Theme: unusual railways 1

TEXT A. BRIDGE BUILDING I (1) Streams and rivers have always been obstacles in the way of man's travel and people had to overcome these obstacles by erecting bridges, these remarkable examples of civil engineering.	1) Daryolar va daryolar har doim insonning sayohati yo'lida to'siq bo'lib kelgan va odamlar (qurilish muhandisligining ajoyib namunalari bo'lgan ko'priklar qurish orqali bu to'siqlarni engib o'tishlari kerak edi.	(2) Nobody knows when the first bridge was built and when the idea of throwing a log over a stream came to a pre-historic man. Most probably a tree blown by the wind happened to fall across a stream and thus suggested the bridge idea accidentally. Sometimes the swift rivers washed away the soil and stone thus forming natural bridges. In tropical countries, lianas growing from one tree to another formed natural suspension bridges used by a traveller for getting across a river or a stream. One thing is quite evident today—primitive people used natural bridges thousands of years ago.	(2) Birinchi ko'prik qachon qurilganini va daryoga yog'och tashlash fikri tarixdan oldingi odamga qachon kelganini hech kim bilmaydi. Ehtimol, shamol tomonidan urilgan daraxt oqimga tushib qolgan va shuning uchun tasodifan ko'prik g'oyasini taklif qilgan. Ba'zan tez daryolar tuproq va toshlarni yuvib, tabiiy ko'priklarni hosil qilgan. Tropik mamlakatlarda bir daraxtdan ikkinchisiga o'sadigan lianalar sayohatchilar daryo yoki oqimdan o'tish uchun foydalanadigan tabiiy osma ko'priklarni hosil qilgan. Bugungi kunda bir narsa aniq - ibtidoiy odamlar ming yillar oldin tabiiy ko'priklardan foydalanganlar
(3) Very often, however, these bridges did not provide needed strength. Then people began laying several logs together, making a wider and less dangerous path. Encour­aged by this success, they tried to bridge wider streams of the banks of the stream were high, they sometimes built suspension bridges of woven lianas, the latter being fast­ened to the tree at each side of the stream.	(3) Biroq, ko'pincha bu ko'priklar kerakli kuchni ta'minlamadi. Keyin odamlar kengroq va kamroq xavfli yo'l qilib, bir nechta ignabargli yog'ochlarni birlashtira boshladilar. Ushbu muvaffaqiyatdan ruhlanib, ular daryoning baland qirg'oqlaridan kengroq oqimlarni ko'prik qilishga harakat qildilar, ular ba'zan to'qilgan lianalardan osma ko'priklarni qurdilar, ular daryoning har bir tomonida daraxtga mahkamlangan.	(4) Modern bridges are of several types. The simplest and the oldest type of bridge is the beam bridge, its pro­totype being a fallen tree or a log laid across a stream or a valley. Some of the beam bridges have a single span or beam while others have a lot of spans. The end of each span rests on concrete piers rising from the bed of the river, the end spans being laid on the river banks. Most of the larger bridges are complicated steel structures, many smaller ones being made of reinforced concrete.	(4) Zamonaviy ko'priklar bir necha turdagi. Ko'prikning eng oddiy va eng qadimgi turi bu nurli ko'prik bo'lib, uning prototipi yiqilgan daraxt yoki daryo yoki vodiy bo'ylab yotqizilgan logdir. Ba'zi nurli ko'priklar bitta oraliq yoki to'singa ega, boshqalari esa juda ko'p. Har bir oraliqning oxiri daryo tubidan ko'tarilgan beton tayanchlarga tayanadi, oxiri daryo qirg'oqlariga yotqiziladi. Kattaroq ko'priklarning aksariyati murakkab po'lat konstruktsiyalar, ko'plari esa temir-betondan qilingan
(5) The most interesting type seems to be a suspension bridge. This bridge consists of two towers built on the opposite banks of a river or a valley and used as supports for cables. A roadway, often double-deck, is suspended from the cables by means of vertical connections. II (7) The early bridges were all designed empirically, from experience gained by previous failures and successes. The pioneers who used this empirical method made some guesses as to strength required and built accordingly. Should the structure collapse^4 or shake dangerously, they ma3e the next one a little heavier .Cldt could withstand the force of the wind and carried its loads for a reasonable length of time, the builders felt safe in constructing a larger one with the same proportions. It was not until recent years that the strength of even small structures was possible to calculate.	(5) Eng qiziqarli turi osma ko'prik kabi ko'rinadi. Bu ko'prik daryo yoki vodiyning qarama-qarshi qirg'og'ida qurilgan va kabellar uchun tayanch sifatida ishlatiladigan ikkita minoradan iborat. Yo'l yo'li, ko'pincha ikki qavatli, vertikal ulanishlar yordamida kabellardan osilgan II (7) Ilk ko'priklar oldingi muvaffaqiyatsizliklar va muvaffaqiyatlar natijasida olingan tajriba asosida empirik tarzda ishlab chiqilgan. Ushbu empirik usuldan foydalangan kashshoflar talab qilinadigan kuch haqida ba'zi taxminlar qildilar va shunga mos ravishda qurdilar. Agar struktura qulab tushsa yoki xavfli silkinsa, ular keyingisini biroz og'irroq qiladi. So'nggi yillargacha hatto kichik tuzilmalarning mustahkamligini hisoblash mumkin bo'lmagan. for The histami af hridan nanntwer Imom mancr wamalas wihan	(6) The first modern suspension bridge to carry railway tracks was designed and built by John Roebling, who later gained world-wide fame as the builder of New York's Brooklyn Bridge. In 1855, a most complicated task faced the builders of bridges. They were to span the 1,000-foot (300 m) wide Niagara river. The rapid waters prevented from building piers. Most men, including experienced builders, refused the job. Then a brilliant idea came to J. Roebling—why not to build a suspension bridge? Although engineers had known the principle of suspending a bridge long before,they did not believe such a bridge to be stable enough to carry trains. It was J. Roebling who was the first to prove the possibility of using suspension bridges for railway traffic Mftjie idea to apply a suspension bridge had not come to the famous builder, the rapid waters of the Niagara river and many other swift rivers would not have been bridged.	(6) Temir yo'llarni olib o'tish uchun birinchi zamonaviy osma ko'prik Jon Roebling tomonidan loyihalashtirilgan va qurilgan bo'lib, keyinchalik u Nyu-Yorkdagi Bruklin ko'prigi quruvchisi sifatida dunyo miqyosida shuhrat qozongan. 1855 yilda ko'prik quruvchilar oldida eng murakkab vazifa turardi. Ular kengligi 1000 fut (300 m) bo'lgan Niagara daryosini bosib o'tishlari kerak edi. Tez suvlar iskala qurishga to'sqinlik qildi. Aksariyat erkaklar, jumladan, tajribali quruvchilar ham ishdan bosh tortdilar. Keyin J. Roeblingga ajoyib g'oya keldi - nega osma ko'prik qurmaslik kerak? Garchi muhandislar ko'prikni to'xtatib turish tamoyilini ancha oldin bilishgan bo'lsa-da, ular bunday ko'prik poezdlarni tashish uchun etarlicha barqaror bo'lishiga ishonishmagan. Aynan J. Roebling temir yo'l harakati uchun osma ko'priklardan foydalanish imkoniyatini birinchi bo'lib isbotlagan Mftjie osma ko'prikni qo'llash g'oyasi mashhur quruvchiga kelmagan, Niagara daryosining tez suvlari va boshqa ko'plab tez daryolar bo'lmagan. ko'prik qilingan.