This simulator loads a five-joint Warren-style truss and solves a two-dimensional pin-jointed stiffness model in real time, letting you inspect all seven axial members, trace reactions through pin and roller bearings, and separate tension from compression as the load pattern changes.
• A real-time 3D cutaway workbench with tension/compression/near-zero color-coded chord and diagonal members, bolted gusset joint markers, pin and roller bearing assemblies, upper-joint load saddles with optional horizontal force, an undeformed reference overlay, and a member-force inspection console, with home view, focus-selected-part, toggleable full enclosure, exploded view, auto-rotate, expand and show/hide labels controls. • Adjustable support span (4-12 m), truss height (1-4 m), total downward joint load (0-200 kN), share applied at upper joint D (0-100%), horizontal load at upper joint E (-50 to +50 kN), common member area (500-5000 mm²), elastic modulus (70-210 GPa), and an inspected-member selector across all seven members (AB, BC, DE, AD, DB, BE, EC). • Loading actions: ramp loads from zero, apply full load, and release loads. • A Curves & measurements tab with member axial-force and joint vertical-displacement charts, the underlying stiffness-method equations (element stiffness, global assembly, solved displacements, member force N, stress, reactions and strain energy) and snapshot readouts (horizontal and vertical reactions, applied loads, selected member force/stress/length, maximum tension and compression, maximum joint displacement, equilibrium residual, elastic strain energy). • An Experiments tab with four guided fixtures (symmetric vertical loading, load only at joint D, increased truss depth, doubled member area) and a model verification bench that runs independent deterministic checks against a fresh model without disturbing your live trial, plus a timestamped event log and a copyable trial report. • A Learn & assess tab with guided lessons on joint equilibrium, identifying zero-force members, separating stiffness from force, and recognizing model limits, a knowledge-check quiz with reset, and a written model-scope statement with a technical reference link.
Each joint in the truss must independently balance its applied loads through the horizontal and vertical components of the connected members' axial forces. The simulator assembles a global stiffness matrix from each member's EA/L rigidity and orientation, solves for the free-joint displacements, then recovers each member's axial force N — positive for tension (shown teal), negative for compression (shown orange), and near-zero (shown gray).
In the default symmetric loading case, the two inner diagonals (DB and BE) carry zero force — a direct consequence of joint equilibrium at the unloaded center joint under symmetric upper loads. Shifting the load entirely to joint D, or adding a horizontal load, breaks that symmetry and activates those previously zero-force members.
For this statically determinate truss, changing the common member area (and therefore EA) changes the joint displacements and the elastic strain energy but leaves the axial forces themselves essentially unchanged, since the forces are set entirely by geometry and equilibrium, not by stiffness. Doubling the member area in the experiments halves the displacements while forces stay the same.
This is a small-displacement, linear-elastic, two-dimensional pin-jointed truss model in which all seven members share the selected EA and all external loads act only at the joints. It excludes member bending, compression buckling, yielding, joint eccentricity, connection design and unilateral support contact; a negative reaction is reported as an uplift demand under idealized bilateral restraints, and the geometry, gussets and section shapes shown are representative rather than a manufacturer detail.
No. Only the axial force is solved in this model — no member buckling, yielding or connection capacity check is evaluated. The color simply distinguishes the sign of the solved axial force.
Joint equilibrium can mathematically require zero axial force in a member for a particular geometry and loading — in this symmetric five-joint truss, the two inner diagonals are zero-force members under symmetric upper loads, but they become active once the load pattern changes.
No, not meaningfully — for this statically determinate truss, axial forces are set by geometry and equilibrium alone. Increasing the common member area primarily reduces joint displacements and stored strain energy, leaving forces essentially unchanged.
No. It is a small-displacement, linear-elastic, pin-jointed stiffness model that excludes member bending, buckling, yielding, joint eccentricity and connection design. A qualified structural engineer must perform any real truss design.