All-in-one concrete anchor shear calculator for the USA — calculate steel shear capacity (φVsa), concrete breakout strength in shear (φVcb), pryout strength (φVcp), and minimum edge distance for cast-in and post-installed anchors per ACI 318-19 Chapter 17. Covers single anchors, edge distance correction factors, and governing failure mode identification for US structural and non-structural anchor design.
Select a calculation tab — Steel Shear, Concrete Breakout, or Pryout — all per ACI 318-19 Chapter 17 for single anchors.
A_se,V = net tensile stress area of the anchor bolt — see ASME B1.1 thread tables or anchor mfr. data. Example: 1/2" dia. A307 bolt ≈ 0.142 in²
f_uta ≤ 1.9 × f_ya and ≤ 125,000 psi per ACI 318-19 §17.6.1.2 for ductile steel anchors
Ductile steel: f_uta ≤ 1.9 × f_ya AND elongation ≥ 14% AND reduction in area ≥ 30% per ACI 318-19 §17.2.3
Enter 1 for single anchor — for anchor groups, this calculator computes total group steel shear capacity
V_u = factored shear per anchor from structural analysis (1.2D + 1.6L per ASCE 7 / ACI 318-19 §5.3). Enter 0 to skip demand check.
For SDC C–F, ACI 318-19 §17.10 requires additional ductility checks and limits φ factors for post-installed anchors
c_a1 = distance from anchor centerline to the free concrete edge in the direction of applied shear — the critical dimension controlling breakout
c_a2 = perpendicular edge distance. If c_a2 ≥ 1.5×c_a1 (or no perp. edge), the edge effect factor ψ_ed,V = 1.0
h_a = thickness of the concrete member. Member thickness correction ψ_h,V applies when h_a < 1.5×c_a1
l_e = min(h_ef, 8×d_a) for headed bolts — embedment depth up to 8 anchor diameters governs Vb. Use actual embedment for post-installed.
Nominal anchor shaft diameter — used in the V_b basic breakout strength equation
ACI 318-19 limits f'c to 10,000 psi for normal-weight concrete in Chapter 17 calculations
Use cracked concrete (1.0) unless analysis confirms uncracked conditions at service load in the anchor zone
Enter applied V_u to check φVcb ≥ Vu — leave 0 to calculate capacity only
N_cp = N_cb (single anchor) or N_cbg (group) — calculated per ACI 318-19 §17.6.2 in tension. Use anchor tension breakout calculator for this value.
h_ef = effective embedment depth of the anchor. k_cp = 1.0 for h_ef < 2.5 in., k_cp = 2.0 for h_ef ≥ 2.5 in. per ACI 318-19 §17.6.3
Use φ = 0.55 for seismic design categories C–F when Condition B applies (supplemental reinforcement not provided)
Enter applied V_u to check φVcp ≥ Vu — pryout typically governs for short anchors (< 2.5 in. embedment) loaded away from a free edge
Concrete anchor shear design per ACI 318-19 Chapter 17 (the unified anchor design chapter, formerly Appendix D) establishes the design procedure for all anchors — cast-in-place headed bolts, J-bolts, and post-installed mechanical or adhesive anchors — subject to shear loads parallel to the concrete surface. ACI 318-19 Chapter 17 requires the engineer to check all applicable failure modes and use the lowest capacity as the governing strength. For shear, the three failure modes are steel shear failure at the anchor cross-section, concrete breakout toward the nearest free edge, and pryout failure for short stiff anchors. The design must satisfy φVn ≥ Vu for each mode, where Vu is the factored shear demand from ASCE 7-22 load combinations.
Steel shear (§17.6.1): The anchor shaft yields and fractures in shear — governed by anchor steel area Ase,V and ultimate strength futa. This mode usually governs for large-diameter, deeply embedded anchors far from a free edge. Concrete breakout in shear (§17.6.2): A half-pyramid cone of concrete breaks out toward the nearest free edge — governed by edge distance ca1, member thickness ha, and concrete strength f'c. This mode almost always governs when an anchor is close to a free edge. Pryout (§17.6.3): The anchor pries out a concrete plug on the side opposite the shear direction — governs for short, rigid anchors (hef < 2.5 in.) loaded away from a free edge. ACI 318-19 §17.6 requires the engineer to check all three and use the minimum.
