Polina2100Kaddik

24.06.2021 18:29 •  Английский язык

ответить на эти вопросы основываясь на содержание текста: 1. were the first bridges made of steel? 2. did people construct wooden beam type bridges in middle ages? 3. was there a great demand for railway bridges in the 19th century? 4. are people experimenting with different unusual materials for constructing bridges? 5. do paper-makers consider paper to be a strong material? 6. was a paper bridge built across the river? 7. is paper a widely used material for the bridge construction? 8. did it take engineers only 2 years to construct the bridge made of paper? 9. did engineers choose a train for testing the paper bridge? 10. can a paper bridge be laid into place by helicopter? текст: experimental bridge a bridge is a structure built to cross some natural or artificial obstacles such as river, street, railway and so on. first bridges had to be built out of the material close at hand*. in tropical jungles, suspension bridges were made of long bamboo poles. in the places where there were many forests, it was wood. simple suspension bridges were made by means of ropes and are still used in some countries. two parallel ropes were suspended from rocks or trees on each bank of the river with a platform of woven mats laid across them. when the spaniards reached south america, they found that the incas** of peru used suspension bridges made of 6 strong cables, four of which supported a platform and two cables served as handrails***. in middle ages, people constructed wooden beam type bridges. they were usually built on stone piers or wooden piles. bridges of this type are still used in japan and india. with the beginning of railway construction in the 19th century, there was a great demand for bridges and the railway companies had capital for building them. the first railway bridges were built of stone or brick. later there appeared concrete and metal bridges. the first iron bridge crossed the river severn in great britain. nowadays some people are experimenting with different unusual materials. one of them is paper. nobody considers paper to be a very strong material. however, paper-makers have another opinion. in order to prove it they built a paper bridge across a narrow canyon in nevada. the bridge had a span of 32 ft. the designers calculated that it could safety span 80 ft. it took engineers only two months to design the bridge, to test and construct it. for testing, the engineers chose a truck, which weighed 12,000 lb. this truck drove quite safely across the paper bridge. the engineers are sure that the bridge can take six times the truckload of 12,000 lb. the bridge itself weighed 9,000 lb. therefore, the structure was light enough to be laid into place by helicopter.