;colony/science / Engineering & Materials
⚙ Engineering & Materials
Engineering & Materials
How the built world stays up — where the weight goes in a bridge, and what makes one material bend where another snaps.
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Try it now · Plate 67
How do bridges hold so much weight?
Drag the load along the span and switch beam / arch / truss.
PLATE 67 · WHERE THE WEIGHT GOES
Structure
Drag the weight along the deck — watch each design cope.
Load position 50% along the span
Or drag the weight directly on the deck.
Deck sag
26units
Stiffness
3/ 9
Push down in the middle of a plank and it bends — the top gets squeezed,
the bottom gets stretched. That's a beam, and it sags a lot. An arch turns the
whole load into a squeeze and pushes it sideways into the ground, so it barely moves.
A truss chops the bridge into triangles: each bar just pulls or pushes in a
straight line, and triangles can't be squashed out of shape. Drag the weight and watch
the beam sag worst in the middle.
Every question
Engineering & Materials, answered twice.
Plate 67Open → How do bridges hold so much weight? A bridge doesn’t resist weight so much as redirect it. Every shape (beam, arch, truss) is a different scheme for steering the load down into the ground. Plate 68Open → What makes a material strong? “Strong” isn’t one thing. Steel bends and recovers, glass is stiff but snaps without warning, rubber stretches forever — three different ways to be strong, or to fail. Plate 98Open → Why do steel ships float? A solid lump of steel sinks; shape that same steel into a hull around a pocket of air and it floats. Average density is what decides, and hull plus trapped air comes out lighter than water. Plate 142Open → Why don't domes fall in? A flat roof over a wide room needs columns or it sags. A dome spans the same room with nothing underneath — it turns the weight pressing down into a squeeze that runs down its own curve. Plate 143Open → Why is concrete reinforced with steel? Concrete is wonderful when you squeeze it and useless when you stretch it. A loaded beam stretches along its underside — so that is exactly where the steel goes. Plate 165Open → How does a stone arch hold up with no glue? A stone arch uses no glue at all. Every stone is squeezed against its neighbours, and the curve funnels all that weight down to the ground as pure compression — as long as the line of force stays inside the stones. Plate 169Open → How does a maglev train float? A maglev train has no wheels. Magnets lift it a few millimetres clear of the track and a travelling magnetic wave drags it forward, so nothing ever touches and there is no rolling friction to slow it down.
— ;colony