Modeling
Bars, beams, 3D frames, slabs and walls. Geometry, sections, supports and releases that behave like the real structure.
Modeling 2 min read
Elementarium models structures with structural primitives, not generic geometry. You place members and surfaces, assign sections and materials, and describe how they are held. The mesh follows from that description.
In this section
- 01Bars, beams and trussesWhen a member should be a bar and when a beam, how to model trusses and bracing, and what to do about members that only work in tension.
- 02Drawings & snappingImporting a DXF as a reference underlay, choosing its units and plane, and snapping model geometry onto it accurately.
- 03Elastic foundationsGrade beams, strip footings and walls on ground as line supports on springs — choosing a subgrade modulus, and where the model stops being true.
- 04Plane frames in a 3D solverWhen to use the 2D Frame and 2D Truss model types, why a flat structure in a 3D model is a mechanism, and how to restrain it.
- 05Sections & materialsWhat a section and a material contribute to the stiffness matrix and the design checks, and the values worth checking twice.
- 06Slabs, walls and shellsModelling surfaces in Elementarium — outlines, openings and thickness, how a beam or a wall attaches to a slab, local axes, and what a surface result means.
- 07Structure generatorsThirty-five parametric structures — trusses, frames, arches, towers, domes and shells — generated from a few dimensions, with supports and loads.
- 08Supports & releasesPins, fixities, springs and end releases — what each one does to the stiffness matrix, and when each is right.
- 09Your first modelThe modeling loop end to end — geometry, sections, supports and releases — on a structure small enough to check by hand.
The object model
| Object | What it represents | Typical use |
|---|---|---|
| Node | A point with up to six degrees of freedom | Connections, supports, load application |
| Bar | Axial-only member | Trusses, bracing, ties |
| Beam | Member with bending, shear and torsion | Frames, beams, columns |
| Plate | Surface carrying out-of-plane bending | Slabs, rafts |
| Wall | Surface carrying in-plane forces | Shear walls, cores |
| Shell | Surface carrying both | Tanks, folded plates, general surfaces |
| Support | Restraint on a node, free / rigid / spring per global direction | Foundations, bearings |
| Line support | The same, per unit length along a member or a slab edge | Grade beams, strip footings, a wall under a slab |
| Release | Local removal of continuity, full or partial | Pinned ends, semi-rigid joints |
| Rigid arm | A constraint tying an offset node to its master | Eccentric joints, offsets |
| Drawing | An imported DXF, as reference geometry only | Setting out against the architect's plan |
The modeling loop
- Bring in a reference drawing, or work from coordinates, so geometry lands on real dimensions instead of approximate clicks.
- Draw members and surfaces against it.
- Assign sections and materials, once each, reused everywhere.
- Describe the supports and any releases.
- Mesh the surfaces (Meshing).
- Load it (Loads and combinations).
- Solve and check (Analysis, Design checks).
Steps 1–4 are where models go wrong. A model that solves cleanly can still be the wrong model, and no mesh refinement fixes a support that should have been a spring.
Modeling principles worth keeping
- Prefer the simplest element that carries the action. A truss chord that genuinely cannot take moment should be a bar, not a beam released at both ends: the bar says what you mean, and has no torsion to leave free.
- Be deliberate about fixity. Full fixity is rare in real construction. If a base is neither pinned nor fixed, model it as a rotational spring and state the stiffness you assumed.
- Keep the model auditable. Name members, group them by function and use consistent section names. Six months later, the reviewer is you.
Something wrong or unclear on this page? Tell us, and it gets corrected.