Location 1: Multi-land bridge for commuters and tourists (span 2,000 feet) Q7. ____________________have short spans usually less than 250 feet. Q2. ____________________ typically have rather short spans between 200 and 800 feet. Muddy riverbanks probably couldn’t support this type of bridge. Q6. ____________________ use as little steel as possible. The roadway hands from cables, forming a unique “A” shape. This type of bridge is made mostly of concrete, and there is room for ships to pass beneath. Location 2: Footbridge across a stream (span 100 feet) Q3. ____________________are expensive to build, and are suitable over a large body of water. Q1. ____________________ are the cheapest and easiest bridges to build. Steel is more expensive than concrete. Strengthen a bridge by setting the piers deeper into the ground. Location 4: Railroad bridge in a national park that connects two rocky bluffs (span 500 feet) Q7. ____________________ tend to sag when the span is more than 500 feet. Q4. ____________________ do not need towers or piers. The abutments push back on the curve and prevent the ends of the curve from spreading apart. Wood is strong in compression, but rots quickly in wet and rainy conditions, and it burns easily. Cast iron is strong in compression, but brittle. It breaks easily and without warning. Steel is strong in compression. It can also be arranged in a lightweight truss pattern. Places for Bridges http://www.pbs.org/wgbh/buildingbig/bridge/challenge/index.html Location 3: Highway bridge across a busy shipping port (span 5,000 feet) Q5. ____________________ would be ideal across this long span (between 2,000 and 7,000 feet). To minimize movement in the wind, stiffen the deck with an open truss structure that the wind can blow right through.

Q11. On the ____________________, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. The live load (traffic) pushes down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers. The two towers support most of the bridge’s weight. Q9. On the ____________________the arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end. The supports, called abutments, push back on the curve and prevent the ends of the curve from spreading apart. Q8. Oh the ____________________the top edge is under compression, while the bottom edge is under tension. Forces on Bridges http://www.pbs.org/wgbh/buildingbig/bridge/basics.html#beam In these force diagrams, red arrows indicate compression (pushing together), while blue arrows indicate tension (pulling apart). Q10. On the ____________________steel cables support the roadway directly by running from the roadway up to a tower, forming a unique “A” shape. Q6. This type of bridge is the most popular choice for medium-length spans (500-3,000 feet). On the ____________________, every bar experiences either a pushing (compression) or pulling (tension) force.