Detail Categories (EN 1993-1-9 Tables 8.1-8.10)

Category Description Typical Application
160 Base metal, rolled sections away from welds Plain girder
140 Base metal with welded attachments, short Beam with short stiffeners
125 Full penetration butt weld, ground flush Welded splices ground smooth
112 Full penetration butt weld, NDT checked Welded splices
100 Fillet welded attachment Cross-beam connections
90 Fillet welded cover plate end Cover plate termination
80 Longitudinal weld of stiffener Stiffener-to-web weld
71 Fillet weld, transverse load, K-joint Truss K-joints, crane girders
63 Cruciform joint with partial penetration Heavy welded sections
56 Transverse butt weld on backing bar Site welds
50 Base metal at weld toe of stiffener Fillet welded stiffener toe
45 Base metal at end of welded cover plate Cover plate end on flange
40 Base metal at fillet weld on edge plate Edge beam weld termination
36 Non-load-carrying longitudinal fillet weld Longitudinal attachments

S-N Curves (EN 1993-1-9 Table 8.1)

Category Delta_sigma_C (MPa) at 2M cycles Delta_sigma_D (MPa) at 5M cycles Delta_sigma_L (MPa) at 100M cycles
160 160 118 65
140 140 103 57
125 125 92 51
112 112 83 46
100 100 74 40
90 90 66 36
80 80 59 32
71 71 52 29
63 63 46 26
56 56 41 23
50 50 37 20
45 45 33 18
40 40 29 16
36 36 26 15

For constant amplitude stress ranges above Delta_sigma_D, slope m = 3. Below Delta_sigma_D, slope m = 5. Stress ranges below Delta_sigma_L do not contribute to fatigue damage.

Partial Factors (EN 1993-1-9 Table 3.1)

Assessment Method gamma_Ff gamma_Mf
Damage tolerant (low consequence) 1.00 1.00
Safe life (medium consequence) 1.00 1.15
Fail safe — non-welded details 1.00 1.15
Fail safe — welded details 1.00 1.25

Worked Example — Crane Runway Girder

Welded plate girder, 12 m span. Detail category at web-to-flange weld: Category 71. Crane: 100 kN capacity, 5000 cycles/day, 50 year design life (approx 1.25M cycles).

Stress range at weld: Delta_sigma = 90 MPa (tension to near-zero)

Parameter Value
Category 71
Delta_sigma_C 71 MPa
Applied Delta_sigma 90 MPa
gamma_Ff 1.00
gamma_Mf 1.25

Fatigue resistance: Delta_sigma_C / gamma_Mf = 71 / 1.25 = 56.8 MPa Applied: gamma_Ff x Delta_sigma = 1.00 x 90 = 90 MPa > 56.8 MPa

Fatigue life: N_Rd = 2E6 x (71 / 90)^3 = 2E6 x 0.491 = 982,000 cycles Design life: 1.25M cycles > 982k cycles — detail does NOT achieve design life.

Option: Upgrade to Category 100 (ground butt weld): N_Rd = 2E6 x (100 / 90)^3 = 2E6 x 1.372 = 2.74M cycles > 1.25M cycles OK

Design Applications

Common Design Scenarios

This reference covers structural design scenarios commonly encountered in structural steel design practice:

Related Design Considerations

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:

  1. Determine governing load combination (ULS or SLS per EN 1990)
  2. Calculate maximum internal forces (moment, shear, axial)
  3. Compute nominal capacity per code provisions
  4. Apply resistance/safety factors
  5. Verify interaction if combined forces exist

Result: Use the results from the Steel Calculator tool to verify design adequacy.

Frequently Asked Questions

What European Standard governs structural steel design?

EN 1993 (Eurocode 3: Design of Steel Structures) is the primary standard for structural steel design in Europe. EN 1993-1-1 covers general rules for buildings, EN 1993-1-8 addresses connection design, and EN 1993-1-2 covers fire design. The standard uses limit state design with partial safety factors (γM). National Annexes adapt parameters to each member state. Companion standards include EN 10025 for hot-rolled products, EN 1090 for execution, and EN 1994 for composite design.

What are the common steel grades used in European construction?

The most common steel grades for European construction are S235, S275, S355, S420, and S460 per EN 10025-2. S355 (minimum yield 355 MPa for t ≤ 16 mm) is the most widely used for structural applications. S275 is used for secondary members. S420 and S460 are quenched and tempered high-strength steels for weight-critical applications. Weathering steel (S355J2W) and fine-grain structural steels (EN 10025-3 and -4) are also available.

How does EN 1993 compare to other international steel design codes?

EN 1993, AISC 360 (US), AS 4100 (Australia), and CSA S16 (Canada) all use limit states design principles but differ in key details. EN 1993 uses partial safety factors (γM0 = 1.00, γM1 = 1.00, γM2 = 1.25) rather than resistance factors (φ). Buckling curves in EN 1993 follow the European Column Curve system (a0 to d) with 5 distinct curves, compared to AISC's single curve. EN 1993-1-8 has comprehensive connection design provisions including the component method for moment connections.

Frequently Asked Questions

What do the detail categories in EN 1993-1-9 represent?

Detail categories (Delta_sigma_C) represent the fatigue strength at 2 million cycles. Higher numbers (160 for plain rolled sections) indicate better fatigue performance. Lower numbers (36 for longitudinal fillet welds) indicate fatigue-sensitive details. The category depends on geometry, loading direction, weld type, and fabrication quality.

How does the Palmgren-Miner rule apply?

The Palmgren-Miner rule (Clause 8.3) sums fatigue damage: D = sum(n_i / N_Ri) where n_i is cycle count at stress range Delta_sigma_i and N_Ri is the endurance from the S-N curve. Failure when D >= 1.0. For variable amplitude loading, the stress spectrum is binned and damage accumulated. EN 1993-1-9 permits using equivalent constant amplitude stress range for simplified assessment.

Related Pages

Educational reference only. Fatigue design per EN 1993-1-9:2005. Detail categories from Tables 8.1-8.10. Verify fatigue load models with EN 1991 parts. Results are PRELIMINARY - NOT FOR CONSTRUCTION without independent verification.

Design Resources

Reference pages