1. Building Bridges

2. Physics of Bridge Building
Three basic types
Span: simplest form – beam supported on vertical supports. Also truss bridge, cantilever bridge
Arch: compression forces push outwards horizontally against the supports
Suspension: main cables anchored to towers, suspender cables support roadway. Cables are in tension.

3. A bridge in New South Wales, Australia example of truss system (rigid triangular framework)

4. Forth Rail Bridge example of cantilever bridge

5. Clachan Bridge, Isle of Seil “The Bridge over the Atlantic” example of stone arch bridge

6. Pont Du Gard Roman Aqueduct triple arch bridge

7. Corrieshalloch Gorge Suspension Bridge

8. Golden Gate Bridge San Fransisco example of suspension bridge

9. Akashi Kaikyo Bridge Japan (Longest single span in the world)
3-span 2-hinged truss-stiffened suspension bridge

10. Oresund Bridge, linking Sweden and Denmark

11. Lake Pontchartrain Causeway New Orleans, LA

12. Some Physics Considerations
Choice of material
Strength:
in tension, compression, bending, torsion
Shape of framework
(why triangular?)
Testing the design – use of models
Physical scale models
Computer models

13. Tacoma Narrows Bridge

14. Tacoma Narrows Bridge

15. Tacoma Narrows Bridge

16. Tacoma Narrows Bridge

17. Millenium Bridge, River Thames, London

18. Millenium Bridge, River Thames, London

19. The Bridge Competition
You are a team of bridge designers working for the internationally known bridge building company ………………………………………….
(choose a name for your company)
Your task is to design and build a single span bridge to the specifications given on the sheet, using the materials provided.
The bridges will be judged on three categories
Technical Merit
Artistic Impression
Weight

20. Bridge specifications
Bridge has to span a gorge 90 cm wide, with sides at the same height.
The centre point of the underside of the bridge must be at least 10 cm higher than ground level.
The bridge has to carry a continuous single track car deck ( made from card provided), allowing a model car to travel safely across the gorge.
The car deck can have a maximum incline of 30 degrees at any point.
The bridge should be sufficiently rigid that the span bends less than 2 cm if CAN! stops at centre.

21. Technical specifications
Single-track car deck (made from card)
Coke can (full)
Makes bridge bend by less than 2cm at the centre
<30°
>10cm
>90cm

22. Competition Results