BS EN 1993's combined shear-and-tension bolt check is genuinely linear, not quadratic — a real structural difference from IS 800 and CSA S16's elliptical interaction, and the 1.4 divisor on the tension term is a deliberate relief factor, not an error, reflecting that shear and tension don't interact as severely for a bearing-type bolt as the quadratic form implies.
Every check above runs automatically inside the Structyze Moment End-Plate Connection module — this particular module is part of the full desktop catalogue rather than the free browser trial, since the trial only carries a curated flagship set. You can still try the free trial modules right now to see the same calculation style in action on RCC Beam, Column, Slab and a handful of others.
The Example We'll Use
- Member 400 × 200 × 12 × 8 mm, fy = 235 MPa
- Design moment 120 kN·m, shear 80 kN
- End plate 32 mm, fy = 235 MPa
- 4 × M24 Grade 8.8 bolts (tension zone), pitch 90 mm
- Lever arm 360 mm, cantilever projection 50 mm
Working Through It
Bolt tension from the couple: T = 333.3 kN total, Tbolt = 83.33 kN; Vbolt = 20 kN. Bolt capacities: Ft,Rd ≈ 203.3 kN, Fv,Rd ≈ 135.5 kN.
The linear interaction: Fv,Ed/Fv,Rd + Ft,Ed/(1.4Ft,Rd) = 20/135.5 + 83.33/(1.4×203.3) = 0.148 + 0.293 = 0.441. A bolt fully utilized in tension alone (Ft,Ed = Ft,Rd) would still have 1/1.4 ≈ 0.71 of headroom before this check fails — genuine relief the quadratic form doesn't offer.
End plate bending, at utilisation 0.877, is the tightest check — the plate itself, spanning as a cantilever from the bolt line to the tension flange, limits this connection even with a genuinely high-grade 8.8 bolt in the tension zone.
What Governs, and Why
End-plate bending governs at utilisation 0.877, well ahead of every bolt and weld check. The actually linear bolt interaction, with its 1.4 relief factor on the tension term, is architecturally distinct from the quadratic ellipse IS 800, CSA S16 and NZS 3404 all share — worth recognising as a real difference in how EC3 combines these two demands, not just a notational variant.
Where Structyze Takes Over
Every check above runs automatically inside the Structyze Moment End-Plate Connection module — this particular module is part of the full desktop catalogue rather than the free browser trial, since the trial only carries a curated flagship set. You can still try the free trial modules right now to see the same calculation style in action on RCC Beam, Column, Slab and a handful of others.
For Moment End-Plate Connection and the rest of the full catalogue — 80+ components across RCC, Steel, Composite, Timber, Masonry and more, across 20+ design codes — buy the full Structyze desktop app or see everything it does on the Software page.
Quick FAQ
Why would EC3 give a bolt more relief on combined loading than the quadratic codes?
The 1.4 divisor reflects EC3's own calibration of how a bearing-type bolt actually behaves under combined shear and tension — test data underlying Table 3.4 apparently showed less severe interaction between the two demands than a simple quadratic ellipse would predict, so the code builds that empirical relief directly into the tension term rather than using the more conservative elliptical form.
Is this linear form always more generous than the quadratic form?
Not necessarily at every combination of ratios — but for a bolt with a genuinely dominant tension demand and comparatively small shear (as here), the 1.4 relief factor on tension combined with a simple linear sum tends to leave real headroom that a quadratic check's squared terms wouldn't erase as quickly.
Final Thoughts
The linear-versus-quadratic split in how different codes combine bolt shear and tension is one of the more genuinely consequential structural differences in this whole connections series — worth checking explicitly which form applies before assuming they're interchangeable.