Anchor Spacing, Edge Distance & Embedment Depth Flashcards

For a single adhesive anchor loaded in tension, the failure mode most sensitive to insufficient edge distance is:

Answer: Concrete side-face blowout or edge breakout

Insufficient edge distance leads to concrete side-face blowout or concrete edge breakout failure, where the concrete cone or wedge breaks away toward the free surface.

When the concrete member thickness is exactly equal to the minimum required thickness for the specified embedment depth, the installer should:

Answer: Proceed normally because the minimum thickness requirement is satisfied

The minimum member thickness requirement exists precisely to define the boundary condition — meeting the minimum exactly is acceptable per the product evaluation report.

When anchor rods are installed in a rectangular pattern (group anchorage), the 'anchor influence area' concept is used to:

Answer: Calculate the projected failure area for concrete breakout capacity of the group

The anchor influence area (A_Nc) is the projected area of the concrete failure cone for a group of anchors, used to calculate reduced group concrete breakout capacity in tension.

An installer is directed to place anchors at 3d_a edge distance where d_a is the anchor rod diameter. This is most likely the:

Answer: Minimum permitted edge distance below which installation is not allowed

3d_a is a common minimum edge distance value representing the absolute lower limit below which anchor installation is prohibited, not the value for full capacity.

Which situation would most likely require the engineer of record to recalculate anchor capacity using reduced edge distance modification factors?

Answer: Anchors installed between the minimum and critical edge distances

When the actual edge distance falls between the minimum and critical values, ACI 318 requires applying modification factors (ψ_ed,N and ψ_ed,V) that reduce calculated capacity.

The manufacturer's printed installation instructions (MPII) for an adhesive anchor system specify a minimum embedment depth of 4 inches. The engineer has specified 3.5 inches for a particular application. The installer should:

Answer: Install at 4 inches per the MPII and notify the engineer of the discrepancy

The installer must follow the MPII minimum requirements and immediately notify the engineer of record of the discrepancy so the design can be reviewed and corrected.

In seismic design categories C through F, post-installed adhesive anchors used for structural connections must meet which additional qualification requirement beyond basic ACI 318 provisions?

Answer: Anchors must be qualified for seismic applications through testing per ACI 355.4 or ICC-ES AC308 seismic protocols

For seismic design categories C–F, ACI 318 requires that post-installed adhesive anchors be qualified for seismic use through specific cyclic load testing per ACI 355.4 or ICC-ES AC308.