H8Coupled composite plate shear walls—concrete filled (CC-PSW/cf)

H8.3a Stiffness

The effective flexural, axial, and shear stiffness of composite walls and filled composite coupling beams shall be calculated in accordance with Specification Section I1.5.

H8.3b Required Strength for Coupling Beams

The required strength for the coupling beams shall be determined based on analyses in conformance with the applicable building code.

H8.3c Required Strength for Composite Walls

The required strength for the composite walls shall be determined using the capacity-limited seismic load. The capacity-limited seismic load refers to the capacity-limited horizontal seismic load effect, $E_{c l}$, which shall be determined from an analysis in which all the coupling beams are assumed to develop plastic hinges at both ends with expected flexural capacity of $1.2 M_{p, \exp }$, and the maximum overturning moment is amplified to account for the increase in lateral loading from the formation of the earliest plastic hinges to the formation of plastic hinges in all coupling beams, where $M_{p, \exp }$ is defined in Section H8.5c. The earthquake-induced axial force in the walls for determining the required wall strength shall be calculated as the sum of the capacitylimited coupling beam shear forces, using Equation H8-7, along the height of the structure. The portion of the maximum overturning moment resisted by coupling action shall be calculated as the couple caused by the wall axial forces associated with the coupling beam strengths. The remaining portion of the earthquake-induced overturning moment shall be distributed to the composite walls in accordance with their flexural stiffness, while accounting for the effects of simultaneous axial force. The required axial and flexural strengths for the composite walls shall be determined directly from this analysis, while the required wall shear strengths determined from this analysis shall be amplified by a factor of 4.

H8.4a Area of Steel Requirements

The steel plates shall comprise at least 1%, but no more than 10%, of the total composite cross-sectional area.

H8.4b Steel Plate Slenderness Requirements

In regions of flexural yielding (at the base), the steel plate slenderness ratio, $b / t$, shall be limited as follows:

(H8-1)

where

• $E=\operatorname{modulus}$ of elasticity of steel
• = 29,000 ksi (200 000 MPa)
• $b=$ largest unsupported length of the plate between horizontal and vertical rows of steel anchors or tie bars, in. (mm)
• $t=$ thickness of plate, in. (mm)

H8.4c Tie Bar Spacing Requirements

The tie bar spacing-to-plate thickness ratio, $s_{t} / t$, shall be limited as follows:

(H8-2)

(H8-2M)

(H8-3)

where

$d_{\text {tie }}=$ diameter of tie bar, in. (mm)

$s_{t}=$ largest center-to-center spacing of the tie bars, in. (mm)

$t_{s c}=$ total thickness of composite plate shear wall, in. (mm)

H8.4d Tie Bar-to-Plate Connection

The tie bar-to-steel plate connection shall develop the full yield strength of the tie bar.

H8.5a Minimum Area of Steel

The cross-sectional area of the steel section shall comprise at least 1% of the total composite cross section of the coupling beam.

H8.5b Slenderness Requirements for Coupling Beams

The slenderness ratios of the flanges and webs of the filled composite coupling beam, $b_{c} / t_{f}$ and $h_{c} / t_{w}$, shall be limited as follows:

(H8-4)

where

$b_{c}=$ clear width of the coupling beam flange plate, in. (mm)

• $h_{c}=$ clear depth of the coupling beam web plate, in. (mm)
• $t_{f}=$ thickness of the coupling beam flange plate, in. (mm)

$t_{w}=$ thickness of the coupling beam web plate, in. (mm)

H8.5c Flexure-Critical Coupling Beams

The filled composite coupling beams shall be proportioned to be flexure-critical with expected shear strength, $V_{n, \exp}$, as follows:

(H8-6)

where

$L_{c b} \quad=$ clear span length of the coupling beam, in. (mm)

$M_{p, \exp }$ = expected flexural capacity of filled composite coupling beam calculated in accordance with Section H8.7a while using the expected yield strength, $R_{y} F_{y}$, for steel and the expected compressive strength, $R_{c} f_{c}^{\prime}$, for concrete, kip-in. (N-mm)

$V_{n, \exp }=$ expected shear strength of filled composite coupling beam calculated in accordance with Specification Section I4.2 while using the expected yield strength, $R_{y} F_{y}$, for steel and the expected compressive strength, $R_{c} f_{c}^{\prime}$, for concrete, kips (N)

H8.6a Tensile Strength

The nominal tensile strength shall be determined in accordance with Specification Section I2.3.

H8.6b Compressive Strength

The nominal compressive strength shall be determined in accordance with Specification Section I2.3.

H8.6c Flexural Strength

The nominal flexural strength shall be determined in accordance with Specification Section I3.5.

H8.6d Combined Axial Force and Flexure

The nominal strength of composite walls subjected to combined axial force and flexure shall be determined in accordance with Specification Section I5(c).

H8.6e Shear Strength

The nominal in-plane shear strength, $V_{n}$, shall be determined in accordance with Specification Section I4.4.

H8.7a Flexural Strength

The nominal flexural strength of composite coupling beams shall be determined in accordance with the Specification Section I1.2a.

H8.7b Shear Strength

The nominal shear strength, $V_{n}$, of the filled composite coupling beams shall be determined in accordance with Specification Section I4.2.

H8.8a Required Flexural Strength

The required flexural strength, $M_{u}$, for the coupling beam-to-wall connection shall be $120 \%$ of the expected flexural capacity of the coupling beam, $M_{p, \exp }$.

H8.8b Required Shear Strength

The required shear strength, $V_{u}$, for the coupling beam-to-wall connection shall be determined using the capacity-limited seismic load effect as follows:

(H8-7)

where

$\begin{aligned} L_{c b} & =\text { clear span length of the coupling beam, in. (mm) } \\ M_{p, \exp } & =\text { expected flexural capacity of filled composite coupling beam calculated } \\ & \text { using expected yield strength, } R_{y} F_{y} \text {, for steel and the expected } \\ & \text { compressive strength, } R_{c} f_{c}^{\prime} \text {, for concrete, kip-in. (N-mm) }\end{aligned}$

H8.8c Rotation Capacity

The coupling beam-to-wall connection shall be detailed to develop a rotation capacity of 0.030 rad before flexural strength decreases to 80% of the plastic flexural strength of the beam. Connection details that have been previously demonstrated to have adequate rotation capacity shall be approved for use. The available rotation capacity of the coupling beam using other connection details shall be verified through testing, advanced analysis calibrated to physical testing, or a combination thereof.

H8.9a Required Strength

The required strength for the composite wall-to-foundation connections shall be determined using the capacity-limited seismic load effect. The coupling beams shall be assumed to have developed plastic hinges at both ends with the expected flexural capacity of $1.2 M_{p, \exp }$. The composite walls shall also be assumed to have developed plastic hinges at the base with expected flexural capacity of $1.2 M_{p, \exp }$, while accounting for the effects of simultaneous axial force. The required shear strength for the composite wall-to-foundation connections shall be equal to the required shear strength for the composite walls calculated in accordance with Section H8.3c.