EN 1993-6 Scope and Application

EN 1993-6:2007 covers the structural design of crane supporting structures — runway beams, gantry girders, and the supporting structure. It works in conjunction with:

• EN 1991-3 — Actions induced by cranes and machinery (load definitions)
• EN 1993-1-1 — General rules for buildings
• EN 1993-1-9 — Fatigue
• EN 1993-1-5 — Plated structural elements (web buckling checks)

The standard applies to overhead travelling cranes (bridge cranes), underslung cranes, and gantry cranes in industrial buildings.

Crane Classification per EN 1991-3

Cranes are classified by duty (severity of use) and load spectrum:

Crane Class — EN 1991-3 Table A.1

Hoist Class (Lifting Application)

Dynamic Factors — EN 1991-3 Clause 2.5

Crane loads are multiplied by dynamic factors to account for inertial effects:

Dynamic Factor φ₂ — Hoisting (Key Factor)

φ₂ = φ₂,min + β₂ × v_h

Where v_h is the hoisting speed in m/s and β₂ depends on the hoist class:

For a typical HC2 workshop crane with v_h = 0.15 m/s: φ₂ = 1.05 + 0.17 × 0.15 = 1.08

Wheel Load Combinations per EN 1991-3

Design wheel loads are combined as groups with associated dynamic factors:

Load Groups — Table 2.2

Where:

• G_c = crane self-weight
• Q_h = hoist (payload) load
• H_L = longitudinal (traction) horizontal force
• H_T = transverse (crab) horizontal force

Crane Induced Actions on the Runway Beam

Vertical Wheel Loads

The maximum static wheel load per end carriage:

Q_r,max = (G_crane/4) + (Q_h/2) × (L_c - a_min) / L_c

Typical 20 t overhead crane (span 20 m, trolley min approach 1.0 m, crane self-weight 12 t):

Q_r,max = (120/4) + (200/2) × (20 - 1.0)/20 = 30 + 100 × 0.95 = 125 kN

With φ₂ = 1.08: Q_r,max,design = 125 × 1.08 = 135 kN

Horizontal Forces

Longitudinal (traction) H_L: H_L = 0.10 × (G_crane × φ₁ + Q_h × φ₂) = 0.10 × (120 × 1.0 + 200 × 1.08) = 33.6 kN

Transverse (crab surge) H_T: H_T = 0.10 × (Q_crab + Q_h) where Q_crab = weight of crab/trolley For a 20 t crane with 3 t crab: H_T = 0.10 × (30 + 200) = 23.0 kN

Runway Girder Design — ULS Checks

Bending (Major Axis) — EN 1993-1-1 Clause 6.2.5

For a simply supported runway beam with two moving wheel loads at spacing a:

Maximum bending moment under a wheel load at mid-span:

M_y,Ed = (ΣQ_r × L / 4) × [1 - a / (2 × L)]²

For two 135 kN wheels at 3.0 m spacing on a 7.5 m span: M_y,Ed = (270 × 7.5/4) × [1 - 3.0/(2 × 7.5)]² = 506.3 × 0.64 = 324.0 kN·m

Lateral-Torsional Buckling — EN 1993-1-1 Clause 6.3.2.1

Crane runway beams are subjected to biaxial bending from vertical plus transverse (lateral) loads. The general method for lateral-torsional buckling:

M_y,Ed / (χ_LT × M_y,Rk / γ_M1) + M_z,Ed / M_z,Rk ≤ 1.0

Where χ_LT is the reduction factor for LTB. Crane runway beams typically have a top flange restrained laterally by the rail, but the bottom flange compression zone near intermediate supports (or over short lengths between restraints) must be checked.

Web Bearing and Buckling — EN 1993-1-5 Clause 6

Under high concentrated wheel loads, the web must be checked for:

1. Local yielding (crushing): F_Rd = f_yw × l_eff × t_w / γ_M0
2. Web buckling (crippling): F_Rd = χ_F × f_yw × l_eff × t_w / γ_M1

The effective loaded length l_eff depends on the rail stiffness and the spread of load through the flange:

l_eff = l_rail + 2 × t_f × (1+f) + b_eff_web

For a 60 kg/m crane rail (head width 72 mm) on a 25 mm flange: l_eff ≈ 72 + 2 × 25 + 5 × (t_f + r) = 72 + 50 + 135 = 257 mm

Fatigue Verification — EN 1993-1-9

Fatigue assessment is mandatory for crane runway girders per EN 1993-6 Clause 9. The equivalent constant amplitude stress range method is used:

Δσ_E2 = λ × Δσ_p ≤ Δσ_C / γ_Mf

Detail Categories for Crane Runway Beams

Damage Equivalent Factors — EN 1993-6 Table 9.1

Worked Example — 20 t Crane Runway Girder

ULS Check Summary

Fatigue Check

Nominal stress range from moving wheel loads: Δσ_p = 135,000 × (7.5/4) / (2,070 × 10³) × 1,000 = 122.3 MPa

Equivalent constant amplitude: Δσ_E2 = 0.793 × 122.3 = 97.0 MPa

For detail category 160 (as-rolled beam, γ_Mf = 1.35): Δσ_C / γ_Mf = 160 / 1.35 = 118.5 MPa > 97.0 MPa — OK

Frequently Asked Questions

What dynamic factors must be applied to crane wheel loads per EN 1991-3?

EN 1991-3 specifies seven dynamic factors φ₁ through φ₇. The most important for ULS design are φ₁ (vibration, applied to crane self-weight), φ₂ (hoisting dynamics, applied to payload), and φ₄ (crane travelling on rails). For a typical workshop crane, φ₂ = 1.05-1.15 for slow hoisting (v_h < 0.25 m/s) and can reach φ₂ = 1.60 for high-speed electric hoists. Load Group 1 (φ₁ × G_c + φ₂ × Q_h) is used for standard ULS design. Load Group 4 (φ₁ × G_c + φ₄ × Q_h) covers fatigue from regular travel.

How does EN 1993-6 address the stability of crane runway beams?

EN 1993-6 requires verification of lateral-torsional buckling per EN 1993-1-1 Clause 6.3.2, considering biaxial bending from vertical wheel loads plus transverse horizontal forces (crab surge). The top flange is typically continuously restrained by the crane rail, so the critical case is often bottom flange compression near the supports (hogging) or between intermediate lateral restraints. Clause 3.3 of EN 1993-6 provides specific guidance for the stability verification of runway beams, including the influence of the rail restraint stiffness.

What fatigue detail category applies to crane runway girders?

Per EN 1993-1-9, the fatigue detail category for an as-rolled runway beam (parent metal near the flange-to-web junction) is Δσ_C = 160 MPa. Welded rail attachments reduce this to 71-80 MPa depending on the weld detail. Transverse web stiffeners create a Category 80 detail at the stiffener-to-flange weld. Full penetration butt welds in the tension flange (splices) are Category 112. The damage equivalent factor λ depends on the load spectrum class, crane classification, and design life — for an HC2 crane with load spectrum S3 and 25-year life, λ ≈ 0.80.

How are horizontal crane forces distributed between runway beams?

Transverse horizontal forces H_T (crab surge) are distributed between the two runway beams in proportion to their lateral stiffness. For identical runway beams on both sides, each beam resists 50% of H_T. Longitudinal forces H_L (traction) are resisted by the runway beam that the driven end carriage runs on — typically one rail per runway span. EN 1993-6 Clause 2.4 requires that the runway structure is capable of resisting the full H_L on either rail. Where the runway beam provides restraint to the building column, the horizontal force also enters the bracing system.

Related Pages

• EN 1993 Fatigue → — Fatigue per EN 1993-1-9
• EN 1993 Lateral Torsional Buckling → — LTB per EN 1993-1-1
• EN 1993 Load Combinations → — ULS and SLS combinations
• EN 1993 Steel Grades → — S235 to S460 grade properties
• All European References →

Educational reference only. Design per EN 1993-6:2007, EN 1991-3:2006, and EN 1993-1-9:2005. Crane wheel loads and dynamic factors must be obtained from the crane manufacturer's data sheet. Fatigue assessment requires knowledge of the duty cycle and load spectrum. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification by a qualified structural engineer.

Design Resources

Calculator tools

• Steel Beam Calculator
• Fatigue Assessment Calculator
• Load Combination Calculator
• Welded Connection Calculator

Design guides

• Crane Runway Beam Worked Example
• Fatigue Design Guide
• Lateral Torsional Buckling Guide
• Bolted Connection Worked Example
• Steel Connection Calculator Guide

Reference pages

• EU Fatigue Assessment
• EU Lateral Torsional Buckling
• AU Fatigue Assessment

Disclaimer: This content is for educational purposes only. Results must be verified by a licensed professional engineer. Steel Calculator provides preliminary design tools — NOT a substitute for professional engineering judgment.