ACI 318-19 Section 17.9.1 requires a minimum edge distance of cmin = max(hef/1.5, 6da, specific anchor product requirements). For post-installed anchors, the manufacturer's ICC-ES evaluated minimum edge distance governs. Critical edge distances for concrete breakout: when ca1 < 1.5×hef, the projected breakout area is reduced below the full cone, dramatically reducing φVcb. The most effective way to increase concrete breakout capacity near an edge is to increase ca1 — moving the anchor further from the free edge increases capacity as ca11.5.
Cast-in anchors (ASTM F1554 headed bolts, hooked bolts, J-bolts, welded headed studs) are placed before concrete placement and develop full ACI 318 strength from the embedded head bearing. Post-installed mechanical anchors (expansion anchors, undercut anchors — ASTM F1554) and adhesive anchors (ASTM C881 epoxy, ASTM E488) are installed in drilled holes after concrete hardens. ACI 318-19 requires post-installed anchors to be qualified per ACI 355.2 (mechanical) or ACI 355.4 (adhesive) with published ICC-ES Evaluation Report values for all failure modes. Post-installed adhesive anchors require special inspection for overhead and sustained tensile load conditions.
For anchors in Seismic Design Categories C–F, ACI 318-19 Section 17.10 imposes additional requirements: (1) anchors must be designed for 1.2× the design seismic shear; (2) post-installed anchors must be classified as Category 1 (for SDC C–F) per ACI 355.2/355.4 with enhanced ductility testing; (3) φ factors are reduced — φ = 0.70 for steel shear (vs. 0.65/0.60 for non-seismic), and φ = 0.55 for concrete breakout in SDC C–F Condition B. Supplementary reinforcement can restore the higher φ factors. Seismic provisions apply to any anchor resisting earthquake effects, including diagonal strut and collector connections.
The complete ACI 318-19 Chapter 17 formula set for all three anchor shear failure modes — in US customary units (inches, pounds, kips). These formulas govern all US structural anchor design for cast-in and post-installed anchors under IBC 2021, ASCE 7-22, and ACI 318-19.
When an anchor is subject to both tension (Nu) and shear (Vu) simultaneously, ACI 318-19 Section 17.8 requires an interaction check. The interaction equation is: (Nua/φNn)5/3 + (Vua/φVn)5/3 ≤ 1.0. A simplified check: if Nua ≤ 0.2×φNn, full shear capacity φVn may be used; if Vua ≤ 0.2×φVn, full tension capacity φNn may be used. This interaction check is separate from and in addition to the individual mode capacity checks. This calculator addresses shear only — perform the combined tension+shear interaction check separately when axial loads are also present.
Pre-calculated steel shear capacity (φVsa) and concrete breakout capacity (φVcb) for common US anchor bolt sizes and edge distances — ASTM F1554 Grade 55 / ASTM A193 B7 steel, f'c = 4,000 psi, normal-weight cracked concrete, no perpendicular edge effects.
| Anchor Dia. | Ase,V (in²) | futa | φVsa (kips) | ca1 = 4" | ca1 = 6" | ca1 = 8" | Typical Use |
|---|---|---|---|---|---|---|---|
| 1/2 in. | 0.142 in² | 120 ksi | 6.1 k | 2.1 k | 3.8 k | 5.9 k | Light equipment, façade clips |
| 5/8 in. | 0.226 in² | 120 ksi | 9.7 k | 2.4 k | 4.4 k | 6.9 k | Equipment pads, sill plates |
| 3/4 in. | 0.334 in² | 120 ksi | 14.4 k | 2.8 k | 5.1 k | 7.9 k | Column base plates, handrails |
| 7/8 in. | 0.462 in² | 120 ksi | 19.9 k | 3.1 k | 5.7 k | 8.9 k | Structural column bases |
| 1 in. | 0.606 in² | 120 ksi | 26.1 k | 3.5 k | 6.4 k | 9.9 k | Heavy structural connections |
| 1-1/4 in. | 0.969 in² | 120 ksi | 41.7 k | 4.0 k | 7.3 k | 11.3 k | Moment frame base plates |
| 1/2 in. | 0.142 in² | 75 ksi | 3.8 k | 2.1 k | 3.8 k | 5.9 k | Light-duty F1554 Gr.36/55 |
ACI 318-19 §17.5.3 defines two conditions: Condition A (supplementary reinforcement present — hairpins or U-bars enclosing the anchor, developed beyond the failure plane) uses higher φ factors (φ = 0.75 for concrete breakout in shear vs. 0.70). Condition B (no supplementary reinforcement) uses the standard lower φ factors. For edge anchors close to a free edge, adding a hairpin reinforcement bar (typically #4 or #5 U-bar behind the anchor) can both raise φ and significantly improve breakout capacity beyond what ACI 318-19 §17.6.2 calculates for plain concrete.
