H5Composite special shear walls (C-SSW)

AISC 341-22, Seismic Provisions for Structural Steel Buildings

Last Updated 29 Oct 2026

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H5.1 Scope

Composite special shear walls (C-SSW) shall be designed in conformance with this section. This section is applicable to reinforced concrete shear walls with composite boundary elements and coupled reinforced concrete shear walls, with or without composite boundary elements, with structural steel or composite coupling beams that connect two or more adjacent walls.

H5.2 Basis of Design

C-SSW designed in accordance with these provisions are expected to provide significant inelastic deformation capacity through yielding in the reinforced concrete walls and the steel or composite elements. Reinforced concrete wall elements shall be designed to provide inelastic deformations at the design story drift consistent with ACI 318, including Chapter 18. Structural steel and composite coupling beams shall be designed to provide inelastic deformations at the design earthquake displacement through yielding in flexure or shear. Coupling beam connections and the design of the walls shall be designed to account for the expected strength, including strain hardening in the coupling beams. Structural steel and composite boundary elements shall be designed to provide inelastic deformations at the design earthquake displacement through yielding due to axial force.

C-SSW systems shall satisfy the requirements of Section H4 and the shear wall requirements of ACI 318, including Chapter 18, except as modified in this section.

User Note: Steel coupling beams can be proportioned to be shear-critical or flexural-critical. Coupling beams with lengths $g \leq 1.6 M_{p} / V_{p}$ can be assumed to be shear-critical, where $g, M_{p}$ , and $V_{p}$ are defined in Section H5.5c. Coupling beams with lengths $g \geq 2.6 M_{p} / V_{p}$ may be considered to be flexure-critical. Coupling beam lengths between these two values are considered to yield in flexure and shear simultaneously.

H5.3 Analysis

Analysis requirements of Section H4.3 shall be met with the following exceptions:

(a) For wall piers, cracked effective stiffness values for elastic analysis shall be assigned in accordance with ACI 318, Chapter 6.
(b) Effects of shear distortion of the steel coupling beam shall be taken into account.

H5.4 System Requirements

For walls that are not part of coupled wall systems—in other words, isolated walls—there are no specific system-level requirements.

In coupled walls, it is permitted to redistribute coupling beam forces vertically to adjacent floors. The shear in any individual coupling beam shall not be reduced by more than 20% of the elastically determined value. The sum of the coupling beam shear resistance over the height of the building shall be greater than or equal to the sum of the elastically determined values. In addition, the following requirements shall be satisfied:

(a) In coupled walls, coupling beams shall be designed to yield over the height of the structure followed by yielding at the base of the wall piers.
(b) In coupled walls, the axial design strength of the wall at the balanced condition, $P_{b}$ , shall equal or exceed the total required compressive axial strength in a wall pier, computed as the sum of the required strengths attributed to the walls from the gravity load components of the lateral load combination plus the sum of the expected beam shear strengths increased by a factor of 1.1 to reflect the effects of strain hardening of all the coupling beams framing into the walls.

H5.5 Members

H5.5a Ductile Elements

Welding on steel coupling beams is permitted for attachment of stiffeners, as required in Section F3.5b.4.

H5.5b Boundary Members

Unencased structural steel columns shall satisfy the requirements of Section D1.1 for highly ductile members and Section H4.5a(a).

In addition to the requirements of Sections H4.3(b) and H4.5a(b), the requirements in this section shall apply to walls with concrete-encased structural steel boundary members. Concrete-encased structural steel boundary members that qualify as composite columns in Specification Chapter I shall meet the highly ductile member requirements of Section D1.4b.2. Otherwise, such members shall be designed as composite compression members to satisfy the requirements of ACI 318, including the special seismic requirements for boundary members in ACI 318, Section 18.10.6. Transverse reinforcement for confinement of the composite boundary member shall extend a distance of $2 h$ into the wall, where $h$ is the overall depth of the boundary member in the plane of the wall.

Headed studs or welded reinforcement anchors shall be provided as specified in Section H4.5a(c).

