# 17.5.2 *Concrete Breakout Strength of Anchor in Shear*

**of a single anchor or**

*V*_{cb}**of a group of anchors, shall not exceed:**

*V*_{cbg}(a) For shear force perpendicular to the edge on a single anchor

(17.5.2.1a) |

(b) For shear force perpendicular to the edge on a group of anchors

(17.5.2.1b) |

(c) For shear force parallel to an edge, ** V_{cb}** or

**shall be permitted to be twice the value of the shear force determined from Eq. (17.5.2.1a) or (17.5.2.1b), respectively, with the shear force assumed to act perpendicular to the edge and with**

*V*_{cbg}**ψ**taken equal to 1.0.

_{ed,V}(d) For anchors located at a corner, the limiting nominal concrete breakout strength shall be determined for each edge, and the minimum value shall be used.

Factors **ψ _{ec,V}**,

**ψ**,

_{ed,V}**ψ**, and

_{c,V}**ψ**are defined in 17.5.2.5, 17.5.2.6, 17.5.2.7, and 17.5.2.8, respectively.

_{h,V}**is the basic concrete breakout strength value for a single anchor.**

*V*_{b}**is the projected area of the failure surface on the side of the concrete member at its edge for a single anchor or a group of anchors. It shall be permitted to evaluate**

*A*_{Vc}**as the base of a truncated half-pyramid projected on the side face of the member where the top of the half-pyramid is given by the axis of the anchor row selected as critical. The value of**

*A*_{Vc}**shall be taken as the distance from the edge to this axis.**

*c*_{a}_{1}**shall not exceed**

*A*_{Vc}**, where**

*nA*_{Vco}**is the number of anchors in the group.**

*n*** A_{Vco}** is the projected area for a single anchor in a deep member with a distance from edges equal or greater than

**1.5**in the direction perpendicular to the shear force. It shall be permitted to evaluate

*c*_{a}_{1}**as the base of a half-pyramid with a side length parallel to the edge of**

*A*_{Vco}**3**and a depth of

*c*_{a}_{1}**1.5**

*c*_{a}_{1}A = 4.5(_{Vco}c_{a}_{1})^{2} | (17.5.2.1c) |

Where anchors are located at varying distances from the edge and the anchors are welded to the attachment so as to distribute the force to all anchors, it shall be permitted to evaluate the strength based on the distance to the farthest row of anchors from the edge. In this case, it shall be permitted to base the value of ** c_{a}_{1}** on the distance from the edge to the axis of the farthest anchor row that is selected as critical, and all of the shear shall be assumed to be carried by this critical anchor row alone.

**, shall be the smaller of (a) and (b):**

*V*_{b}(a) | (17.5.2.2a) |

where ** ℓ_{e}** is the load-bearing length of the anchor for shear:

** ℓ_{e} = h_{ef}** for anchors with a constant stiffness over the full length of embedded section, such as headed studs and post-installed anchors with one tubular shell over full length of the embedment depth;

** ℓ_{e} = 2d_{a}** for torque-controlled expansion anchors with a distance sleeve separated from expansion sleeve, and

**in all cases.**

*ℓ*≤ 8_{e}*d*_{a}(b) | (17.5.2.2b) |

^{3}/

_{8}in. and half of the anchor diameter, the basic concrete breakout strength in shear of a single anchor in cracked concrete,

**, shall be the smaller of Eq. (17.5.2.2b) and Eq. (17.5.2.3)**

*V*_{b}(17.5.2.3) |

where ** ℓ_{e}** is defined in 17.5.2.2 provided that:

(a) For groups of anchors, the strength is determined based on the strength of the row of anchors farthest from the edge

(b) Anchor spacing ** s** is not less than 2.5 in.

(c) Reinforcement is provided at the corners if *c _{a}*

_{2}≤ 1.5

*h*

_{ef}**and thickness**

*c*_{a}_{2}**are less than**

*h*_{a}**1.5**, the value of

*c*_{a}_{1}**used for the calculation of**

*c*_{a}_{1}**in accordance with 17.5.2.1 as well as for the equations in 17.5.2.1 through 17.5.2.8 shall not exceed the largest of:**

*A*_{Vc}(a) ** c_{a}_{2} /1.5**, where

**is the largest edge distance**

*c*_{a}_{2}(b) *h _{a}* /1.5

(c) ** s/3**, where

**is the maximum spacing perpendicular to direction of shear, between anchors within a group**

*s***ψ**, shall be calculated as

_{ec,V}(17.5.2.5) |

but **ψ _{ec,V}** shall not be taken greater than 1.0.

If the loading on an anchor group is such that only some anchors are loaded in shear in the same direction, only those anchors that are loaded in shear in the same direction shall be considered when determining the eccentricity of ** e'_{V}** for use in Eq. (17.5.2.5) and for the calculation of

**according to Eq. (17.5.2.1b).**

*V*_{cbg}ψ_{c,V} = 1.4

For anchors located in a region of a concrete member where analysis indicates cracking at service load levels, the following modification factors shall be permitted:

**ψ _{c,V} = 1.0** for anchors in cracked concrete without supplementary reinforcement or with edge reinforcement smaller than a No. 4 bar

**ψ _{c,V} = 1.2** for anchors in cracked concrete with reinforcement of a No. 4 bar or greater between the anchor and the edge

**ψ _{c,V} = 1.4** for anchors in cracked concrete with reinforcement of a No. 4 bar or greater between the anchor and the edge, and with the reinforcement enclosed within stirrups spaced at not more than 4 in.

**ϕ**. A strength reduction factor of 0.75 shall be used in the design of the anchor reinforcement.

*V*_{n}### Related Code Sections

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*Concrete Breakout Strength of Anchor in Shear*> 17.5.2.4

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*Concrete Breakout Strength of Anchor in Shear*> 17.5.2.6

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*Concrete Breakout Strength of Anchor in Shear*> 17.5.2.8