The three pictures below show three different kinds of bridges. Summarize the information by selecting and reporting the main features and make comparisons where relevant.
Model answer 1
The diagrams illustrate the design of three types of bridge.
Overall, the arch bridge is built to connect two sides of a lake, so it is the shortest in terms of both length and height. While the concrete girder bridge can cater for the longest spans (as long as there are enough piers), the suspension bridge is suitable for connecting towns, cities or islands over the ocean.
Regarding the arch bridge, its maximum length is 200m, and it can be up to 100m tall (from the bed of the lake), which only allows small ships to go through. This kind of bridge has two piers forming a semi-circular shape, with the roadway running parallel with the surface of the water.
Turning next to the concrete girder bridge, this design is suitable for bridging two banks of a certain river. Since there are piers – whose distance from one pair to the next must be under 200m – to support the pressure of vehicles and the weight of the bridge itself, its extent is unlimited. The tallest pillars are under 300m, so the girder bridge caters for medium-sized ships.
Finally, the distance between the two towers of the suspension bridge is from 400 to 2000m. It is of note that these piers are used to hang main cables with multiple suspender cables attached to the deck of the bridge to carry the weight of vehicles and the bridge. In addition, this structure is built in the sea and is tall enough to allow large vessels to pass through.