Wedge Anchor Pull-Out Strength & Load Tables
Wedge anchor pull-out strength is the tension load (lbf) at which an anchor will fail by being pulled out of the concrete. Together with shear capacity (lateral load), these are the two core design values an engineer needs to specify a wedge anchor for any structural, equipment, or code-required installation. This guide provides published tension and shear values for the Simpson Strong-Tie Strong-Bolt 2 across all six standard diameters in carbon steel and stainless steel, plus design guidance on combining loads, edge distance effects, and concrete condition factors.
Single-page printable reference with the same load values shown below, plus edge distance, spacing, code listings, and material strength properties. Drop into your project submittal package.
In This Guide:
- What Is Pull-Out Strength?
- Tension Load Values (Steel Strength)
- Shear Load Values (Steel Strength)
- Combined Tension & Shear Loading
- Concrete Strength & Cracked vs Uncracked
- Edge Distance & Spacing Effects
- Sample Design Calculation
- Carbon Steel vs Stainless Steel Loads
- Frequently Asked Questions
What Is Wedge Anchor Pull-Out Strength?
Pull-out strength is the maximum tension load an anchor can resist before failing. For a wedge anchor, “failure” can occur in three different modes depending on the installation conditions:
- Steel failure (N_sa): the anchor body itself yields or fractures in tension. This is the upper bound of what a perfectly-installed anchor in adequate concrete can carry.
- Concrete breakout failure (N_cb): a cone of concrete pulls out of the substrate around the anchor. Governed by concrete strength, embedment depth, and edge distance.
- Pullout failure (N_p): the wedge clip slips through its expansion zone inside the hole. Governed by hole quality, concrete density, and torque-up condition.
Engineers must verify the anchor is adequate against the LOWEST of these three failure modes for their specific application. The published “steel strength” values (the most commonly referenced numbers) represent the upper bound; concrete breakout and pullout failures may govern at smaller edge distances, weaker concrete, or shallower embedment. For code-required design, follow ACI 318 Chapter 17 or the manufacturer’s ESR evaluation report.
Wedge Anchor Tension Load Values — Steel Strength
The values below are steel-strength (N_sa) values per ACI 318-19 17.6.1 for the Simpson Strong-Bolt 2. These are the published catalog values WITHOUT code-required reduction factors applied — for design loads, multiply by the appropriate strength reduction factor (φ) and divide by the load combination per ACI 318.
| Anchor Diameter | Carbon Steel (N_sa) | Type 304/316 Stainless (N_sa) | Strength Reduction Factor (φ_sa) |
|---|---|---|---|
| 1/4" | 2,225 lbf | 3,060 lbf | 0.75 |
| 3/8" | 5,600 lbf | 5,140 lbf | 0.75 |
| 1/2" | 12,100 lbf | 12,075 lbf | 0.75 |
| 5/8" | 19,070 lbf | 17,930 lbf | 0.75 |
| 3/4" | 29,700 lbf | 25,650 lbf | 0.75 |
| 1" | 36,815 lbf | (N/A) | 0.75 |
Source: Simpson Strong-Tie catalog C-A-2023, pages 100 (carbon steel) and 114 (stainless steel). Values are catalog reference values for design comparison. For concrete breakout and pullout values, which may govern at smaller edge distances or shallower embedments, see ICC-ES ESR-3037.
Wedge Anchor Shear Load Values — Steel Strength
Shear values (V_sa) per ACI 318-19 17.7.1 represent the lateral load capacity at the upper embedment depth available for each diameter. Shorter embedments produce lower values; see Simpson’s full design tables for the per-embedment breakdown.
| Anchor Diameter | Carbon Steel (V_sa) | Type 304/316 Stainless (V_sa) | Strength Reduction Factor (φ_sa) |
|---|---|---|---|
| 1/4" | 965 lbf | 1,605 lbf | 0.65 |
| 3/8" | 1,800 lbf | 3,085 lbf | 0.65 |
| 1/2" | 5,285 lbf | 7,245 lbf | 0.65 |
| 5/8" | 7,235 lbf | 10,760 lbf | 0.65 |
| 3/4" | 11,035 lbf | 12,765 lbf | 0.65 |
| 1" | 14,480 lbf | (N/A) | 0.65 |
Source: Simpson C-A-2023, pages 101 (carbon) and 115 (stainless). Stainless shear values exceed carbon steel at smaller diameters because of higher tensile strength of the stainless alloys; carbon steel surpasses stainless at larger diameters.
