Concrete Headed-Anchor Pullout (ACI 318-19 17.6.3)
Anchor pullout in tension - the head crushing through the concrete.
Example
You enter
- Head/nut net bearing area Abrg (in²) 0.654
- Concrete strength f'c (psi) 4000
- Concrete condition at service cracked
You get
- Basic pullout Np 20928 lb (20.9 kip)
- Design pullout phiNpn 14650 lb (14.6 kip)
Details, formula, and sources
Np = 8 x Abrg x f'c; Npn = psi_cP x Np (1.4 uncracked, 1.0 cracked); phiNpn = 0.70 x Npn. A 3/4-in headed bolt (0.654-in^2 head) in 4,000-psi cracked concrete pulls out at a factored 14.6 kip - and unlike breakout it does not depend on embedment, so deepening the anchor does not raise it. Headed anchors only (not adhesive or expansion). A design check, not a stamped anchor design.
Np = 8 x head_bearing_area_in2 x fc_psi; Npn = psi_cP x Np (psi_cP = 1.4 uncracked at service, 1.0 cracked); phiNpn = 0.70 x Npn.
The ACI 318-19 Section 17.6.3 headed-anchor pullout in tension, by name.
ACI 318 is available through ACI; the 17.6.3 pullout provisions are published design equations.
Estimate. AHJ and licensed professional govern.
Field names used by the API: head_bearing_area_in2, fc_psi, cracking, np_lb, phi_npn_lb
- Embedment-independent pullout Np = 8 Abrg f'c depends on the head area, not the embedment depthACI 318-19 17.6.3.2
- Uncracked bonus psi_cP = 1.4 only when analysis shows the concrete stays uncracked at service; else 1.0ACI 318-19 17.6.3.3