A rod brace's governing failure mode — yield or rupture at the threaded root — depends entirely on the code's own fu/fy ratio and partial safety factors, and IS 800's own reference grade produces the opposite result from what this series' AISC 360 companion finds for a comparable rod.
Every check above runs automatically inside the Structyze Bracing 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
- Brace type: rod, factored tension 60 kN
- Rod diameter 20 mm
- Rod material Fy = 250 MPa, Fu = 410 MPa
- End connection: bolted, 10 mm gusset (Fu = 410 MPa)
- 2 × M20, Grade 4.6 bolts, edge 35 mm, pitch 60 mm
Working Through It
The rod's gross area Ag ≈ 314.2 mm², net area at the threaded root Anet = 0.78(314.2) ≈ 245.0 mm² — the standard geometric convention.
Two failure modes compete: gross yielding Tdg = 314.2(250)/1.1/1000 ≈ 71.40 kN, versus net-section rupture Tdn = 0.9(245.0)(410)/1.25/1000 ≈ 72.34 kN. Yield governs, narrowly — only about 1.3% below rupture, a close race decided by Fe410's own fy/fu ratio combined with the two different partial safety factors (γm0 = 1.10 for yield, γm1 = 1.25 for rupture).
The end connection carries far more margin: governing per-bolt capacity 45.27 kN, group capacity 90.55 kN against the 60 kN demand — utilisation 0.663.
What Governs, and Why
The rod itself governs at utilisation 0.840, but by gross yielding (71.40 kN), not net-section rupture at the threaded root (72.34 kN) — the opposite of what this series' AISC 360 companion volume finds for its own rod-brace grade combination. Dividing both capacities through by Ag shows why: fy/γm0 = 227.3 MPa against 0.9(0.78)fu/γm1 ≈ 230.3 MPa. Within 1.3% of each other for Fe410's own grade, decided in yield's favour purely by IS 800's specific factor combination, not by any modelling choice.
Where Structyze Takes Over
Every check above runs automatically inside the Structyze Bracing 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 Bracing 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 the same physical rod yield under IS 800 but rupture under AISC 360?
It comes down to each code's own reference material grade and partial safety factors — IS 800's Fe410 (fy=250, fu=410) combined with γm0=1.10 and γm1=1.25 happens to land the two capacities within 1.3% of each other, tipped toward yield; AISC 360's ASTM grade and LRFD resistance factors, applied to a comparable rod, land the balance the other way. Neither code is wrong — it's a genuine consequence of each grade/factor combination.
What's the practical takeaway from a race this close?
When two failure modes sit within a percent or two of each other, the governing mode itself becomes fairly arbitrary to small input changes — a slightly different rod diameter, thread convention, or material grade could easily flip which one governs, so neither number should be treated as having much independent significance beyond confirming the rod passes overall.
Final Thoughts
This rod brace is a genuine illustration of how the same physical member can fail by a different mechanism under two different codes — not because one code is more conservative, but because each one's own grade and factor combination decides the race differently.