# 17.4.5 *Bond Strength of Adhesive Anchor in Tension*

**of a single adhesive anchor or**

*N*_{a}**of a group of adhesive anchors, shall not exceed**

*N*_{ag}(a) For a single adhesive anchor:

(17.4.5.1a) |

(b) For a group of adhesive anchors:

(17.4.5.1b) |

Factors **ψ_{ec,Na}**,

**ψ**, and

_{ed,Na}**ψ**are defined in 17.4.5.3, 17.4.5.4, and 17.4.5.5, respectively.

_{cp,Na}**is the projected influence area of a single adhesive anchor or group of adhesive anchors that shall be approximated as a rectilinear area that projects outward a distance**

*A*_{Na}**from the centerline of the adhesive anchor, or in the case of a group of adhesive anchors, from a line through a row of adjacent adhesive anchors.**

*c*_{Na}**shall not exceed**

*A*_{Na}**, where**

*nA*_{Nao}*n*is the number of adhesive anchors in the group that resist tension loads.

**is the projected influence area of a single adhesive anchor with an edge distance equal to or greater than**

*A*_{Nao}**:**

*c*_{Na}A = (2_{Nao}c)_{Na}^{2} | (17.4.5.1c) |

where

(17.4.5.1d) |

and constant 1100 carries the unit of lb/in.^{2}

**, shall not exceed**

*N*_{ba}(17.4.5.2) |

The characteristic bond stress **τ _{cr}** shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4.

Where analysis indicates cracking at service load levels, adhesive anchors shall be qualified for use in cracked concrete in accordance with ACI 355.4.

For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at service load levels, **τ _{uncr}** shall be permitted to be used in place of

**τ**in Eq. (17.4.5.2) and shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4.

_{cr}It shall be permitted to use the minimum characteristic bond stress values in Table 17.4.5.2, provided (a) through (e) are satisfied:

(a) Anchors shall meet the requirements of ACI 355.4

(b) Anchors shall be installed in holes drilled with a rotary impact drill or rock drill

(c) Concrete at time of anchor installation shall have a minimum compressive strength of 2500 psi

(d) Concrete at time of anchor installation shall have a minimum age of 21 days

(e) Concrete temperature at time of anchor installation shall be at least 50°F

**Table 17.4.5.2—Minimum characteristic bond stresses ^{[1][2]}**

Installation and service environment | Moisture content of concrete at time of anchor installation | Peak in-service temperature of concrete, °F | τ_{cr}, psi | τ_{uncr}, psi |
---|---|---|---|---|

Outdoor | Dry to fully saturated | 175 | 200 | 650 |

Indoor | Dry | 110 | 300 | 1000 |

^{[1]}Where anchor design includes sustained tension loading, multiply values of τ_{cr} and τ_{uncr} by 0.4.

^{[2]}Where anchor design includes earthquake loads for structures assigned to SDC C, D, E, or F, multiply values of τ_{cr} by 0.8 and τ_{uncr} by 0.4.

**ψ**, shall be calculated as:

_{ec,Na}(17.4.5.3) |

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

If the loading on an adhesive anchor group is such that only some adhesive anchors are in tension, only those adhesive anchors that are in tension shall be considered when determining the eccentricity ** e'_{N}** for use in Eq. (17.4.5.3) and for the calculation of

**according to Eq. (17.4.5.1b).**

*N*_{ag}In the case where eccentric loading exists about two orthogonal axes, the modification factor **ψ _{ec,Na}** shall be calculated for each axis individually and the product of these factors used as

**ψ**in Eq. (17.4.5.1b).

_{ec,Na}**ψ**, shall be calculated as

_{ed,Na}If C ≥ _{a,min}C, then ψ_{Na}ed,Na = 1.0 | (17.4.5.4a) |

If C < _{a,min}C, then _{Na} | (17.4.5.4b) |

**ψ**, shall be calculated as:

_{cp,Na}If C ≥ _{a,min}C, then ψ_{ac}cp,Na = 1.0 | (17.4.5.5a) |

If C < _{a,min}C, then _{ac} | (17.4.5.5b) |

but **ψ _{cp,Na}** determined from Eq. (17.4.5.5b) shall not be taken less than

**, where the critical edge distance**

*c*/_{Na}*c*_{ac}**is defined in 17.7.6. For all other cases,**

*c*_{ac}**ψ**shall be taken as 1.0.

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