Concrete Anchor Side-Face Blowout (ACI 318-19 17.6.4)
The third headed-anchor tension failure mode, the one deep anchors near an edge actually hit.
Example
You enter
- Nearest edge distance c_a1 (in) 3
- Head/nut net bearing area Abrg (in²) 0.654
- Concrete strength f'c (psi) 4000
- Embedment hef (in) 10
- Lightweight factor lambda_a (1.0 normal weight) 1
You get
- Basic blowout Nsb 24550 lb (24.6 kip)
- Corner factor 1
- Nsbn (lb) 24550.5
- Design phiNsb 17185 lb (17.2 kip)
Details, formula, and sources
Nsb = 160 x c_a1 x sqrt(Abrg) x lambda_a x sqrt(f'c), cut by (1 + c_a2/c_a1)/4 at a corner, phiNsb = 0.70 x Nsb. Governs when hef > 2.5 c_a1 - past that, deepening stops helping and the edge distance is the only knob. The v612 example anchor at a 3 in edge checks 17.2 kip design, and only 10.0 kip in a corner with a 4 in second edge. A design check, not a stamped anchor design.
Nsb = 160 x c_a1 x sqrt(Abrg) x lambda_a x sqrt(f'c); corner modification (1 + c_a2/c_a1)/4 where c_a2 < 3 c_a1; phiNsb = 0.70 x Nsb; governs when hef > 2.5 c_a1.
The ACI 318-19 Section 17.6.4 side-face blowout of a headed anchor in tension, by name.
ACI 318 is available through ACI; the 17.6.4 side-face blowout provisions are published design equations.
Estimate. AHJ and licensed professional govern.
Field names used by the API: edge_distance_in, head_bearing_area_in2, fc_psi, embedment_in, lambda, nsb_lb, corner_factor, nsbn_lb, phi_nsb_lb
- Deep-embedment mode blowout is checked where hef > 2.5 c_a1; the strength scales with the edge distance, not the embedmentACI 318-19 17.6.4.1
- Single anchor closely spaced anchors along the edge (s < 6 c_a1) interact per the group provision, not included hereACI 318-19 17.6.4.2