Free Tool · EN 1993-1-5 · Plate Girders · Steel

Plate Girder Design

Class 3 / Class 4 plate girder design per <strong>EN 1993-1-5</strong>. Input flange and web dimensions, steel grade, design moments and shears — get M<sub>c,Rd</sub>, V<sub>bw,Rd</sub>, Class 4 effective section, and deflection check.

EN DE FR ES IT NL PL SV DA
Section Geometry
Welded I-section plate girder assumed. Rolled sections treated with welded limits (conservative).
Design Actions
Span for deflection check (L/250 limit).
Design bending moment at midspan or support. Leave 0 to skip. · Design shear force. Leave 0 to skip.
Uniformly distributed load for deflection. Leave 0 to skip.
γM1 = 1.0 per EN 1993-1-5 §6.1(1).
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Related tools
Lateral-Torsional Buckling (§6.3.2) Bolted Splice (§3.6) Column Buckling (§6.3.1) Welded Moment Connection (§4.5.3.2)
Design Results
—
— Section class
— M_c,Rd (kNm)
— V_bw,Rd (kN)
Steel grade —
fy — MPa
bf/tf —
hw/tw —
ε = √(235/fy) —
Plate Girder — Cross Section
hw=750mm bf=200mm tw=8 G k_σ σ₁ σ₂
Utilization Checks
<80% 80–100% >100%
Clause Checks
Clause Check η Status
Governing check: —

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Frequently Asked Questions
What makes a plate girder different from a hot-rolled beam?
A plate girder is a built-up I-section where the flanges and web are fabricated from plates (welded or bolted). Hot-rolled beams (IPE, HEB) are produced by rolling. Plate girders allow arbitrary dimensions — deeper webs, wider/thicker flanges — giving much higher moment and shear capacity for the same weight. The downside is you must check Class 3/Class 4 slenderness per EN 1993-1-5 §5 because the as-built dimensions are less uniform than rolled sections.
When does a plate girder fall into Class 4?
Class 4 applies when any part of the cross-section exceeds the slenderness limits in EN 1993-1-5 Table 5.2. For an internal web, Class 3 requires hw/tw ≤ 38ε (rolled) or 33ε (welded). Class 4 applies when 33ε < hw/tw ≤ 42ε for a welded S355 girder (ε = 0.814, so 33ε = 26.9). In practice, most plate girders with hw/tw > 30 are Class 4 — you must use effective widths (Annex E of EN 1993-1-5) when calculating stiffness and resistance.
How is the effective section calculated for Class 4?
EN 1993-1-5 §5.5.2 gives the effective width b_eff = ρ·b where ρ = (0.772 + 0.124/λ̄_p²) ≤ 1.0. The slenderness λ̄_p = √(fy/σ_cr) where σ_cr = k_σ·π²·E/(12(1−ν²))·(t/b)². For webs under a stress gradient (compression at one edge, tension at the other), k_σ = 5.98 − 1.31ψ + 0.396ψ² where ψ is the edge stress ratio. The web compressed portion is reduced, reducing the effective stiffness and moment capacity.
How is V_bw,Rd computed?
EN 1993-1-5 §5.4.6 models the post-buckling tension field. The non-dimensional web slenderness λ̄_w = (hw/tw)/(37.4·ε·√(kτ)). If λ̄_w ≤ 0.83/η (η = 1.20), the web carries the full shear yield. If λ̄_w > 0.83/η, tension field develops and χ_w = 1.37/(0.7 + λ̄_w). V_bw,Rd = χ_w·fy·hw·tw/(√3·γM1). Rigid end posts (stiffeners at supports) give χ_w = 1.37/(0.7 + λ̄_w); flexible end posts give χ_w = 0.83/λ̄_w — less efficient but applicable when end stiffeners are absent.
What is web-flange buckling (flange-induced)?
EN 1993-1-5 §6.2.7 checks that the web does not buckle in its own plane due to compression from the flange. Annex A of EN 1993-1-5 gives the limit. For very slender plate girders where the flange is thick but the web is thin (bf/tf >> hw/tw), this check can govern. The reduction factor χ_f is applied to the flange contribution in the moment resistance calculation.
Does γM1 = 1.0 apply for plate girders?
Yes. EN 1993-1-5 §6.1(1) recommends γM1 = 1.0 for resistance of cross-sections and members. NL (NEN-EN), DE (DIN EN), BE, and FR national annexes all confirm γM1 = 1.0 for plate girder design. Some legacy designs use γM1 = 1.1 but this is not EN-compliant.