Combined Tension & Shear Loading
Most real-world installations subject the anchor to BOTH tension and shear simultaneously. For example, a base plate carrying a column with eccentric load experiences uplift (tension) and horizontal force (shear) at the same time. Per ACI 318-19 17.8, combined loading is evaluated using an interaction equation:
Where:
- N_ua = factored applied tension load
- V_ua = factored applied shear load
- φN_n = design tension capacity (steel, breakout, or pullout, whichever governs)
- φV_n = design shear capacity (steel, breakout, or pryout, whichever governs)
This is more conservative than a linear interaction (N/N_n + V/V_n ≤ 1.0) and reflects the non-linear behavior of anchors under combined loading. For design, use the engineering reference PDF or full Simpson ESR-3037 tables.
Concrete Strength & Cracked vs Uncracked Concrete
The pullout and concrete breakout components of wedge anchor capacity scale with the square root of concrete compressive strength (f′_c). Higher-strength concrete produces higher anchor capacity. Common conditions:
| Concrete Strength | Typical Application | Capacity Effect vs 4000 psi |
|---|---|---|
| 2,500 psi | Low-grade structural slab | ~79% of 4000 psi values |
| 3,000 psi | Standard interior slab | ~87% |
| 4,000 psi | Most common structural concrete (baseline) | 100% |
| 5,000 psi | Higher-grade structural slabs, tilt-up panels | ~112% |
| 6,000 psi | High-rise structural elements | ~122% |
Cracked vs Uncracked Concrete
ACI 318 distinguishes between cracked and uncracked concrete because anchor capacity differs significantly between the two conditions. Most concrete in service IS cracked (cracks form due to thermal cycling, shrinkage, applied loads, or seismic events), so modern code-listed anchors must be qualified for both states.
- Uncracked concrete: Anchor zone has no cracks intersecting the embedment. Higher pullout values. Typical of new pours in protected interior environments.
- Cracked concrete: Cracks may pass through the anchor zone. Reduced pullout values, typically 60-70% of uncracked. Default assumption for most design work unless analysis confirms uncracked conditions.
The Simpson Strong-Bolt 2 is qualified for BOTH cracked and uncracked concrete per ICC-ES ESR-3037, which is one of the reasons it's the default choice for code-required structural installations. Some older or budget wedge anchors are qualified only for uncracked concrete — verify before specifying.
Edge Distance & Spacing Effects on Capacity
When a wedge anchor is installed close to a concrete edge or close to another anchor, its tension capacity reduces because the concrete breakout cone is partially missing. Simpson’s ESR-3037 provides reduction factors and minimum dimensions; the simplified version below shows the critical edge distance (c_ac, the distance at which capacity is NOT reduced) and minimum edge distance (c_min, the absolute closest the anchor can be to an edge).
| Diameter | Critical Edge Distance (c_ac) | Min. Edge Distance (c_min) | Min. Spacing (s_min) |
|---|---|---|---|
| 1/4" | 2-1/2" | 1-3/4" | 2-1/4" |
| 3/8" | 6-1/2" | 6" | 3" |
| 1/2" | 6" | 6" | 2-3/4" |
| 5/8" | 7-1/2" | 6-1/2" | 5" |
| 3/4" | 6" | 4-1/4" | 3-1/2" |
| 1" | 13-1/2" | 8" | 8" |
If your installation requires anchors closer to an edge than c_ac, apply the linear reduction factor from c_min to c_ac (per ESR-3037 tables). At c_min, capacity reductions can reach 50% or more on tension, less on shear. Closer than c_min is not permitted.
Sample Design Calculation
Application: Mounting a steel base plate with 4 anchors carrying 8,000 lbf tension and 5,000 lbf shear distributed equally. Concrete is 4,000 psi uncracked. No edge distance constraints.
- Per-anchor demand: 8,000 / 4 = 2,000 lbf tension; 5,000 / 4 = 1,250 lbf shear
- Try 1/2" Strong-Bolt 2 carbon steel:
- N_sa = 12,100 lbf, φ_sa = 0.75 → φN_n = 9,075 lbf design tension capacity
- V_sa = 5,285 lbf, φ_sa = 0.65 → φV_n = 3,435 lbf design shear capacity
- Combined loading check: (2,000 / 9,075)5/3 + (1,250 / 3,435)5/3 = 0.067 + 0.142 = 0.209 ≤ 1.0 ✓
- Result: 1/2" Strong-Bolt 2 in 4,000 psi uncracked concrete with adequate edge distance is more than sufficient for this load. Designer may also check 3/8" for cost optimization.
This sample is illustrative only. Real designs must include load combinations per applicable building code, concrete breakout and pullout capacity checks, edge distance reduction factors, and seismic adjustments where applicable. Always verify against the current ICC-ES ESR-3037 and your project-specific load combinations.
