Truss Analysis Calculator
Solve a complete pin-jointed truss estimate with stability and equilibrium checks.
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- Free preview: original input geometry and result labels, with computed figures and deformed output hidden.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days or ₹79 for 1 week, a one-time payment that never renews. Unlock: Pro pass, $5.99 for 30 days or $2.99 for 1 week, a one-time payment that never renews.
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Results are estimates from the formulas shown, not a professional design or certification. Have a qualified engineer verify anything safety-critical (structures, electrical installations, gas or pressure systems).
About the Truss Analysis Calculator
Define every node, axial member, support and point load of a 2D pin-jointed truss, or start from a Pratt, Howe or Warren template. The direct stiffness method assembles each member’s EA/L stiffness and solves for the joints’ unrestrained degrees of freedom. A positive member force means tension, a negative one compression.
The free preview shows the model and the result labels with the computed figures and the deformed shape hidden; a Pro pass shows everything, with copy and CSV, SVG, text or PDF downloads. Results are linear-elastic, small-displacement estimates for learning and checking, not a professional design: a stable solution is no safety approval. Check the units, geometry, supports, member properties and every design requirement that applies.
How to use it
- Choose a template and enter its span, height, number of panels, E, area and load, then select Solve. To change single members, loads or supports, select Load the template and edit the JSON model. Units are SI: coordinates in metres, E in pascals, areas in m² and loads in newtons.
- Set fixX and fixY for a pin, or only one of them for a roller along an axis; define both ends of every member and each loaded node’s force components.
- Select Solve, and check the stability and numerical-conditioning message before you use any force.
- Review every axial force, stress, reaction and joint displacement, and set a deformation amplification for the drawing.
- With a Pro pass, download the CSV, SVG, text or paginated PDF report. There is no limit on the number of members.
Examples
Two supports 2 m apart; the apex 1 m high; 10 kN down at the apex
Vertical reactions of 5 kN each; 5 kN tension in the bottom chord; 7.071 kN compression in each diagonal
The forces follow from equilibrium at the joints; the displacements also depend on E and A.
Method and source
For each axial member, k=(EA/L) bᵀb with b=[−c,−s,c,s]. Assemble the global stiffness K, prescribe supported displacements and solve Kff uf=Ff; recover axial N=(EA/L)b u and reactions R=Ku−F. See the author’s Matrix Stiffness Method teaching notes, plane-truss chapter, and MIT’s finite-element analysis process. This implementation uses a diagonal-scaled finite-precision solver; teaching examples do not certify a physical design.
Limitations
- Only straight axial members, pin joints, linear elastic properties and small displacements are modelled. Bending, buckling, yielding, geometric non-linearity, self-weight, support settlement and design-code checks are not included.
- Rollers move along the x or y axis (fixX or fixY); inclined supports are not available.
- Scaled Cholesky pivots flag a mechanism or severe numerical conditioning; this numerical check does not prove that a real structure is stable.
- The full stiffness matrix needs enough device memory; there is no limit on the number of nodes or members.
- The PDF font covers most Latin, Greek and Cyrillic names. A name it cannot show gives a clear export error; the CSV, SVG and text files keep every name as you typed it.
Privacy
On this device: nothing is sent
The model and the calculations stay on this device. Only the report font loads from this site; nothing is uploaded and no AI is used.
Frequently asked questions
What do I get without a pass?
Without a pass, Truss Analysis Calculator shows original input geometry and result labels, with computed figures and deformed output hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How do I represent a pin or roller?
Set fixX and fixY true for a pin. A vertical reaction-only roller has fixX false and fixY true. Loads and reactions use positive global x/right and y/up.
Are compression forces safe?
A negative axial force only identifies compression in this elastic model. Buckling, strength and connection design need separate professional checks.
What does an unstable result mean?
The supported matrix could not be solved reliably at numerical precision. Inspect missing constraints, disconnected joints, mechanisms, nearly collinear geometry and large stiffness contrasts.
Are the example elastic properties verified material specifications?
No. Template defaults are editable numerical examples, not a material certificate or design recommendation.