Wall longitudinal reinforcement as specified in Section H4.5b.1(d) shall be confined by transverse reinforcement that meets the requirements for boundary members of ACI 318, Section 18.10.6. Unless vertical transfer reinforcement is provided in accordance with Section H5.5c(e), transverse reinforcement satisfying ACI 318, Sections 18.7.5.2(a) through (e), over the distance calculated in accordance with ACI 318, Section 18.10.6.4(a), shall be provided between a height of $L_{e}$ below the bottom flange and $L_{e}$ above the top flange of an embedded steel section with a vertical spacing not exceeding the lesser of 8 in. (200 mm) and 8 times the diameter of the smallest longitudinal reinforcement confined by this transverse reinforcement.

H5.5c Steel Coupling Beams

The design and detailing of steel coupling beams shall satisfy the following:

(a) The embedment length, $L_{e}$ , of the coupling beam shall be computed from Equation H5-1 or H5-1M.

V_{b e}=1.54 \sqrt{f_{c}^{\prime}}\left(\frac{b_{w}}{b_{f}}\right)^{0.66} \beta_{1} b_{f} L_{e}\left(\frac{0.58-0.22 \beta_{1}}{0.88+\frac{g}{2 L_{e}}}\right)

(H5-1)

V_{b e}=4.04 \sqrt{f_{c}^{\prime}}\left(\frac{b_{w}}{b_{f}}\right)^{0.66} \beta_{1} b_{f} L_{e}\left(\frac{0.58-0.22 \beta_{1}}{0.88+\frac{g}{2 L_{e}}}\right)

(H5-1M)

where

$L_{e}=$ embedment length of coupling beam, considered to begin inside the first layer of confining reinforcement, nearest to the edge of the wall, in the wall boundary member, in. (mm)
$V_{b e}=$ expected shear strength of a steel coupling beam computed from Equation H5-2, kips (N)

\frac{2\left(1.1 R_{y}\right) M_{p}}{g} \leq\left(1.1 R_{y}\right) V_{p}

(H5-2)

$M_{p}=F_{y} Z$ , kip-in. (N-mm)

$F_{y}=$ specified minimum yield stress, ksi (MPa)

$Z \quad$ = plastic section modulus about the axis of bending, in. ${ }^{3}(\mathrm{~mm}^{3})$

$R_{y}=$ ratio of expected yield stress to specified minimum yield stress, $F_{y}$

$V_{p}=0.6 F_{y} A_{t w}$ , kips (N)

$A_{h w}=\text { area of structural steel beam web, in }^{2}\left(\mathrm{~mm}^{2}\right)$

$f_{c}^{\prime}=$ specified compressive strength of concrete, ksi (MPa)

g = clear span of the coupling beam plus the wall concrete cover at each end of the beam, in, (mm)

(b) Structural steel coupling beams shall satisfy the requirements of Section F3.5b, except that for built-up cross sections, the flange-to-web welds are permitted to be made with two-sided fillet, partial-joint-penetration, or complete-joint-penetration groove welds that develop the expected strength of the beam. When required in Section F3.5b.4, the coupling beam rotation shall be assumed as a 0.08 rad link rotation unless a smaller value is justified by rational analysis of the inelastic deformations that are expected under the design earthquake displacement. Face bearing plates shall be provided on both sides of the coupling beams at the face of the reinforced concrete wall. These plates shall meet the detailing requirements of Section F3.5b.4.
(c) Steel coupling beams shall comply with the requirements of Section D1.1 for highly ductile members. Flanges of coupling beams with I-shaped sections with $g \leq 1.6 M_{p} / V_{p}$ are permitted to satisfy the requirements for moderately ductile members.
(d) The requirements of Section H4.5b.1(c) shall be satisfied, except that the minimum value of $L_{e}$ shall be determined based on the calculations for shear strength given by Equation H5-1 or H5-1M rather than Equation H4-4 or H4-4M.

