Free Tool · EN 1993-1-8 §6.2.5 + §6.2.8 · No Sign-up

Column Base Plate Design

Effective T-stub area c, concrete bearing fjd, combined NEd + MEd + VEd per EN 1993-1-8 §6.2.8. Anchor bolt tension (Table 3.4) + pull-out cone (EN 1992-4). Compression, large eccentricity and uplift cases all covered.

Worked Example

HEB 300 column on C30/37 pad, 4 × M24 8.8 anchor bolts, plate 500 × 500 × 30 mm S275, weld a_w = 10 mm.
N_Ed = 800 kN (compression) · M_Ed = 120 kNm · V_Ed = 60 kN.
Eccentricity e = 150 mm — L_p/6 = 83 mm < e < L_p/2 = 250 mm → partial compression case. Weld governs (η ≈ 38%). PASS.

Inputs

Column Section

Base Plate Geometry

Foundation

Anchor Bolts

Design Loads

Base Plate Results

CheckηR_dE_dUnit

Export calculation report

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Worked Example — HEB 300 / C30/37 / N=800kN / M=120kNm

PASS η = 37.6%
Partial compression (e ≤ L_p/2)

e = 150 mm  |  L_p/6 = 83 mm  |  L_p/2 = 250 mm

bearing zone (A_eff) anchor anchor HEB 300 (b=300mm) f_jd = 21.33 MPa A_eff = 104374.81 mm² c = 62.19 mm
CheckηR_dE_dUnit
Concrete bearing (§6.2.5) 35.9% 2226.66 800 kN ✓
Moment capacity (§6.2.8) 35.5% 337.93 120 kN·m ✓
Anchor bolt tension (Table 3.4) 0.0% 813.31 0 kN ✓
Anchor pull-out cone (EN 1992-4) 0.0% 1240.9 0 kN ✓
Shear transfer (friction + bolts) 4.5% 1324.42 60 kN ✓
Column-to-plate weld (§4.5.3) 37.6% 220.68 83 N/mm² ✓
f_jd21.33 MPa
c (T-stub)62.19 mm
A_eff104374.81 mm²
N_Rd2226.66 kN
M_Rd337.93 kNm
F_t,anchor,Rd813.31 kN
z_eff415.5 mm
F_t,Ed0 kN

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FAQ — EN 1993-1-8 §6 Base Plate Design

What is the T-stub effective cantilever c?

EN 1993-1-8 §6.2.5(4): c = t_p · √(f_y / (3 · f_jd · γ_M0)). It is the additional plate overhang beyond the column profile that contributes to bearing. A thicker plate gives a larger c and hence a greater effective bearing area A_eff.

How is f_jd (bearing design strength) calculated?

f_jd = β_j · k_j · f_cd per §6.2.5(7). β_j = 2/3 for grouted joints; k_j = α from EN 1992-1-1 §6.7 area ratio (√(A_c1/A_c0), capped at 3.0); f_cd = f_ck / γ_C. For a large foundation pad relative to the plate, α → 3.0, giving f_jd → 2/3 · 3.0 · f_cd = 2 · f_cd.

How are the anchor bolt failure modes treated?

Steel failure: F_t,Rd = 0.9 · f_ub · A_s / γ_M2 (Table 3.4). Pull-out cone (EN 1992-4 §7.2): N_Rd,c = k_1 · √f_ck · h_ef^1.5 / γ_M,c. The governing capacity is the lesser of the two. For sufficient embedment depth the steel mode governs; shallow anchors may be governed by concrete cone breakout.

What are the governing eccentricity cases?

e = M_Ed / N_Ed. Case "compression": e ≤ L_p/6 — full plate in compression, no anchor tension. Case "small_ecc": L_p/6 < e ≤ L_p/2 — partial compression, anchors start to be mobilised. Case "large_ecc": e > L_p/2 — anchor tension governs M_Rd. Case "tension": N_Ed ≤ 0 — pure uplift, all anchors in tension.

What is the worked example?

HEB 300 column, C30/37 concrete pad, 4 × M24 grade 8.8 anchors, plate 500 × 500 × 30 mm S275, N_Ed = 800 kN (compression), M_Ed = 120 kNm. e = 150 mm; L_p/6 = 83 mm, L_p/2 = 250 mm → partial compression (small_ecc). f_jd = 21.3 MPa, A_eff = 104 375 mm², N_Rd = 2 227 kN. Weld governs at η = 37.6% — PASS.

Does this cover shear and weld checks?

Yes. Shear transfer: V_Rd = μ · N_c + n · F_v,Rd,bolt (μ = 0.3 friction + anchor shear per §6.2.2). Weld: τ_Ed from combined N + M on fillet weld perimeter vs f_vw,d per §4.5.3. All six checks are shown in the results table.