6.2column bracing

It is permitted to laterally brace an individual column at end and intermediate points along its length using either panel or point bracing.

User Note: This section provides requirements only for lateral bracing. Column lateral bracing is assumed to be located at the shear center of the column. When lateral bracing does not limit twist, the column is susceptible to torsional buckling as addressed in Section E4. When the lateral bracing is offset from the shear center, the column is susceptible to constrained-axis torsional buckling, which is also addressed in Section E4 and its accompanying Commentary.

6.2.1 Panel Bracing

The panel bracing system shall have the strength and stiffness specified in this section. The connection of the bracing system to the column shall have the strength specified in Section 6.2.2 for a point brace at that location.

User Note: If the stiffness of the connection to the panel bracing system is comparable to the stiffness of the panel bracing system itself, the panel bracing system and its connection to the column function as a panel and point bracing system arranged in series. Such cases may be evaluated using the alternative analysis methods listed in Section 6.1.

In the direction perpendicular to the longitudinal axis of the column, the required shear strength of the bracing system is

$V_{b r}=0.0005 P_{r}$

(A-6-1)

and the required shear stiffness of the bracing system is

(A-6-2a)

(A-6-2b)

$\phi=0.75$ (LRFD) $\quad \Omega=2.00$ (ASD)

where

$L_{b r}=$ unbraced length within the panel under consideration, in. (mm)

$P_{r}=$ required axial strength of the column within the panel under consideration using LRFD or ASD load combinations, kips (N)

6.2.2 Point Bracing

In the direction perpendicular to the longitudinal axis of the column, the required strength of end and intermediate point braces is

(A-6-3)

and the required stiffness of the brace is

(A-6-4a)

(A-6-4b)

$\phi=0.75$ (LRFD) $\quad \Omega=2.00$ (ASD)

where

$L_{b r}=$ unbraced length adjacent to the point brace, in. (mm)

• $\begin{aligned} P_{r} & =\text { largest of the required axial strengths of the column within the unbraced } \\ & \text { lengths adjacent to the point brace using LRFD or ASD load combinations, } \\ & \text { kips (N) }\end{aligned}$

When the unbraced lengths adjacent to a point brace have different $P_{r} / L_{b r}$ values, the larger value shall be used to determine the required brace stiffness.

For intermediate point bracing of an individual column, $L_{b r}$ in Equations A-6-4a or A-6-4b need not be taken as less than the maximum effective length, $L_{c}$, permitted for the column based upon the required axial strength, $P_{r}$.