1. A brief study of bridges
Owachomo Bridge, Natural Bridges National Monument, San Juan County, Utah; near Blanding, Utah.

2. How to talk about bridges:
Span- the distance between supports
Supports- piers, columns, or towers that elevate the bridge.
Deck- The section that we walk or drive on
Members- supporting pieces within a bridge.

3. Forces in Bridges

4. is a force that acts to compress or shorten. (a push)
Compression
is a force that acts to compress or shorten. (a push)

5. is a force that acts to expand or lengthen. (a pull)
Tension
is a force that acts to expand or lengthen. (a pull)

6. Bending
An action that creates both compression and tension in object being bent. T C

7. What happen when the forces are too much?
Snapping- too much tension/ pulls apart.
Buckling- too much compression, deflects to the side.

8. Dissipation All bridges are subject to forces.
The goal of designing a bridge is to dissipate the forces, that is to spread them out over a greater area.

9. Beam Bridge Notes: - Top in compression, bottom in tension
- Max span ~ 200 feet

10. A thicker beam bridge
Still experiences compression and tension but the forces are dissipated.
But a thick beam bridge is pretty heavy…

11. TRUSS BRIDGE Notes: - A thicker beam bridge
- C and T forces are more spread out
- Max span ~400 feet

12. ARCH BRIDGE Notes: - All parts are in compression - Max span ~ 1000 ft
- VERY sturdy but labor intensive.
Roman arches are >2000 years old

13. SUSPENSION BRIDGE Instead of supporting the deck from below,
Suspension bridges hang the deck from a
cable above.
But the towers need balanced forces.

14. SUSPENSION BRIDGE Notes: - Supports (towers) in compression,
- cables in tension
- Max span ~ 7000 feet

15. CABLE STAY BRIDGE Notes: - Stiffer than a suspension bridge because
all points of deck connect to a support.
- Much cheaper to build than a suspension
- Max span ~ 5000 feet

16. Truss Bridge Geometry
What shape do you see a lot of?

17. Truss Bridge Geometry
Squares can collapse by rotating at the joints without ever breaking the members.
Triangles can only collapse if a member breaks.