(e) The requirements of Section H4.5b.1(d) shall be satisfied with $V_{be}$ used instead of the required shear strength. The area of vertical reinforcement used to satisfy Section H4.5b.1(d) may include two regions of vertical transfer reinforcement attached to both the top and bottom flanges of the embedded member. The first region shall be located to coincide with the location of longitudinal wall rein- forcement closest to the face of the wall. The second region shall be placed a distance no less than $d/2$ from the termination of the embedment length. All transfer reinforcement shall meet the development length requirements of ACI 318, Chapter 18, where they engage the coupling beam flanges. It is permitted to use straight, hooked, or mechanical anchorage to provide development. It is permitted to use mechanical couplers welded to the flanges to attach the vertical transfer bars. The area of vertical transfer reinforcement required is computed by Equation H5-3: $A_{tb}\ge0.03\,f_{c}^{\prime}L_{e}b_{w}/F_{ys}$ (H5-3)

A_{t b} \geq 0.03 f_{c}^{\prime} L e b_{f} / F_{y s t r}

(H5-3)

where

$A_{t b}=$ area of transfer reinforcement required in each of the first and second regions attached to each of the top and bottom flanges, in. ${ }^{2}\left(\mathrm{~mm}^{2}\right)$

$F_{y s t r}=$ specified minimum yield stress of transfer reinforcement, ksi (MPa)

$b_{f}$ = width of beam flange, in. (mm)

$f_{c}^{\prime} \quad$ = specified compressive strength of concrete, ksi (MPa)

The area of vertical transfer reinforcement shall not exceed that computed by Equation H5-4:

\Sigma A_{t b}<0.08 L_{e} b_{w}-A_{s r}

(H5-4)

where

$\Sigma A_{t b}=$ total area of transfer reinforcement provided in both the first and second regions attached to either the top or bottom flange, in. ${ }^{2}\left(\mathrm{~mm}^{2}\right)$

$\begin{aligned} A_{s r} & =\text { area of longitudinal wall reinforcement provided over the embedment } \\ & \text { length, } L_{e}, \text { in. }^{2}\left(\mathrm{~mm}^{2}\right)\end{aligned}$

$\begin{aligned} b_{w} & =\text { width of wall, in. (mm) }\end{aligned}$

H5.5d Composite Coupling Beams

Encased composite sections serving as coupling beams shall satisfy the requirements of Section H5.5c, except for the following: The requirements of Section F3.5b.4 need not be met, the use of face bearing plates specified in Section H5.5c(b) need not be provided, and $V_{c e}$ shall replace $\left(1.1 R_{y}\right) V_{p}$ and $1.1 M_{p b e}$ shall replace $\left(1.1 R_{y}\right) M_{p}$ in Equation H5-2. $M_{p b e}$ shall be computed using Section G2.6d. The limiting expected shear strength, $V_{c e}$ , is as follows:

$V_{ce}=1.1R_{y}V_{p}+0.08\sqrt{R_{c}f_{c}^{\prime}}b_{wc}d_{c}+\frac{1.33R_{yr}A_{sr}F_{ysr}d_{c}}{s}$ (H5-5)

$V_{ce}=1.1R_{y}V_{p}+0.21\sqrt{R_{c}f_{c}^{\prime}}b_{wc}d_{c}+\frac{1.33R_{yr}A_{sr}F_{ysr}d_{c}}{s}$ (H5-5M)

where

$A_{s r}=\text { area of transverse reinforcement within } s, \text { in. }^{2}\left(\mathrm{~mm}^{2}\right)$

$F_{y s r}=$ specified minimum yield stress of transverse reinforcement, ksi (MPa)

$R_{c}=$ factor to account for expected strength of concrete $=1.3$
$R_{y r}=$ ratio of the expected yield stress of the transverse reinforcement material to the specified minimum yield stress, $F_{y s r}$ , to be taken as the $R_{y}$ value from Table A3.2 for the corresponding steel reinforcement material

H5.5e Protected Zones

The clear span of the coupling beam between the faces of the shear walls shall be designated as a protected zone and shall satisfy the requirements of Section D1.3. Attachment of stiffeners, and face bearing plates as required by Section H5.5c(b), are permitted.

H5.6 Connections

H5.6a Demand Critical Welds

The following welds are demand critical welds and shall meet the requirements of Sections A3.4b and I2.3.

