Much of the design information and many of the design variables are described relative to the major and minor axes of the section used for each member. This corresponds to the same terminology used to describe the properties of a section e.g. Ixx for moment of inertia about the major (or strong) axis and Iyy about the minor (or weak) axis.

The coordinate systems corresponding to the naming conventions for the various results of analysis, section properties and design values are shown in the diagram above. Structure coordinates and global loads are defined relative to the Global Axes, member actions, deflections and stresses resulting from the Multiframe analysis are defined relative to the local member axes and design values are defined relative to the section axes. Whenever a design variable carries a subscript this indicates that it applies to the corresponding section axis. (E.g. fbx refers to the design bending stress about the x-axis)