Free Tool · EN 1993-1-8 §7 + AISC 360-22 Ch. K + GB 50017-2017 §13

HSS K & N Joint Capacity Calculator

Design resistance of welded HSS K-joints and N-joints per EN 1993-1-8:2005 §7, AISC 360-22 Chapter K, and GB 50017-2017 §13. CHS, RHS, and SHS chord sections. Failure modes: chord face plastification, chord shear failure, punching shear, brace failure, chord sidewall buckling. National annexes: UK (γM5=1.0), DE (γM5=1.1), FR (γM5=1.25), NL/ES (γM5=1.0). CIDECT Design Guide 1 & 3 referenced.

chord (d₀ / b₀ × t₀) brace 1 (d₁) brace 2 (d₁) θ θ gap g chord length ● weld point ── chord — brace (compression) — brace (tension) - - gap
Joint Parameters EN 1993-1-8
Angle between brace axis and chord axis. Range 30°–90°.
Compression is negative. Used for chord stress function kp/kn.
Results EN §7
Geometric parameters
β = d₁/d₀ (or b₁/b₀)0.6376
γ = d₀/(2t₀)10.955
τ = t₁/t₀0.63
η = h₁/b₀0.6376
Validity check
All validity conditions satisfied ✓
Failure mode resistances
[A] Chord face plastification 452.15 kN
EN 1993-1-8 Table 7.2 Eq. 7.1
N₁,Rd = kp·fy0·t₀²·(2.8+14.2β²)/(sinθ·γM5) = 1.0505·355·10²·(2.8+14.2·0.6376²)/(sin45°·1)
[C] Punching shear 2659.72 kN
EN 1993-1-8 Table 7.2 Eq. 7.3
N₁,Rd = fy0·t₀·π·d₁·(1+sinθ)/(2sin²θ·γM5)
[D] Brace failure (axial yield) 937.29 kN
EN 1993-1-8 §4.1 (brace net section)
N₁,Rd = fy1·A₁/1000
Chord gap shear (K/N)
Chord shear failure 857.14 kN
EN 1993-1-8 Table 7.4 Eq. 7.4
V_gap = 100 kN / Vpl,Rd = 857.14 kN — η = 0.1167
Governing resistance N₁,Rd
Governing resistance N₁,Rd452.15 kN
ClauseEN 1993-1-8 Table 7.2 Eq. 7.1
N_Ed350 kN
Utilisation η = N_Ed / N₁,Rd 77.41%
✓ PASS — η = 0.7741
Governing modeChord face plastification
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Frequently Asked Questions

Which joint types and codes does this calculator cover? +
K, N, T, Y and X joints. Three codes: EN 1993-1-8:2005 §7 (with UK/DE/FR/NL/ES national annexes), AISC 360-22 Chapter K (LRFD and ASD), and GB 50017-2017 §13 (with seismic γRE option). CHS, RHS and SHS chord and brace sections.
What is chord face plastification and when does it govern? +
The chord face yields plastically when the brace pushes into it. For CHS: EN Eq. 7.1, N₁,Rd = kp·fy0·t₀²·(2.8+14.2β²)/(sinθ·γM5). For RHS T/Y joints: EN Eq. 7.20. This mode usually governs for lightly loaded chords with small β ratios. The chord stress function kp/kn reduces capacity for compressive chords.
What validity ranges must be satisfied for the EN formulae? +
CHS: 0.2 ≤ β ≤ 1.0, γ ≤ 25, d₀/t₀ ≤ 50, d₁/t₁ ≤ 50, θ ≥ 30°. RHS: 0.25 ≤ β ≤ 1.0, γ ≤ 25, b₀/t₀ ≤ 35, h₀/t₀ ≤ 35, θ ≥ 30°. The calculator flags violations — outside these limits the simplified equations may be unconservative.
How does the AISC Chapter K approach differ from EN §7? +
AISC 360-22 §K3 uses similar semi-empirical formulae but with different coefficients calibrated against the CISC/AISC test database. The chord wall plastification formula uses a γ^0.2 term and Qf chord stress function. LRFD uses φ = 0.90; ASD uses Ω = 1.67. Results are typically within 10% of EN for the same geometry.
What is the GB 50017-2017 §13 seismic factor? +
GB 50017-2017 §13 allows a seismic adjustment factor γRE = 0.85 applied to joint capacity when the connection is part of a seismic load path. Enable the seismic checkbox to see the reduced capacity. The default (non-seismic) calculation uses γM = 1.1 for the material safety factor.
How does gap g affect K-joint capacity? +
For K-gap joints, the gap must satisfy g ≥ t₁ + t₀ (EN Table 7.1) to allow adequate chord shear transfer. Very small gaps reduce the chord shear capacity and can cause premature failure of the chord between the two brace welds. The chord shear check (EN Eq. 7.4) is reported separately.