Bridge Builder & Truss Simulator
Build a bridge over a canyon and find out if it holds. Click to place joints and drag members between them, choose road deck or plain struts, then run the load test: a truck rolls across while the direct-stiffness solver computes the force in every member at each instant. Members glow red in tension and blue in compression, thicken with load, and fail visibly — snapping in tension or buckling in compression — with the wreck tumbling into the gorge. The cost meter totals material as you build, so the real game is the engineering one: carry the load with the cheapest structure. Presets load a Pratt, Howe and Warren truss to study and improve.
Runs 100% in your browser — simulations are computed locally on your device.
Read the full guide to this tool
Notes
- The solver assembles the classic pin-jointed truss stiffness matrix and solves for joint displacements each frame; member force = axial stiffness × elongation, positive in tension.
- Compression members fail earlier than tension members: the buckling limit follows Euler’s formula, dropping with the square of member length — long struts are weak struts.
- Triangles are the whole secret of truss design: any joint layout that leaves a quadrilateral unbraced is a mechanism that folds instead of carrying load.
- Runs 100% in your browser — simulations are computed locally on your device.
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