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Calcs.com

Truss Analysis Wizard

Structural engineers solving 2D roof, floor, or custom truss geometries. Set nodes, member connectivity, supports, and loads in-browser - the FEA engine updates results instantly without any software to install.

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What it calculates

Solve 2D trusses with a live FEA engine. Set nodes, fixities, and members in-browser, and get shear, moment, and deflection results as you work. Covers roof, floor, and custom truss geometries with nothing to install.

How it calculates

The Truss Analysis Wizard uses a direct stiffness finite element analysis (FEA) engine to solve any planar 2D truss. You define the geometry - node coordinates, member connectivity, support fixities, and loads - and the solver assembles and inverts the global stiffness matrix to return forces and displacements simultaneously across every member.

Geometry and member modelling

Each member is modelled as a two-node axial bar element with user-specified cross-section area (A) and elastic modulus (E). The calculator supports a library of preset truss configurations - Flat Warren, Flat Pratt, Flat Howe, Flat Brown, King Post, Queen Post, Single Fan, Simple Fink, and Fink roof trusses - as well as fully custom node and element definitions. For non-custom configurations, straight chord regions are treated as continuous members rather than pin-jointed segments; this is more accurate but means results may differ slightly from a traditional hand analysis.

Stiffness assembly and solution

The solver assembles the global stiffness matrix from the individual element stiffness contributions, applies boundary conditions at pinned and roller supports, and solves the resulting system of linear equations for nodal displacements. Member end forces are back-calculated from the displacements using the element stiffness relation.

Sign conventions and outputs

  • Positive bending moment indicates that the bottom or right side of the member is in tension.
  • Positive axial load indicates a compressive load (compression-positive convention).

Results reported for each member and element include:

  • Axial force - tension or compression demand in each member
  • Shear force and bending moment envelopes along each element
  • Nodal displacements and support reactions

Output tables include overall results by member type, maximum displacements by member, support reactions, results by element number, and results by node number.

Load application

Distributed loads can be applied to chord members. For preset configurations, loads are specified over the chord length; the FEA engine converts these to equivalent nodal contributions automatically. Advanced users can also apply loads directly by element number for non-standard cases. Multiple load cases are evaluated and an envelope of governing demands is reported.

Linking to design calculators

The Truss Analysis Wizard is an analysis-only calculator. After solving, member force demands (moment, shear, axial) can be linked directly to Design Only calculators - such as timber, steel, or cold-formed steel beam calculators - so each member is checked against the relevant code without re-entering geometry or loads.

Related calculators

Portal Frame Analysis Wizard→Wood Member (Design Only - ASD)→Timber Member (Design Only)→

Support articles

How to Use the Truss Analysis Wizard→How to Create and Use a Custom Section in the Custom Truss Analysis→
Browse all docs →

What engineers say

I like using different software packages, but the reason why I use Calcs.com more often now is load linking.

Richard Faulkner

Senior Structural Engineer, Kusch Consulting Engineers

Lawrence Bowen company logo
Calcs.com is very straightforward and allows me to either analyze a section of the building or the whole thing quickly.

Lawrence Bowen

Founding Principal, CPBD, VQ Design

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Frequently asked questions

What analysis method does this calculator use?
The Truss Analysis Wizard uses a direct stiffness finite element analysis (FEA) engine. Each truss member is modelled as a two-force axial element. The solver assembles the global stiffness matrix, applies boundary conditions at pinned and roller supports, and solves for nodal displacements and member forces simultaneously.
What are the key inputs?
Key inputs are node coordinates (x, y), member connectivity (start node, end node), support fixity at each node (pinned, roller, or free), member cross-section area and elastic modulus, and applied nodal loads (force magnitude and direction). You can define any planar truss geometry - roof, floor, Pratt, Howe, or fully custom layouts.
What does the calculator output?
Outputs include axial force in every member (tension or compression), nodal displacements, and support reactions. Force diagrams and displacement plots update live as you edit geometry or loads. Results are printable in a structured report for submission or record-keeping.
Can I model multi-bay or non-standard truss geometries?
Yes. The calculator is geometry-agnostic - nodes can be placed anywhere in the plane, and members can connect any two nodes. This allows Pratt, Howe, Fink, Gambrel, arch, and multi-bay configurations. There is no limit on the number of nodes or members within the platform.
How do I handle distributed loads on top-chord members?
Distributed loads on chord members must be converted to equivalent nodal loads at the panel points before entry. Divide the distributed load by the panel spacing to get point loads at each intermediate node. For roof trusses under uniform snow or dead load, this means applying equal vertical forces at each top-chord node based on tributary length.

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