The intent of this page is to clarify the application of ACI’s Section 17.10.5.3 requirements for the installation of post-installed hold-down anchors using epoxy. Four options are provided for determining the required anchor or attachment strength to protect against non-ductile tensile failure. We will discuss Options A and D, which are generally applicable to hold-down anchors.

A quick summary of Options A and D:

Option A:
  • The concrete-governed strength shall be greater than the steel strength of the anchor.
  • The steel strength shall be taken as 1.2 times the nominal steel strength of the anchor.
  • The concrete-governed strength shall be taken as the nominal strength considering pullout, side-face blowout, concrete breakout, and bond strength as applicable.
  • Anchors shall transmit tensile loads via a ductile steel element with a stretch length of at least 8da unless otherwise determined by analysis.
Option D:
  • Anchors or anchor groups must be designed for the maximum tension obtained from factored load combinations that include seismic loads (E), with the seismic load (Eh) increased by an over-strength factor (Ωo).

Our example is for a:

  • Strength level hold-down force of 2000 lb
  • Normal weight 2500 psi cracked concrete
  • No supplemental edge reinforcement
  • 2×4 stud wall
  • SIMPSON® SET-3G or HILTI® HIT-HY 200

Epoxy Anchor Results For Option A

All values are in strength level unless noted otherwise.
Steel Strength (lb)Bond Strength (lb)Concrete Breakout Failure (lb)
Simpson15732121377903 (Governing)
Hilti15732103457903 (Governing)
ACI's ductility requirements are not met since the governing design strength is not steel.

 

Epoxy Anchor Results For Option D

All values are in strength level unless noted otherwise.
Steel Strength (lb)Bond Strength (lb)Concrete Breakout Failure (lb)
Simpson983359173852 (Governing)
3852/(2.5x1.4)=1100 lb ASD Capacity
Hilti983250433852 (Governing)
3852/(2.5x1.4)=1100 lb ASD Capacity
ACI's ductility requirements  are met since anchors designed for maximum tension force include the over strength factor.
In our opinion, using epoxy anchors at existing footings does not provide any reasonable, code compliant tension force generally required for anchor bolts, and other anchorage methods should be used.