(a) Groove welds at column splices
(b) Welds at the column-to-base plate connections
Exception: Welds need not be considered demand critical when both of the fol- lowing conditions are satisfied.
(1) Column hinging at, or near, the base plate is precluded by conditions of restraint.
(2) There is no net tension under load combinations including the overstrength seismic load.

H5.6b Column Splices

Column splices shall be designed in accordance with the requirements of Section G2.6f.

H5Composite special shear walls (C-SSW)

AISC 341-22, Seismic Provisions for Structural Steel Buildings

Last Updated 29 Oct 2026

Hover any section to copy its link or text, ask Copilot about it, or bookmark it.

H5.1 Scope

H5.2 Basis of Design

C-SSW systems shall satisfy the requirements of Section H4 and the shear wall requirements of ACI 318, including Chapter 18, except as modified in this section.

H5.3 Analysis

Analysis requirements of Section H4.3 shall be met with the following exceptions:

(a) For wall piers, cracked effective stiffness values for elastic analysis shall be assigned in accordance with ACI 318, Chapter 6.
(b) Effects of shear distortion of the steel coupling beam shall be taken into account.

H5.4 System Requirements

For walls that are not part of coupled wall systems—in other words, isolated walls—there are no specific system-level requirements.

(a) In coupled walls, coupling beams shall be designed to yield over the height of the structure followed by yielding at the base of the wall piers.
(b) In coupled walls, the axial design strength of the wall at the balanced condition, $P_{b}$ , shall equal or exceed the total required compressive axial strength in a wall pier, computed as the sum of the required strengths attributed to the walls from the gravity load components of the lateral load combination plus the sum of the expected beam shear strengths increased by a factor of 1.1 to reflect the effects of strain hardening of all the coupling beams framing into the walls.

H5.5 Members

H5.5a Ductile Elements

Welding on steel coupling beams is permitted for attachment of stiffeners, as required in Section F3.5b.4.

H5.5b Boundary Members

Unencased structural steel columns shall satisfy the requirements of Section D1.1 for highly ductile members and Section H4.5a(a).

Headed studs or welded reinforcement anchors shall be provided as specified in Section H4.5a(c).

H5.5c Steel Coupling Beams

The design and detailing of steel coupling beams shall satisfy the following:

(a) The embedment length, $L_{e}$ , of the coupling beam shall be computed from Equation H5-1 or H5-1M.

V_{b e}=1.54 \sqrt{f_{c}^{\prime}}\left(\frac{b_{w}}{b_{f}}\right)^{0.66} \beta_{1} b_{f} L_{e}\left(\frac{0.58-0.22 \beta_{1}}{0.88+\frac{g}{2 L_{e}}}\right)

(H5-1)

V_{b e}=4.04 \sqrt{f_{c}^{\prime}}\left(\frac{b_{w}}{b_{f}}\right)^{0.66} \beta_{1} b_{f} L_{e}\left(\frac{0.58-0.22 \beta_{1}}{0.88+\frac{g}{2 L_{e}}}\right)

(H5-1M)

where

$L_{e}=$ embedment length of coupling beam, considered to begin inside the first layer of confining reinforcement, nearest to the edge of the wall, in the wall boundary member, in. (mm)
$V_{b e}=$ expected shear strength of a steel coupling beam computed from Equation H5-2, kips (N)

\frac{2\left(1.1 R_{y}\right) M_{p}}{g} \leq\left(1.1 R_{y}\right) V_{p}

(H5-2)

$M_{p}=F_{y} Z$ , kip-in. (N-mm)

$F_{y}=$ specified minimum yield stress, ksi (MPa)

$Z \quad$ = plastic section modulus about the axis of bending, in. ${ }^{3}(\mathrm{~mm}^{3})$

$R_{y}=$ ratio of expected yield stress to specified minimum yield stress, $F_{y}$

$V_{p}=0.6 F_{y} A_{t w}$ , kips (N)

$A_{h w}=\text { area of structural steel beam web, in }^{2}\left(\mathrm{~mm}^{2}\right)$

$f_{c}^{\prime}=$ specified compressive strength of concrete, ksi (MPa)

g = clear span of the coupling beam plus the wall concrete cover at each end of the beam, in, (mm)

