1. Beam Bridge

3. Sidney Lanier Bridge Under Construction

4. Beam Bridge: Forces When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

5. The continuous span... gives beam bridges the ability to span great distances. A single beam bridge rarely spans more than 250 feet. But in the Chesapeake Bay Bridge- Tunnel, several beam bridges can be linked together, creating what is called a continuous span.

6. The truss bridge...

7. Forces that act on a truss bridge

9. The arch bridge..

10. Forces that act on an arch bridge

11. How are arch bridges built? Building an arch bridge isn't easy, since the structure is completely unstable until the two spans meet in the middle. For years, engineers used a technique called centering, in which a wooden form supported both spans until they locked together at the top. A newer method supports the spans using cables anchored to the ground on either side of the bridge. This is how the New River Gorge Bridge in West Virginia was built.

14. The suspension bridge...

15. Forces that act on a suspension bridge…...

16. Cable-stayed bridges, like the Sunshine Skyway in Florida, require less cable and can be built much faster than suspension bridges. Cable- stayed bridges are becoming the most popular bridges for medium-length spans (between 500 and 3,000 feet).

19. This is what happens when you don’t pay attention in your middle school science class and you get hired to build a bridge.