Class 1 and Class 2 I-Shaped Sections

Members required to resist both bending moments and an axial compressive force shall be proportioned so that:

where

Cu and Mu	=	= the maximum load effects in compression and bending, respectively, including stability effects as defined in Cl. 8.7.
β	=	= 0.6 + 0.4λy ≤ 0.85
λy	=	= the nondimensional slenderness parameter about the y-y axis

The capacity of the member shall be examined for:

1. cross-sectional strength (members in braced frames only), with β = 0.6, in which case:

   • C_r is as define din Cl. 13.3 with the value of λ = 0.
   • M_r is as defined in Cl. 13.5 (for the appropriate class of section), and
   • U_1x and U_1y are as defined in 13.8.4 but not less than 1.0, and

2. overall member strength, in which case:

   • C_r is as define din Cl. 13.3 with the value of K = 1, except that for strong-axis bending,
   • C_r = C_rx (see aslo 10.3.2),
   • M_r is as defined in Cl. 13.5 (for the appropriate class of section), and
   • U_1x and U_1y are as defined in 13.8.4 for members in braced frames, and
   • U_1x and U_1y are taken as 1.0 for members in unbraced frames, and

3. lateral torsional bucking strength, when applicable, in which case:

   • C_r is as define din Cl. 13.3, and is based on weak-axis or torsional-flexural buckling (see also 10.3.3),
   • M_rx is as defined in 13.6 (for the appropriate class of section),
   • M_ry is as defined in 13.5 (for the appropriate class of section),
   • U_1x and U_1y are as defined in 13.8.4 for members in braced frames, and
   • U_1x is as defined in 13.8.4 but not less than 1.0, for members in braced frames, and
   • U_1y is as defined in 13.8.4 for members in braced frames

There parameters SSY and SSZ are used to indicate the sidesway in the local Y and Z axes, respectively.

In addition, the member shall meet the following criteria:

where

Mrx and Mry

=

= as described in 13.5 or 13.6, as appropriate

All Other Sections

Members required to resist both bending moments and an axial compressive force shall be proportioned so that:

where all terms are as defined in 13.8.2

The capacity of the member shall be examined for the following cases in a parallel manner to that in 13.8.2:

1. cross-sectional strength (members in braced frames and tapered members only),
2. overall member strength, and
3. lateral-torsional buckling strength.

Section Values of U₁

In lieu of a more detailed analysis, the value of U1 for the axis under consideration, accounting for the second-order effects due to the deformation of a member between its ends, shall be taken as:

where

ω1	=	= for the axis under consideration as defined in 13.8.4
Ce	=	$=\frac{{\pi }^{2}EI}{L^2}$ for the axis under consideration