H6Composite plate shear walls—concrete encased (C-PSW/ce)

H6.3a Webs

The analysis shall account for openings in the web.

H6.3b Other Members and Connections

Columns, beams, and connections in C-PSW/CE shall be designed to resist seismic forces determined from an analysis that includes the expected strength of the steel webs in shear, 0.6RyFyAsp, and any reinforced concrete portions of the wall active at the design earthquake displacement,

where

$A_{s p}=$ horizontal area of the stiffened steel plate, in. ${ }^{2}\left(\mathrm{~mm}^{2}\right)$

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

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

The VBE are permitted to yield at the base.

H6.4a Steel Plate Thickness

Steel plates with thickness less than 3/8 in. (10 mm) are not permitted.

H6.4b Stiffness of VBE

The VBE shall satisfy the requirements of Section F5.4a.

H6.4c HBE-to-VBE Connection Moment Ratio

The beam-column moment ratio shall satisfy the requirements of Section F5.4b.

H6.4d Bracing

HBE shall be braced to satisfy the requirements for moderately ductile members.

H6.4e Openings in Webs

Boundary members shall be provided around openings in shear wall webs as required by analysis.

H6.5a Basic Requirements

Steel and composite HBE and VBE shall satisfy the requirements of Section D1.1 for highly ductile members.

H6.5b Webs

The design shear strength, $\phi_{v} V_{n}$, for the limit state of shear yielding with a composite plate conforming to Section H6.5c, shall be determined as follows:

$V_{n}=0.6 A_{s p} F_{y}$ (H6-1)

$\begin{aligned} V_{n} & =0.6 A_{s p} F_{y} \\ \phi_{v} & =0.90 \text { (LRFD) }\end{aligned}$

where

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

The design shear strength of C-PSW/CE with a plate that does not meet the stiffening requirements in Section H6.5c shall be based upon the strength of the plate determined in accordance with Section F5.5 and shall satisfy the requirements of Specification Section G2.

H6.5c Concrete Stiffening Elements

The steel plate shall be stiffened by encasement or attachment to a reinforced concrete panel. Conformance to this requirement shall be demonstrated with an elastic plate buckling analysis showing that the composite wall is able to resist a nominal shear force equal to $V_{n}$, as determined in Section H6.5b.

The concrete thickness shall be a minimum of 4 in. (100 mm) on each side when concrete is provided on both sides of the steel plate and 8 in. (200 mm) when concrete is provided on one side of the steel plate. Steel headed stud anchors or other mechanical connectors shall be provided to prevent local buckling and separation of the plate and reinforced concrete. Longitudinal and transverse reinforcement shall be provided in the concrete encasement to meet or exceed the requirements in ACI 318, Sections 11.6 and 11.7. The reinforcement ratio in both directions shall not be less than 0.0025. The maximum spacing between bars shall not exceed 18 in. (450 mm).

H6.5d Boundary Members

Structural steel sections and composite boundary members shall be designed to resist the expected shear strength of steel plate and any reinforced concrete portions of the wall active at the design earthquake displacement. Composite and reinforced concrete boundary members shall also satisfy the requirements of Section H5.5b. Structural steel boundary members shall also satisfy the requirements of Section F5.

H6.5e Protected Zones

There are no designated protected zones.

H6.6a Demand Critical Welds

The following welds are demand critical welds and shall satisfy 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 met.

• (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.
• (c) Welds at HBE-to-VBE connections

H6.6b HBE-to-VBE Connections

HBE-to-VBE connections shall satisfy the requirements of Section F5.6b.

H6.6c Connections of Steel Plate to Boundary Elements

The steel plate shall be continuously welded or bolted on all edges to the structural steel framing and/or steel boundary members, or the steel component of the composite boundary members. Welds and/or slip-critical high-strength bolts required to develop the nominal shear strength of the plate shall be provided.

H6.6d Connections of Steel Plate to Reinforced Concrete Panel

The steel anchors between the steel plate and the reinforced concrete panel shall be designed to prevent its overall buckling. Steel anchors shall be designed to satisfy the following conditions.

H6.6d.1 Tension in the Connector

The steel anchor shall be designed to resist the tension force resulting from inelastic local buckling of the steel plate.

H6.6d.2 Shear in the Connector

The steel anchors collectively shall be designed to transfer the expected strength in shear of the steel plate or reinforced concrete panel, whichever is smaller.

H6.6e Column Splices

In addition to the requirements of Section D2.5, column splices shall comply with the requirements of this section. Where welds are used to make the splice, they shall be complete-joint-penetration groove welds. When column splices are not made with groove welds, they shall have a required flexural strength that is at least equal to the plastic moment, $M_{p c c}$, of the smaller composite column. The required shear strength of column web splices shall be at least equal to $\Sigma M_{p c c} / H$, where $\Sigma M_{p c c}$ is the sum of the plastic moments at the top and bottom ends of the composite column and $H$ is the height of the story. For composite columns, the plastic flexural strength shall satisfy the requirements of Specification Chapter I with consideration of the required axial strength, $P_{r c}$.