Load Combination Contribution Analyzer – MIDAS Support

Intro

A combination result tells you the answer but not where it came from. When a girder moment is governed by a combination of eight load cases, the question that matters in a calc package is which case produced which portion of it — whether the design is being driven by the traffic envelope or by the temperature term, and by how much.

Answering that by hand means re-running every constituent case, tabulating it, applying the factors and trusting that the arithmetic closes. The Load Combination Contribution Analyzer does it directly: it reads the combination out of the model, resolves it down through any nested sub-combinations, and reports the signed contribution of every constituent load case at every output location — then reproduces the combination from those contributions and compares it against what CIVIL NX itself reports before showing anything at all.

Developed with

MIDAS CIVIL NX 2026 (v1.0.0)

Benefits of this plugin

Every result location, not a sample — the decomposition is carried out at each element, part and component, across beam, truss, plate, plane stress, plane strain, axisymmetric, solid and link results, in local and global axes wherever MIDAS provides both.
Checked against CIVIL NX every time — each decomposition is recomposed and compared with the value the model reports for the same combination at the same location, pulled in the same request batch. A mismatch beyond tolerance stops the run, and there is no switch to turn it off.
Full precision rather than display precision — results are requested at nine significant figures instead of the model's display format, which would give two decimal places for forces. On a real eight-child combination that drops the recomposition error from 5e-3 to 1.4e-7, which is what makes the self-check meaningful.
Nested combinations resolved properly — a load case reachable down several branches is given an effective factor equal to the sum of the path products, not a single lookup, so a case that appears both directly and inside a sub-combination is reported once and correctly.
Envelopes treated as selections, not shares — the governing case is resolved for every element, part, component and sense and reported per result item rather than averaged or flattened, because along a member it genuinely changes.
Selection the way MIDAS does it — pick elements by structure group, boundary group, section, thickness, material or element type, each shown with its element count. Ticks are remembered per basis and combined, and typed element numbers are unioned on top.
It refuses rather than guesses — nonlinear and pushover cases, creep and shrinkage, tendon primary and secondary effects, time-history results and derived quantities such as von Mises and principal stresses are all declined with the reason given, because none of them is linear in the load cases and a number produced for them would be wrong.
Built to be read — a light and a dark theme, a proper type scale, numbers set so digits line up down a column, and CSV export of the contributions and the governing map for the calc package.

How to use this plugin?

Open your analysed model in CIVIL NX and start the plugin — the connection details are supplied automatically, and the combinations, elements, selection sets and construction stages all begin loading the moment the MAPI key verifies, so there is nothing to click first.
Choose the combination under Combination — every LCOM table is read, so anything defined in the model appears. The Combination tree underneath shows how it resolves, including whether it is envelope-valued and therefore reported as a max/min pair.
Choose the result table — beam, truss, plate, plane stress, plane strain, axisymmetric, solid or link, in force or stress and in local or global axes. The choice sets both the element type and the components on offer, and filters the element selection to that type.
Select the elements under Select elements by — switch the basis between structure group, boundary group, section, thickness, material and element type, and tick the sets you want. Set members of a type the chosen table cannot report on are skipped and counted rather than silently dropped.
Type individual element numbers into Elements if you want them, using ranges such as 700-760, 1200, 1310-1315. They are added to whatever the ticked sets already cover.
Tick the components to decompose — the list follows the chosen result table, and a sensible default is already selected.
Fill Stage:step only for construction-stage results, using the form CS3:002(last). Leave it blank for post-stage results; a stage mismatch is refused rather than assumed.
Select Run decomposition. Every constituent case is batched across the element set into as few requests as possible, and the self-check runs before any result is displayed.
Read the Results tab — pick a location with the cascading Element, Part, Component and Sense filters, which follow what the run actually produced. Each case is listed with its factor, its raw result, its signed contribution, its share of the gross and its share of the net, alongside the net, the gross, the cancellation ratio and the value CIVIL NX reports for comparison.

Use the Charts tab to see the same thing as a signed bar chart on a shared zero axis, or as a pie of the share of gross. Where contributions largely cancel, the pie is labelled as relative influence rather than proportions of the net.

Open the Governing map for an envelope combination — it lists the governing case for every element, part, component and sense, which is the part that cannot be summarised into a single answer.
Export CSV from the Results or Governing map tab for the calc package. The export carries the units, the precision returned by the API and the combination tree alongside the numbers, so the table can be read on its own.

Conclusion

The Load Combination Contribution Analyzer answers the question a combination result cannot: which load case is actually driving the design, and by how much. It removes the manual re-runs and hand tabulation, resolves nested combinations and envelopes the way CIVIL NX does rather than approximating them, and refuses the cases where a contribution would be meaningless instead of printing one anyway.

Every number it reports has been reproduced from its own constituents and checked against the model before it appears — which is what makes the output fit to put in a calc package.