For anchor groups (two or more anchors with spacing ≤ 3ca1), ACI 318-19 §17.6.2.1 requires checking the group concrete breakout capacity Vcbg using the total projected area AVc for the entire group divided by AVc0 for a single anchor, multiplied by the eccentricity factor ψec,V = 1/(1 + 2e'V/(3ca1)) ≤ 1.0, where e'V is the distance between the resultant shear force and the centroid of the anchor group. This calculator is for single anchors only — use ACI 318-19 §17.6.2.1 directly for group design.
ACI 318-19 §17.6.2.1(c) provides a special provision when shear is applied parallel to a free edge rather than toward it: the breakout strength Vcb may be taken as twice the value calculated for shear toward the edge at the same edge distance. This doubles the concrete breakout capacity for parallel-to-edge shear, which is highly beneficial for anchors in concrete walls or edges where shear acts along the wall rather than perpendicular to it — a frequently overlooked provision that can significantly increase design capacity.
Column base plate anchor bolts in the USA are typically ASTM F1554 (Grade 36, 55, or 105) cast-in-place headed bolts or J-bolts. For moment-frame base plates, the anchor shear demand is determined from the column shear V and any amplified seismic forces per AISC 341 and ASCE 7-22. Minimum edge distance per AISC Design Guide 1 (Base Plate and Anchor Rod Design) is typically 5 × da for fabricated base plates. The governing failure mode for column base anchors is usually steel shear or pryout when anchors are centered on the base plate well away from the concrete edge — concrete breakout governs only at slab edges or piers.
US structural engineers use these strategies to maximize concrete anchor shear capacity: (1) Increase ca1 — breakout capacity increases as ca11.5, so doubling edge distance increases breakout by ~2.8×; (2) Add hairpin reinforcement — a #4 or #5 U-bar around the anchor shifts failure from brittle breakout to ductile steel or reinforcement yielding; (3) Use larger anchor diameter — increases steel shear as Ase,V; (4) Increase concrete strength — breakout increases as √f'c; (5) Verify uncracked condition — if the zone around the anchor is demonstrably uncracked under service loads, ψc,V = 1.4 increases breakout by 40%. For edge anchors, increasing ca1 and adding hairpin bars is almost always the most cost-effective solution.
This anchor shear calculator uses simplified single-anchor ACI 318-19 Chapter 17 formulas for preliminary design checks. It does not perform: anchor group design, combined tension-shear interaction (§17.8), adhesive anchor bond strength (§17.6.5), seismic anchor qualification (§17.10), ICC-ES ESR product compliance verification, supplementary reinforcement design (Condition A), concrete side-face blowout (§17.6.4), anchor group eccentricity factor (ψ_ec,V), or AISC base plate design per Design Guide 1. All US structural anchor designs must be designed, detailed, and stamped by a licensed Professional Engineer (PE) per ACI 318-19 Chapter 17, IBC 2021, and all applicable state and local codes. Post-installed anchors require ICC-ES Evaluation Service Reports (ESR) confirming qualification per ACI 355.2 or ACI 355.4 for the specific installation conditions.
Official ACI, AISC, and ICC codes and references for US concrete anchor shear design
ACI 318-19 Chapter 17 is the primary US standard governing all concrete anchor design — cast-in and post-installed, for all failure modes in tension and shear. It replaced ACI 318 Appendix D in the 2014 edition and is referenced by IBC 2021 as the mandatory anchor design standard for all US structural and non-structural anchors in reinforced concrete.
Visit ACI.orgAISC Design Guide 1 (Base Plate and Anchor Rod Design, 2nd Edition) provides comprehensive guidance for US column base plate and anchor bolt design, integrating ACI 318 Chapter 17 anchor provisions with AISC 360 steel design. It covers anchor rod sizing, edge distance requirements, grout pad design, shear lug design, and seismic considerations for moment and braced frame base plates.
Visit AISC.orgICC Evaluation Service (ICC-ES) publishes Evaluation Service Reports (ESRs) for post-installed anchor products, confirming compliance with ACI 355.2 (mechanical anchors) or ACI 355.4 (adhesive anchors). ESR reports contain product-specific characteristic strengths, minimum edge distances, embedment depths, and installation requirements that supplement or modify the ACI 318-19 Chapter 17 calculated values for specific proprietary anchor products.
Visit ICC-ES.org