Cast-In Headed Anchor in Concrete (ACI 318 Ch. 17)
Strength design of a single cast-in headed anchor in concrete per ACI 318-19 Chapter 17, loaded in tension and shear. Evaluates all tension failure modes (steel, concrete breakout, pullout), all shear failure modes (steel, concrete breakout toward the edge, pryout), side-face blowout where applicable, and the combined tension-shear interaction. Uses the deep-embedment alternative for the basic breakout strength where applicable. Single anchor only — groups, corners, thin members, post-installed/adhesive anchors, and seismic are excluded. Fully customizable.
What this calculates
Steel tensile strength (Nsa), concrete breakout strength in tension (Ncb) from the basic breakout Nb with modification factors, pullout strength (Npn), the governing design tension strength (φNn); steel shear strength (Vsa), concrete breakout in shear toward edge ca1 (Vcb), pryout strength (Vcp), the governing design shear strength (φVn); and the Section 17.8 tension-shear interaction ratio.
Inputs
Nominal bolt diameter
Effective tensile/shear stress area
Net bearing area of the anchor head
Specified tensile strength, ≤ min(1.9·fya, 125 ksi)
Effective embedment depth
Specified compressive strength of concrete
Edge distance toward which shear acts
Factored tensile demand on the anchor
Factored shear demand on the anchor
Outputs
Governing design tension strength (steel/breakout/pullout)
Governing design shear strength (steel/breakout/pryout)
Tension demand-to-capacity ratio
Shear demand-to-capacity ratio
Combined tension-shear interaction per §17.8 — must be ≤ 1.0
Methodology
Per ACI 318-19 Chapter 17 (strength design), single cast-in headed anchor in normalweight concrete (λa = 1.0). φ factors are Condition B, no supplementary reinforcement (Table 17.5.3): steel tension 0.75, steel shear 0.65, concrete (breakout/pullout/pryout) 0.70. Tension breakout uses the basic breakout Nb with kc = 24 for cast-in anchors (Section 17.6.2.2.1), switching to the deep-embedment alternative Nb = 16·λa·√f'c·hef^(5/3) for 11 in ≤ hef ≤ 25 in (Section 17.6.2.2.3). Side-face blowout (Section 17.6.4) is applied when hef > 2.5·ca1. Tension-shear interaction per Section 17.8. Assumes tension not edge-controlled and shear toward one edge with other edges far.
Code References
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