EN 1993 Bolt Spacing & Edge Distance — Eurocode 3 Table 3.3
Complete reference for minimum and maximum bolt spacing and edge distances per EN 1993-1-8:2005 Table 3.3. Requirements for standard round holes, oversize holes, and slotted holes in European structural connections.
Quick access: Bolt Bearing & Tearout → | Bolt Torque Chart → | Bolt Group Capacity →
Minimum Spacing and Edge Distances — Table 3.3
| Parameter | Symbol | Minimum | Maximum |
|---|---|---|---|
| End distance (loaded toward end) | e₁ | 1.2 × d₀ | 4t + 40 mm |
| Edge distance (perpendicular) | e₂ | 1.2 × d₀ | 4t + 40 mm |
| Spacing parallel to load (between bolt rows) | p₁ | 2.2 × d₀ | min(14t, 200 mm) |
| Spacing perpendicular to load (between bolt lines) | p₂ | 2.4 × d₀ | min(14t, 200 mm) |
| Spacing in any direction | p₁, p₂ | — | min(14t, 200 mm) |
Where d₀ = hole diameter and t = the minimum plate thickness.
Minimum Values by Bolt Size
| Bolt Size | d₀ (std) | e₁/e₂ min | p₁ min | p₂ min |
|---|---|---|---|---|
| M12 | 13.5 | 17 mm | 30 mm | 33 mm |
| M16 | 18.0 | 22 mm | 40 mm | 44 mm |
| M20 | 22.0 | 27 mm | 49 mm | 53 mm |
| M22 | 24.0 | 29 mm | 53 mm | 58 mm |
| M24 | 26.0 | 32 mm | 58 mm | 63 mm |
| M27 | 30.0 | 36 mm | 66 mm | 72 mm |
| M30 | 33.0 | 40 mm | 73 mm | 80 mm |
| M36 | 39.0 | 47 mm | 86 mm | 94 mm |
Standard practice for M20: e₁ = e₂ = 30-40 mm, p₁ = 60-80 mm, p₂ = 60-80 mm.
Maximum Spacing Requirements
The maximum limits prevent plate buckling between bolts in compression zones:
- Maximum p₁ = min(14 × t_comp, 200 mm) — parallel to load
- Maximum p₂ = min(14 × t_comp, 200 mm) — perpendicular to load
- Maximum e₁, e₂ = 4 × t + 40 mm
For a 10 mm thick compression plate:
- Maximum p₁ = min(14 × 10, 200) = 140 mm
- Maximum e₁ = 4 × 10 + 40 = 80 mm
For a 20 mm thick plate:
- Maximum p₁ = min(14 × 20, 200) = 200 mm (capped)
- Maximum e₁ = 4 × 20 + 40 = 120 mm
Special Hole Types — Clause 3.6.2
Oversize Holes
| Bolt Size | Standard d₀ | Oversize d₀ | Spacing Adjustment |
|---|---|---|---|
| M12 | 13.5 | 15 | p₁ + 1.5 mm |
| M16 | 18 | 20 | p₁ + 2.0 mm |
| M20 | 22 | 24 | p₁ + 2.0 mm |
| M24 | 26 | 28 | p₁ + 2.0 mm |
| M30 | 33 | 36 | p₁ + 3.0 mm |
Oversize holes are used in slip-resistant connections to facilitate erection tolerances.
Short Slotted Holes
For short slotted holes (parallel to load direction), increase p₁ by the slot length minus the standard clearance.
Edge Distance and Spacing — Practical Guidance
Standard Connection Layouts
| Connection Type | Recommended p₁ | Recommended e₁ | Recommended p₂ | Recommended e₂ |
|---|---|---|---|---|
| End plate (beam depth) | 70 mm | 40 mm | — | 35 mm |
| Fin plate (simple) | 60 mm | 35 mm | 60 mm | 35 mm |
| Gusset plate (brace) | 70 mm | 35 mm | 60 mm | 35 mm |
| Column splice | 80 mm | 40 mm | 80 mm | 40 mm |
| Base plate | 100-150 mm | 50-75 mm | 100-150 mm | 50-75 mm |
Corrosion and Fire Protection Allowance
For galvanized connections, add 3 mm to all edge distances to account for the galvanizing coating thickness. For fire-protected connections, ensure adequate clearance for fireproofing.