(b) Structural steel coupling beams shall satisfy the requirements of Section F3.5b, except that for built-up cross sections, the flange-to-web welds are permitted to be made with two-sided fillet, partial-joint-penetration, or complete-joint-penetration groove welds that develop the expected strength of the beam. When required in Section F3.5b.4, the coupling beam rotation shall be assumed as a 0.08 rad link rotation unless a smaller value is justified by rational analysis of the inelastic deformations that are expected under the design earthquake displacement. Face bearing plates shall be provided on both sides of the coupling beams at the face of the reinforced concrete wall. These plates shall meet the detailing requirements of Section F3.5b.4.
(c) Steel coupling beams shall comply with the requirements of Section D1.1 for highly ductile members. Flanges of coupling beams with I-shaped sections with $g \leq 1.6 M_{p} / V_{p}$ are permitted to satisfy the requirements for moderately ductile members.
(d) The requirements of Section H4.5b.1(c) shall be satisfied, except that the minimum value of $L_{e}$ shall be determined based on the calculations for shear strength given by Equation H5-1 or H5-1M rather than Equation H4-4 or H4-4M.

A_{t b} \geq 0.03 f_{c}^{\prime} L e b_{f} / F_{y s t r}

(H5-3)

where

$A_{t b}=$ area of transfer reinforcement required in each of the first and second regions attached to each of the top and bottom flanges, in. ${ }^{2}\left(\mathrm{~mm}^{2}\right)$

$F_{y s t r}=$ specified minimum yield stress of transfer reinforcement, ksi (MPa)

$b_{f}$ = width of beam flange, in. (mm)

$f_{c}^{\prime} \quad$ = specified compressive strength of concrete, ksi (MPa)

The area of vertical transfer reinforcement shall not exceed that computed by Equation H5-4:

\Sigma A_{t b}<0.08 L_{e} b_{w}-A_{s r}

(H5-4)

where

$\Sigma A_{t b}=$ total area of transfer reinforcement provided in both the first and second regions attached to either the top or bottom flange, in. ${ }^{2}\left(\mathrm{~mm}^{2}\right)$

$\begin{aligned} A_{s r} & =\text { area of longitudinal wall reinforcement provided over the embedment } \\ & \text { length, } L_{e}, \text { in. }^{2}\left(\mathrm{~mm}^{2}\right)\end{aligned}$

$\begin{aligned} b_{w} & =\text { width of wall, in. (mm) }\end{aligned}$

H5.5d Composite Coupling Beams

$V_{ce}=1.1R_{y}V_{p}+0.08\sqrt{R_{c}f_{c}^{\prime}}b_{wc}d_{c}+\frac{1.33R_{yr}A_{sr}F_{ysr}d_{c}}{s}$ (H5-5)

$V_{ce}=1.1R_{y}V_{p}+0.21\sqrt{R_{c}f_{c}^{\prime}}b_{wc}d_{c}+\frac{1.33R_{yr}A_{sr}F_{ysr}d_{c}}{s}$ (H5-5M)

where

$A_{s r}=\text { area of transverse reinforcement within } s, \text { in. }^{2}\left(\mathrm{~mm}^{2}\right)$

$F_{y s r}=$ specified minimum yield stress of transverse reinforcement, ksi (MPa)

$R_{c}=$ factor to account for expected strength of concrete $=1.3$
$R_{y r}=$ ratio of the expected yield stress of the transverse reinforcement material to the specified minimum yield stress, $F_{y s r}$ , to be taken as the $R_{y}$ value from Table A3.2 for the corresponding steel reinforcement material

H5.5e Protected Zones

H5.6 Connections

H5.6a Demand Critical Welds

The following welds are demand critical welds and shall meet the requirements of Sections A3.4b and I2.3.

(a) Groove welds at column splices
(b) Welds at the column-to-base plate connections
Exception: Welds need not be considered demand critical when both of the fol- lowing conditions are satisfied.
(1) Column hinging at, or near, the base plate is precluded by conditions of restraint.
(2) There is no net tension under load combinations including the overstrength seismic load.

H5.6b Column Splices

Column splices shall be designed in accordance with the requirements of Section G2.6f.