Buckling

How to turn on the buckling check in Truzme and read its results.

Last updated 2026-09-24

Quickstart

1. Open a truss and calculate it as usual.
2. In the Utilisation panel, find the Max buckling chip and turn its switch on.
3. Any member close to buckling shows up there, with a percentage and a red/amber/teal bar — 100% means it would buckle under the current load.
4. Click DETAILS on the chip to see the numbers behind the check for that member, or hover the ⓘ next to a value for its formula.
5. Switch the canvas to the Buckling diagram mode to see every member's percentage at once, not just the worst one.

What it is

A long, thin member in compression can bow out sideways and give way before its material runs out of strength. That's buckling. Truzme checks it with the Euler formula for the member's critical load, Ncr — the biggest push it can take before it buckles — and compares it with the member's actual force:

u = |Nx| / Ncr

u ≥ 1 means the compression force has reached the critical load — the member could buckle.

What the formula means, a worked example, and an interactive demo comparing two columns are in the Buckling article.

Behavior notes

Opt-in, like strength. Buckling and strength are two separate checks, each with its own switch in the Utilisation panel, both off by default. Turning one on doesn't affect the other.

Two checks, one governing member. With both switches on, a Governing badge shows which check is currently closer to failing — strength and buckling can easily point at different members, since a member can be strong but slender, or thick but overstressed.

This truss shows it: its end verticals carry as much force as the middle of the top chord, but they're shorter — so they pass the buckling check and fail the strength check instead. Compare the Buckling and Strength diagrams:

Compression-only. A member in tension always shows as fine on the Buckling chip and diagram — buckling has nothing to say about it.

I_min comes from the section. For the built-in shapes (round, tube, rectangle, hollow rectangle), Truzme computes the smallest moment of inertia from the dimensions you enter in the section editor. For a custom section there are no dimensions to compute it from, so you enter I_min yourself.

K is fixed for now. Truzme doesn't yet let you set the effective length factor per member — every member is treated as pinned at both ends (K = 1), which is the conservative, typical assumption for a truss. The Buckling article shows what other end supports would change.