1. Bridges
Mr. Ruddle

2. There are SIX main types of bridges.
Beam Bridges
Truss Bridges
Suspension Bridges
Cable Stayed Bridges
Cantilever Bridges
Arch Bridges

3. Beam Bridges
The beam bridge is the simplest form of bridge. The design dates back to ancient civilizations.
The beam bridge design consists of vertical members (piles) and horizontal members (the deck).
The piles are always under compression from the weight of the deck.
The top of the deck is under compression and the bottom is under tension. As the top is compressed the bottom must stretch to accommodate.
The force applied to the roadbed is distributed to the piles.

4. Truss Bridges Trusses are made up of a series of triangles.
The triangle is the strongest shape in the world.
The compression from the two legs of the triangle is transferred to the base.
The compression of the base pulls on the two legs. This is called tension.

5. Suspension Bridges
In a suspension bridge, the main cables are strung over the towers and anchored on each side of the gap. The road deck is then suspended from the main cable buy smaller cables.
The cables of a suspension bridge are always under tension from the weight of the roadbed.
The towers are always under compression because the cables are pulling over them.

6. Cable Stayed Bridges
Cable Stayed Bridges are considered suspension bridges.
The difference is that the cables are anchored directly to the roadbed instead of on the sides of the gap.
Compression and tension are handled same way as with the suspension bridge.
Cable Stayed bridges are more modern looking.
Notice how the cables are anchored to the roadbed instead of the land.

7. Arch Bridges ARCH TIED-ARCH
The arch diverts the weight of the roadbed to the abutments on each side.
Compression on top tightens up the arch.
The more weight you put on, the tighter the arch becomes.
Tied-Arch bridges have the arch on the top. The arch works the same way.
ARCH
TIED-ARCH

8. Cantilever Bridges
On a cantilever bridge, the main span is supported from the two ends.
There are no piles or cables supporting the main span.
Just like a diving board is supported at the end.
Notice how the main spans are supported by the structures to their left and right.

9. The End
Thank You