Eurocode Moving Load Case Generator – MIDAS Support

Intro

EN 1991-2 traffic loading is a long typing job before it is an engineering one. Load Model 1 alone is a tandem system and a UDL whose values change with the notional lane, each scaled by its own adjustment factor; Load Model 2 is a separate single axle; Load Model 3 is a set of special vehicles of which only one may be on the bridge at a time; and none of that touches the fatigue models of clause 4.6 or the rail models of Section 6. Every one of them has to be created as a vehicle in MIDAS and then given a moving load case with the right lanes, the right notional lane numbering and the right factors, and the whole set has to be built again the moment a lane changes. The Eurocode Moving Load Generator does that work: it reads the traffic lanes from the open model, takes the traffic load groups of Table 4.4a as the starting point, and writes the vehicles and the moving load cases that follow from them.

Developed with

MIDAS CIVIL NX 2026 (v2.2) — plugin version 1.0.0

Benefits of this plugin

The traffic load groups come first — EN 1991-2 Table 4.4a is how the code wants traffic actions taken, so gr1a, gr1b, gr3, gr4 and gr5 are the primary selection rather than an afterthought. Each is one variable action for combination, they are mutually exclusive by clause 4.5.1, and picking one ticks the load models it carries so the two can never fall out of step.
The whole of EN 1991-2 in one place — Load Models 1 to 4 and footway loading from Section 4, fatigue load models FLM1 to FLM4 from clause 4.6, and LM71, SW/0, SW/2, HSLM-A and HSLM-B from Section 6. Each is written as the matching MIDAS vehicle type, and road, fatigue and rail models can be generated in one run or separately.
The National Annex handled for what it actually is — MIDAS CIVIL NX carries a single EUROCODE entry in its moving load code list, not a National Annex list, and the only annex branch inside the program is the LM3 special vehicle set: the UK NA SV and SOV vehicles, or the EN Annex A models. The adjustment factors are plain numbers, so any annex can be expressed by editing them, and presets are supplied for the common ones.
Characteristic and frequent values, both if you want them — the psi factors of EN 1990 Table A2.1 are written to the vehicle, and each case is generated with those factors applied, ignored, or one case of each. The representative value is written into the load case name, so the MIDAS load case list says which is which without opening anything.
Notional lanes numbered once, not per case — each traffic lane in the model is given a role, and carriageway lanes take the notional lane numbering of clause 4.2.3. That numbering is what decides which row of Table 4.2 and which adjustment factor a lane receives, and the Lanes tab shows the resulting values per lane before anything is written.
Rail traffic kept on its own tracks — under Eurocode, MIDAS defines a rail lane and a road lane with the same dialog and holds both in one list, so nothing in the model says which is which. A Track role does, and it is what keeps a train off the road lanes on a combined deck. A rail case with no lane selected is written without complaint and loads nothing, so the plugin refuses to generate one.
Rail combination data written with the case — the psi1 factors by number of loaded tracks and the multiple presence factors of clause 6.8.1 Table 6.11 are written into MIDAS's Railway Bridge Data. psi0 is not asked for, because MIDAS fixes it at 0.8 when it generates load combinations.
Only the factors that actually apply — the Factors tab shows the adjustment factors with LM1, betaQ with LM2, the special vehicle set with LM3, the amplification factor with the fatigue models and the classification factor with rail. A factor belonging to a load model that is not selected is not on screen to be set in vain.
One special vehicle at a time, as the code requires — clause 4.3.4(2) assumes a single special vehicle on the bridge, so each LM3 vehicle selected gets its own case rather than all of them being loaded together. Under gr5 each is paired with LM1 on the rest of the carriageway.
Written by copying an entry of the same kind — a new vehicle is cloned from one of the same MIDAS type and a new case from one of the same family, so the exact field nesting and enum spellings MIDAS uses are preserved. Where the model holds nothing of that kind, a built-in payload is used instead, transcribed field for field from a real Eurocode model.
The moving load code is checked before anything else — the Eurocode tables only exist when the model's moving load code is set to Eurocode. The Model tab reports the code it found and refuses to write under any other, instead of failing later with an error that does not explain itself.
Nothing is silently skipped — fatigue load model 5 is built from recorded traffic data and has no standard axle set, so it cannot be generated. gr2 is not generated either: what makes it gr2 is the braking, acceleration and centrifugal forces of clause 4.4, which are static loads in MIDAS and not moving loads. Both are said plainly rather than quietly omitted.
Checked before it is written — the preview lists every vehicle and every load case with its lanes, models and status, alongside the EN 1991-2 clauses that govern them, and a dry run builds the exact payload that would be sent without touching the model. Nothing reaches the model until Generate is pressed.

How to use this plugin?

Open the bridge model in CIVIL NX and start the plugin — the connection details are supplied automatically; the Validation Check card reports the base URI and the MAPI key if either is not available.
Read the model — on the Model tab press Read model. The moving load code, the traffic lanes, and the vehicles and moving load cases already in the model are reported. If the code is not Eurocode, set it in MIDAS under Load > Moving Load > Moving Load Code and read the model again.
Choose the traffic load groups — on Load models pick which parts of EN 1991-2 apply, then tick the groups your design uses. The load models each group carries are ticked underneath: a model the group cannot be built without is locked, and the rest can be dropped, so the footway load can be unticked on a deck that has none. A case per individual load model is available as well, switched off by default.

Assign the lanes — on Lanes give every traffic lane a role: carriageway, footway, the remaining carriageway area, or track for rail. Carriageway lanes take their notional lane number. Decide whether the remaining area is loaded and whether MIDAS optimises which lanes are loaded. The table underneath shows the LM1 values each lane will carry once the adjustment factors are applied.
Set the naming — the vehicle and load case name patterns take tokens for the load model, the MIDAS sub-type, the load group, the representative value and a sequence number, so the generated names read as English rather than as a packed code. How existing cases of the same name are treated is set here too.
Confirm the factors — on Factors choose the National Annex preset, then adjust the tandem and UDL adjustment factors per notional lane, the remaining-area factor, betaQ for LM2, the LM3 special vehicle set, the psi combination factors, and the rail classification factor and Railway Bridge Data. Tick the representative values to generate: the frequent value, the characteristic value, or both.

Review the Preview — every vehicle to be created is listed with its load model, sub-type and status, and every load case with its vehicles, lanes and the group it realises, alongside the EN 1991-2 notes that govern them. Anything blocking is listed separately from anything worth checking.
Generate — on the Generate tab, Dry run builds the exact payload that would be sent without writing anything; Write to model creates the vehicles and the moving load cases in the connected model. The log records every write, and flags any entry written from the built-in payload rather than copied.

Conclusion

The Eurocode Moving Load Generator removes the slow, mechanical part of an EN 1991-2 assessment: creating a vehicle for every load model and special vehicle, and building a moving load case for each of them with its lanes, its notional lane numbering, its adjustment factors and its representative value. What is left is the engineering — which traffic load groups the structure has to carry, which National Annex values apply, and what the results mean — with every generated entry listed against the clause it comes from before anything is written to the model.