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TR.20.2 Prismatic Property Specification

The following commands are used to specify section properties for prismatic cross-sections.

General Format

For the PRISMATIC specification, properties are provided directly (End each line but last with a hyphen "-") as follows:

property-spec  = * { AX f1 | IX f2 | IY f3 | IZ f4 | AY f5 | AZ f6 | YD f7 | ZD f8 | YB f9 | ZB f10 }

Prismatic property nomenclature for a Tee and Trapezoidal section


  • AX    f1    =   Cross sectional area of the member. Set to zero for TEE, Rectangular, Trapezoid, or circular.
  • IX     f2    =   Torsional constant.
  • IY      f3    =   Moment of inertia about local y-axis.
  • IZ      f4    =   Moment of inertia about local z-axis (usually major).
  • AY    f5    =   Effective shear area in local y-axis.
  • AZ    f6    =   Effective shear area in local z-axis.

If any of the previous six parameters are omitted, it will be calculated from the YD, ZD, YB, and/or ZB dimensions.

  • YD    f7    =   Depth of the member in local y direction. Used as the diameter of section for circular members.
  • ZD    f8    =   Depth of the member in local z direction. If ZD is not provided and YD is provided, the section will be assumed to be circular.
  • YB    f9    =   Depth of stem for T-section.
  • ZB    f10  =   Width of stem for T-section or bottom width for TRAPEZOIDAL section.

The values that STAAD calculates for the omitted terms can be obtained by specifying the command PRINT MEMBER PROPERTIES.

The values of many of the derived properties like shear areas (AY, AZ), section modulii (SY, SZ), etc. will be shown in the output file.

This command can be used regardless of the manner in which the properties are specified (e.g., PRISMATIC, user table, built-in table).