Analysis Inputs - Members Tab

This window is displayed when you create a new analysis or open an existing analysis. It is displayed as a floating window separate from the main application window. Closing this window will not close the analysis itself and will not lose any information about the analysis. To redisplay this window (when an analysis is open), select Analysis Inputs from the View menu, or press F4.

This tab contains inputs for the members in the analysis. Each row in the grid represents a member in the analysis. See also General Tab, Supports Tab, Loadings Tab, Combinations Tab, and Notes Tab.

SectionThe name of the section file to use for the member. This drop-down list contains all of the sections currently open in CFS. To add a different section to an analysis, you must first open the section. To add a member, enter its section name in the blank row after the last member. Each member in an analysis may use a different section.
Start LocationThe global longitudinal position of the ‘left’ end of the member (‘top’ end for columns). Multiple members must be continuous. Members may overlap but you cannot have gaps between members. Lapped members are assumed to provide full continuity.
End LocationThe global longitudinal position of the ‘right’ end of the member (‘bottom’ end for columns). This location must be greater than the start location, otherwise they will get swapped.
Braced FlangeFor members having one flange fastened to deck, sheathing, roof system, or other continually connected system, select the flange that is attached: Bottom, Top, Left, or Right. Otherwise, select None. These flange definitions refer to the orientation of the cross section.
RIf there is a braced flange, enter the moment reduction factor as defined in the AISI or ASCE Specification for your situation. For example:
      R=0.70 for continuous span Z sections
      R=0.60 for continuous span C sections
      R=0.70 for simple span C or Z section, depth £ 6.5"
      R=0.65 for simple span C or Z section, 6.5" < depth £ 8.5"
      R=0.50 for simple span Z section, 8.5" < depth £ 12"
      R=0.40 for simple span C section, 8.5" < depth £ 12"
Stiffness, kf The rotational stiffness provided to the braced flange by connection to the bracing material (deck, sheathing, etc.). This stiffness is incorporated in the distortional buckling calculations for the flange which is braced (bottom, top, left, or right). The units for this input are moment/radian/unit length (such as k-in/rad/in) which is then reduced to a force (such as k). Refer to the AISI Specification and Commentary for more information on determining what value to use.
Length, LmThe distance along the length of the member between discrete rigid restraints that restrict distortional buckling. If there are no discrete restraints for distortional buckling, leave this as a large value (such as the span length) and CFS will calculate the distortional buckling wavelength. If the member is fully restricted against distortional buckling, use Lm = 0. If the shape does not have a distortional buckling failure mode, the value of Lm has no effect.

In cases where rotational stiffness is provided to the braced flange by connection to bracing material, Lm does not represent the spacing between fasteners. It is the distance between rigid restraints against distortional buckling, if they exist.
ex, eyThe load eccentricity in the X and Y direction, measured from the origin of the section. Positive ex is horizontal to the right of the origin and positive ey is vertically above the origin. The combination of the axial loads and these eccentricities produce additional bending moments. The combination of transverse loads and these eccentricities affect the magnitude of torsional loads applied to the member. For more information, see Torsion Analysis