Design Applications
Common Design Scenarios
This reference covers structural design scenarios commonly encountered in structural steel design practice:
- Strength verification: Check member or connection capacity against factored loads per the applicable design code
- Serviceability checks: Verify deflections, vibrations, and other serviceability criteria
- Code compliance: Ensure design meets all provisions of the governing standard
- Connection detailing: Verify weld sizes, bolt quantities, and edge distances
Related Design Considerations
- System behavior: consider the interaction between members and connections
- Load paths: verify that forces can be transferred through the structure to the foundations
- Constructability: check that the design can be fabricated and erected practically
- Cost optimization: evaluate alternative sections or connection types for economy
Worked Example
Problem: Verify a typical steel member for the following conditions:
Typical span: 6.0 m | Load: service loads per applicable code | Section: common section in this category
Design Check:
- Determine governing load combination (LRFD or ASD per applicable code)
- Calculate maximum internal forces (moment, shear, axial)
- Compute nominal capacity per code provisions
- Apply resistance/safety factors
- Verify interaction if combined forces exist
Result: Use the results from the Steel Calculator tool to verify design adequacy.
Frequently Asked Questions
What Australian Standard governs structural steel design?
AS 4100-2020 (Steel Structures) is the primary standard for structural steel design in Australia. It covers all aspects of design including member capacity, connections, serviceability, and fire resistance. The standard uses a limit states design philosophy with resistance factors (φ) applied to nominal capacities. Companion standards include AS/NZS 3679.1 for hot-rolled sections, AS/NZS 1554 for welding, and AS/NZS 4600 for cold-formed steel.
What are the common steel grades used in Australian construction?
The most common steel grades for Australian construction are Grade 300 and Grade 350 per AS/NZS 3679.1. Grade 300 (minimum yield 300 MPa for sections > 12 mm thick) is the standard for general structural applications. Grade 350 (minimum yield 340 MPa for sections > 12 mm) is used where higher strength reduces weight. Grade 400 and Grade 450 are available for specialized applications requiring higher strength-to-weight ratios.
How does AS 4100 compare to AISC 360?
Both AS 4100 and AISC 360 use limit states design (LRFD) principles. Key differences include: AS 4100 uses a single "capacity factor" φ approach rather than separate φ for different failure modes; AS 4100 specifies distinct buckling curves for hot-rolled and welded sections; the moment capacity formula in AS 4100 uses αm factor directly rather than Cb; and AS 4100 has more detailed provisions for slender sections and combined actions. Despite philosophical differences, both codes produce similar results for typical members.
Frequently Asked Questions
What is the minimum edge distance for M20 bolts per EN 1993-1-8?
The minimum edge distance e₁ and e₂ for M20 bolts (d₀ = 22 mm) is 1.2 × 22 = 26.4 mm. In practice, use 30 mm minimum for standard details. For base plates with large anchor plates, 40-50 mm is more common.
Can I use bolt spacing less than the minimum per Table 3.3?
Per EN 1993-1-8 Clause 3.5(1), the minimum values in Table 3.3 are mandatory for design. Reduced spacing leads to reduced bearing resistance (lower α_b and k₁ factors) and increased risk of block shear failure. Spacing below 2.2 × d₀ is not permitted for structural connections.
Related Pages
- Bolt Bearing & Tearout — Bearing per EN 1993-1-8 Clause 3.6
- Bolt Group Capacity — Eccentric loads
- Bolt Torque Chart — Torque-tension values
- End Plate Connection — Moment connection
- All European References
Educational reference only. Spacing requirements per EN 1993-1-8:2005 Table 3.3. Verify against project specification and National Annex requirements. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification.
Design Resources
Calculator tools
- Bolt Torque Calculator
- Bolted Connection Calculator
- Splice Connection Calculator
- Steel Bolted Connection Calculator
Design guides