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Calculate fastener bearing capacity and allowable loads. Determine if connections can safely support design loads with safety factor checks and material property reference tables.
Using: 1500 psi
Typical range: 2.0 - 5.0
Bearing Area = D × T
Bearing Capacity = Fb × Area × n
Allowable Load = Total Capacity / SF
Where D = fastener diameter, T = thickness, Fb = bearing strength, n = number of fasteners, SF = safety factor
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Bearing capacity is the maximum load that a fastener connection can support before the material crushes or yields under the concentrated stress. It represents the strength of the material in direct contact with the fastener (bolt, rivet, or pin).
Unlike tensile strength, which measures how hard it is to pull material apart, bearing capacity measures how much crushing force the material can withstand in a localized area around a fastener hole.
Bearing Capacity (lbs) = Material Strength × Bearing Area
The bearing capacity calculation involves three simple steps:
Step 1: Area = 0.5 in × 0.25 in = 0.125 sq in
Step 2: Fb = 1500 psi (mild steel)
Step 3: Capacity = 1500 × 0.125 = 187.5 lbs per fastener
Total (4 fasteners) = 750 lbs
Single vs. Double Shear
Single shear: fastener in one plane. Double shear: fastener in two planes. Affects stress distribution.
Material Grade
Different grades of the same material (steel 36, steel 50) have different bearing strengths.
Safety Factor
Always apply a safety factor (typically 2-5) to theoretical capacity.
Typical bearing strength values for common materials and grades:
| Material | Grade/Type | Bearing Strength | Notes |
|---|---|---|---|
| Steel | Mild Steel (A36) | 1,500 psi | Common structural grade |
| Carbon Steel | 2,000 psi | Medium strength | |
| High Strength Steel | 3,000 psi | Heavy-duty applications | |
| Aluminum | 6061-T6 | 1,130 psi | Most common alloy |
| 2024-T4 | 1,480 psi | Aircraft grade | |
| 7075-T6 | 1,940 psi | High strength alloy | |
| Wood | Oak (parallel) | 1,200 psi | Parallel to grain |
| Douglas Fir (parallel) | 800 psi | Common structural lumber | |
| Pine (parallel) | 600 psi | Lower density wood |
Note: Values are typical and may vary based on testing standards and material specifications. Always consult material datasheets for critical applications.
Material crushes or yields directly under the fastener. Occurs when bearing stress exceeds material's bearing strength. Most common failure mode.
Material shears around the fastener hole. Can occur if hole is too large or material strength is low. Results in tearing.
Material tears in tension between fastener holes or at edges. Depends on spacing and edge distance.
Fastener pulls through thin material without bearing stress reaching limit. Occurs with very thin materials or thin washers.
Repeated loading causes micro-cracks that propagate. Design load must be well below bearing capacity for cyclic loading.
A safety factor is applied to reduce theoretical capacity to a safe working load that accounts for uncertainties:
| Application | Safety Factor | Reason |
|---|---|---|
| Static load, known materials | 2.0 - 2.5 | Low uncertainty |
| General building/construction | 3.0 | Standard practice |
| Cyclic/fatigue loading | 4.0 - 5.0 | Higher uncertainty |
| Impact/shock loads | 5.0 - 6.0 | Very conservative |
| Lifting/safety equipment | 8.0 - 10.0 | Life safety critical |
Material properties vary due to manufacturing tolerances, heat treatment variations, and environmental factors.
Actual loads may exceed estimates. Shock loads, impact, and fatigue effects are harder to predict.
Tensile stress is the stress along the length of the material (pulling apart), while bearing stress is the localized crushing stress around a hole or connection point. Bearing stress is typically much higher in a small localized area.
The total bearing capacity is the sum of individual fastener capacities. For identical fasteners in the same material, multiply the single-fastener capacity by the number of fasteners. However, ensure fastener spacing allows each to develop full capacity.
Be careful when mixing standards (AISC, ASME, etc.). Each standard has different assumptions about edge distance, fastener type, and load distribution. Use a consistent standard for your entire design.
If fasteners are too close together, the stress zones overlap, reducing effective capacity. Maintain minimum spacing (typically 2-3x hole diameter) to ensure each fastener can develop full bearing capacity.
These terms are often used interchangeably in bearing capacity calculations. Both refer to stress = Force/Area. Bearing capacity is the maximum stress (force per unit area) that a material can withstand without crushing.
Your connection is limited by whichever is smaller: bearing capacity of the material or shear capacity of the fastener. Both must be checked. This calculator focuses on bearing; separately verify fastener shear strength.
Washers increase the bearing area, which increases capacity. A larger washer area = larger bearing area = higher capacity. This is critical for thin materials where a fastener would otherwise pull through.
Yes. Static loads typically use SF of 2.5-3. Cyclic/fatigue loads require higher factors (4-5) because the stress reduces the material's ability to withstand repeated loading. Impact loads use even higher factors (5-6+).
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