This window is displayed when you select Member Check from the Compute menu, and the active window is a section. After you enter the appropriate values, press the OK button and the Member Check output will be displayed.
| Lx, Ly, Lt | The unbraced lengths of the member for buckling about the X axis (in the Y direction), buckling about the Y axis (in the X direction), and torsional buckling, respectively. For lateral-torsional buckling of beams symmetrical about the X axis and bending about the X axis, Ly and Lt are the controlling unbraced lengths. |
| Kx, Ky, Kt | The effective length factors applied to the respective unbraced lengths. A value of 0 indicates a fully braced condition, where internal forces resulting from loads in that direction are set to 0. |
| Lm | The 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 sheathing, Lm does not represent the spacing between fasteners. It is the distance between rigid restraints against distortional buckling, if they exist. |
| Cbx, Cby | The bending coefficients used to determine the elastic critical moments for the member about the X axis and Y axis, respectively. The value is dependent on the moment gradient throughout the unbraced length. You may conservatively use the default value of 1. For bending about a non-symmetric axis, you must enter the reciprocal of CTF as the value of Cb, which may also be conservatively set to 1. |
| Cmx, Cmy | The moment coefficients used in the combined compressive axial load and bending interaction equation, for moments about the X axis and Y axis, respectively. You may conservatively use the default value of 1. |
| Braced Flange | For 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. |
| Reduction Factor, R | If 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. |
| Mx and My include P-δ effects |
Choosing this option will prevent moment amplifiers from being applied due to axial compression load. |
| P | The axial force (factored for LRFD) applied to the section. Positive loads are compression and negative loads are tension. |
| ex, ey | The axial 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 load and these eccentricities produces additional bending moment if the unbraced length is greater than zero. |
| Mx | The moment (factored for LRFD) about the X axis applied to the section. Positive moments produce compression above the X axis. |
| Vy | The shear force (factored for LRFD) in the Y direction applied to the section. This generally accompanies a moment about the X axis. |
| My | The moment (factored for LRFD) about the Y axis applied to the section. Positive moments produce compression to the right of the Y axis. |
| Vx | The shear force (factored for LRFD) in the X direction applied to the section. This generally accompanies a moment about the Y axis. |
| B | The torsional bimoment (factored for LRFD) applied to the section. The sign of the bimoment is very important when combined with bending. For a C section with a vertical web, a positive bimoment causes tension in the upper-right and lower-left quadrants of the section, and causes compression in the upper-left and lower-right quadrants of the section. |