = Total depth of section
 ZD = Width of section at top fiber
 ZB = Width of section at bottom fiber
Top & bottom are defined as positive side of the local Z axis, and negative side of
the local Z axis respectively.
STAAD automatically considers the additional deflection of members due to pure
shear (in addition to deflection due to ordinary bending theory). To ignore the
shear deflection, enter a SET SHEAR command before the joint coordinates. This
will bring results close to textbook results.
The depths in the two major directions (YD and ZD) are used in the program to
calculate the section moduli. These are needed only to calculate member stresses
or to perform concrete design. You can omit the YD & ZD values if stresses or
design of these members are of no interest.
To define a concrete member,you must not provide AX, but instead, provide YD
and ZD for a rectangular section and just YD for a circular section. If no moment
of inertia or shear areas are provided, the program will automatically calculate
these from YD and ZD.

Required Section Properties 
Table is offered to assist the user in specifying the necessary section values. It
lists, by structural type, the required section properties for any analysis. For the
PLANE or FLOOR type analyses, the choice of the required moment of inertia
depends upon the beta angle. If BETA equals zero, the required property is IZ.