Carbon Steel vs Stainless Steel — Load Capacity Comparison
Stainless steel wedge anchors generally carry LOWER tension values than carbon steel of the same diameter because stainless alloys have lower yield strength. Shear values can be HIGHER for stainless at smaller diameters due to different tensile properties. Use the comparison below for material-tradeoff decisions:
- Where carbon steel wins: larger diameters (3/4", 1"), tension-dominant applications, code-required structural where the highest published values are needed
- Where stainless wins: shear-dominant applications at smaller diameters (1/4", 3/8"), exterior/marine/coastal/chemical environments where corrosion would quickly degrade carbon steel, applications where stainless aesthetics matter
- Where they're similar: mid-size diameters (1/2", 5/8") in tension — values differ by less than 10%, so material decision is driven by environment, not load
For the full material/finish decision logic including 304 vs 316 stainless and mechanically galvanized, see our Wedge Anchor Material & Finish Selection Guide.
Frequently Asked Questions
What is the pull-out strength of a 1/2 inch wedge anchor?
A 1/2" Simpson Strong-Bolt 2 carbon steel wedge anchor has a published steel-strength tension value (N_sa) of 12,100 lbf per ACI 318-19. The 1/2" stainless version has nearly identical 12,075 lbf. These are catalog reference values; actual design capacity is obtained by multiplying by the strength reduction factor (φ_sa = 0.75) and verifying against concrete breakout and pullout limits per ESR-3037.
How much weight will a 5/8 inch wedge anchor hold?
The 5/8" Strong-Bolt 2 carbon steel has 19,070 lbf in tension and 7,235 lbf in shear at steel strength. After applying the 0.75 strength reduction factor for tension and 0.65 for shear, design capacities are roughly 14,300 lbf tension and 4,700 lbf shear in 4,000 psi uncracked concrete with adequate edge distance. For 4,000 psi cracked concrete, expect roughly 60-70% of those values.
What is the difference between cracked and uncracked concrete for anchor design?
Uncracked concrete has no cracks passing through the anchor embedment zone. Cracked concrete has cracks (from thermal cycling, shrinkage, applied loads, or seismic events) that pass through the zone and reduce anchor capacity. Modern code-listed anchors like the Simpson Strong-Bolt 2 are qualified for both conditions. Most design work assumes cracked concrete unless analysis confirms uncracked conditions.
Can I add tension and shear values to get total capacity?
No. Tension and shear interact non-linearly under combined loading. Per ACI 318-19 17.8, use the interaction equation: (N_ua / φN_n)^(5/3) + (V_ua / φV_n)^(5/3) ≤ 1.0. This is more conservative than simple addition and reflects how anchors actually behave under combined load.
Where do I get specific load values for cracked concrete or different embedment depths?
The values shown on this page are steel-strength values at the longer embedment options. For complete tables including concrete breakout, pullout, cracked vs uncracked differentiation, multiple embedment depths, and seismic adjustments, see the official ICC-ES ESR-3037 evaluation report or download our STB2 Engineering Reference Sheet (PDF).
Are the published load values pre-reduced for design?
No. Published catalog and ESR values are nominal capacities without reduction factors. For design loads (LRFD), multiply by the appropriate strength reduction factor (φ) from ACI 318 Chapter 17. For ASD allowable loads, divide by the appropriate factor of safety. Always cross-check against current code editions for any changes.
What is the 5/3 exponent in the interaction equation?
The 5/3 exponent in the ACI 318-19 17.8 interaction equation reflects experimental anchor behavior under combined tension-shear loading. It produces a more conservative envelope than a 1.0 exponent (linear) but less conservative than a 2.0 exponent (circular). All ICC-ES evaluation reports for post-installed anchors use this 5/3 form.
How do edge distance and spacing affect the published load values?
If your installation has edge distance ≥ the critical edge distance (c_ac) and spacing ≥ critical spacing (typically 8 inches), the published full values apply with no reduction. Below c_ac, apply linear reduction factors per ESR-3037 tables. At minimum edge distance (c_min), capacity reductions can reach 50% on tension and somewhat less on shear. Closer than c_min is not permitted under code.
Related Resources
- Wedge Anchor Selection & Installation Guide — sizing, embedment, torque, install steps
- Wedge Anchor vs Sleeve Anchor Comparison — load values compared head-to-head
- Wedge Anchor Material & Finish Selection Guide — carbon steel vs stainless decision aid
- Concrete Anchor Drill Bit & Hole Size Chart
- STB2 Engineering Reference Sheet (PDF) — printable single-page reference
- Shop Simpson Strong-Bolt 2 wedge anchors