A steel pipe-rack trestle is a simple portal frame — a cap beam carrying pipe load, columns carrying axial reaction plus a lateral cantilever moment from pipe friction — and it's easy to underestimate just how much that lateral moment, not the axial load, ends up driving the column design.
Every check above runs automatically inside the Structyze Pipe Support 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
- Cap beam span 4 m, column height 3 m, 2 columns per bay
- Cap beam 250 × 150 × 12 × 8 mm
- Column 200 × 200 × 10 × 7 mm
- Pipe load 6 kN/m, longitudinal friction force 12 kN
- Material ASTM A992/A572 Grade 50, Fy = 345 MPa
Working Through It
The cap beam itself is an ordinary simply-supported flexural check — factored load 10.10 kN/m gives Mu = 20.20 kN·m against a plastic capacity of 164.7 kN·m (utilisation 0.123), with shear running even lighter at 0.049.
Each column's axial load is just half the beam's total reaction plus its own self-weight: 21.66 kN — tiny against its buckling capacity (utilisation 0.017). But the longitudinal friction force, applied as a simple cantilever moment at the column base over the full 3 m height and shared between the 2 columns, gives Mu = 1.6(12)(3)/2 = 28.8 kN·m — a significant moment from a fairly modest 12 kN force, purely because it acts over the full unbraced column height.
The combined interaction check, Pu/φcPn + (8/9)(Mu/Mc), comes to 0.017 + 0.209 = 0.226 — almost entirely from the moment term.
What Governs, and Why
The column combined-interaction check governs the whole frame at utilisation 0.226, driven almost entirely by the lateral cantilever moment (0.209 of that total) rather than the axial term (0.017). A modest 12 kN longitudinal force, acting at the full column height as an unbraced cantilever, matters far more to this design than the much larger vertical pipe load does.
Where Structyze Takes Over
Every check above runs automatically inside the Structyze Pipe Support 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 Pipe Support 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 does a small longitudinal force matter so much?
Because it's applied as a cantilever moment over the full unbraced column height — moment scales closely with lever arm, so even a modest force at a 3 m height produces a meaningfully larger moment than the same force would at a shorter height or with some bracing continuity.
What isn't modelled in this simplified method?
Bracing and portal-frame continuity between the beam and columns, which would reduce the effective column moment, aren't included here — nor is the possibility of multiple discrete pipe reactions along the beam rather than a single uniform load.
Final Thoughts
A pipe rack's lateral friction-force moment is the kind of secondary effect that's easy to under-weight by hand when the vertical pipe load looks like the 'real' design load.