Cast-In Anchor Tension Concrete Breakout (ACI 318-19 Ch. 17)
Concrete breakout capacity of a headed anchor in tension by the ACI 318-19 CCD method.
Example
You enter
- Effective embedment hef (in) 6
- Concrete strength f'c (psi) 4000
- Nearest edge distance ca1 (in, large = away) 100
- Anchor type cast-in
- Lightweight factor lambda 1
You get
- Basic breakout Nb 22308 lb
- Design capacity phiNcb 15616 lb
Details, formula, and sources
Nb = kc lambda sqrt(f'c) hef^1.5 (kc 24 cast-in / 17 post-installed), edge-modified to Ncb and design phiNcb. The hef^1.5 cone and near-edge knockdown that anchor-embedment never checks; a near edge can cut capacity 25% before the steel yields.
Nb = kc lambda sqrt(f'c) hef^1.5 (kc 24 cast-in, 17 post-installed); ANco = 9 hef^2; psi_ed = 0.7 + 0.3 ca1/(1.5 hef) when ca1 < 1.5 hef; Ncb = (ANc/ANco) psi_ed Nb; phiNcb = 0.70 Ncb (Condition B, no supplementary reinforcement).
The ACI 318-19 Section 17.6.2 concrete breakout strength in tension (CCD method), by name.
ACI 318 is readable free through the ACI online reading room at concrete.org; the Chapter 17 anchoring provisions are in the published code.
Estimate. AHJ and licensed professional govern.
Field names used by the API: embedment_in, fc_psi, edge_distance_in, anchor_type, lambda, nb_lb, phi_ncb_lb
- kc constant 24 cast-in, 17 post-installed (CCD basic-strength coefficient)ACI 318-19 17.6.2.2
- Projected area ANco = 9 hef^2; a full breakout cone needs 1.5 hef of edge on all sidesACI 318-19 17.6.2.1
- psi_c cracked factor taken as 1.0 (cracked); an uncracked section with supplementary reinforcement raises itACI 318-19 17.6.2.6