Structure Collapse - Bridge Building Simulator
Structure Collapse is an interactive structural engineering simulator where you build bridges, towers, and custom structures from rigid beams and joints, then test them against realistic physics forces. Place joints, connect them with beams, anchor them to the ground, and activate physics to watch gravity, weight, wind, and wrecking balls stress-test your design. Beams change color based on stress level cyan for stable, yellow for moderate stress, red for critical before snapping catastrophically. Perfect for aspiring engineers learning structural mechanics, educators demonstrating load distribution, or anyone who finds structural failures oddly satisfying. Includes bridge and tower templates to get started instantly. Runs entirely client-side with no downloads or signups required.
Structure Stats
How to Use This Simulator
- Step 1 - Select build mode: Joint (place movable connection points), Anchor (place fixed points anchored to ground), Beam (connect two joints with rigid beams), or Delete (remove elements).
- Step 2 - Click to place joints/anchors. In Beam mode, click one joint, then another to connect them. Build arches, trusses, or towers use templates for inspiration.
- Step 3 - Adjust gravity (0-2x) and optionally enable wind for dynamic horizontal forces. Click Start Physics to activate the simulation.
- Step 4 - Add stress tests: Weight drops a static mass, Wrecking Ball launches a heavy projectile. Watch stress levels (yellow/red beams) and count failures as beams snap under load.
Why This Structural Physics?
Structure Collapse uses a constraint-based physics engine where beams act as distance constraints between joints. Each frame, the engine iterates multiple times (3 passes) to enforce that beam lengths match their rest length, using Verlet integration for position updates. When external forces (gravity, weights, collisions) pull joints apart, beams resist by applying corrective forces proportional to the strain (difference between current and rest length).
Beams break when stress exceeds 50% of their rest length, simulating material failure under excessive tension or compression. This approach, inspired by games like Poly Bridge and Bridge Constructor, balances real-world structural concepts (load distribution, triangulation strength, cantilever weakness) with performance the engine runs at 60 FPS even with 100+ beams. Anchor points simulate fixed supports, creating realistic failure modes where unsupported spans collapse while anchored sections hold.
Pro tip: Triangles are the strongest structural shape use diagonal bracing to distribute loads evenly. Avoid long unsupported horizontal beams (they'll sag and snap). For towers, taper upward (wider base, narrower top) to prevent top-heavy collapse. Enable wind to test lateral stability good designs resist horizontal forces without toppling. The stress color system (cyan→yellow→red) teaches you to identify weak points before catastrophic failure, mimicking real engineering analysis tools.