Automation in transportation

BRIDGES

The invention of the steam locomotive changed bridge building because stronger spans1 were

needed. Iron was first used for chain cables of a suspension bridge2 over the Tees River, in England, in 1741. The flooring3 was laid directly upon the cables. Abraham Darby and John Wilkinson built the first iron bridge over the Severn River at Coalbrookdale, England, in 1779. This 100-foot (30- meter) arch bridge is still in service. Thomas Telford built the first modern iron arch bridge in 1813.

It is Craig Ellachie Bridge over the Spey River, Scotland, with a 150-foot (46-meter) span. It was

not built up of cast-iron blocks in imitation of masonry as were previous iron arch bridges but was the first to use an arch made up of iron trusses4. In 1819 – 1824 Telford built the forerunner of the modern suspension bridges – the 570-foot (174-meter) span over Menai Strait in Wales. It had wrought-iron5 chains for cables.

The first to design railroad bridges was George Stephenson, who with his son Robert invented

the Rocket, the first practical locomotive. Robert Stephenson built the Britannia Tubular Bridge over Menai Strait in 1846. Its two boxlike tubes were made of iron plates riveted6 together. Many truss designs were patented in the 1850s for railroad bridges. After numerous failures of cast-iron bridges, wrought iron was used, then steel.

The first bridge to use steel extensively was the triple-arched Eads Bridge over the Mississippi

at St.Louis, Mo., in 1874. It was an important link in the transcontinental railroad and made St.Louis a crossroads. This bridge was named after James B. Eads who designed it and was in charge of its construction. The modern era of steel arch building began in the 20th century. The Bayonne Bridge, completed in 1931 over Kill van Kull between New York and New Jersey, has a 1,652-foot (504- meter) span. Australia’s Sydney Harbor Bridge, finished in 1932, is only 2 feet (0.6 meter) shorter.

At the turn of the 20th century, the construction of masonry arch bridges reached its peak. Then the more economical and easier to use concrete became common for arch bridges. Later, reinforced concrete7 and then prestressed concrete8 were used.

Notes:

1 span – пролёт моста

2 suspension bridge – висячий мост

3 flooring – настил

4 truss – балка, ферма (моста)

5 wrought iron – кованое железо

6 to rivet – приковывать

7 reinforced concrete – железобетон

8 prestressed concrete – предварительно напряжённый бетон

The most sophisticated applications of automation in transportation have been made in the

guidance and control of aircraft and spacecraft. Other applications include railroad operations and automatic traffic control.

Aviation. Automated systems combining radar, computers, and auxiliary electronic equipment

have been developed to control the ever-increasing volume of air traffic. Air traffic controllers at

large airports depend on such systems to direct the continuous flow of incoming and outgoing

airplanes. They can pinpoint the position of every plane within 50 miles (80 kilometers) of the

airfield on a special display screen of the radar unit. This information allows the controllers to select the safest route for pilots to follow as they approach and leave the airport. Many of the systems of the aircraft itself are automated. Oxygen masks, for instance, automatically drop down from overhead compartments when the cabin pressure becomes too low. Most modern planes have an automatic pilot that can take over for the human pilot. Commercial passenger planes are usually equipped with an automatic landing system that can be used when runway visibility is poor. The system employs radio beams from the ground to operate an instrument on board the plane. By watching this instrument, a pilot can determine the exact position of his craft in relation to the landing strip.

Railroads. Automation has become an important factor in railroad operations. The management

of rail yards1 has been facilitated by computerized systems that integrate the signaling and

switching2 functions of classification yards, where freight trains are sorted and assembled.

Electronic scanners read color-coded identification labels on all freight cars entering a classification yard and relay the information to yard computers that assign the cars to the proper track.

Automation has also been adopted by many passenger rail lines. In a number of systems, automatic equipment is used so extensively that the function of the train operator has been reduced to simple on and off operations during station stops. Since commands from automatic controls are continuously fed to other automatic mechanisms in response to information collected by sensors strategically positioned on the engine and track, human control of the engine is only required in an emergency.

An impressive example of automated rail transportation is the Bay Area Rapid Transit (BART)

system serving the San Francisco-Oakland area of California. BART consists of more than 75 miles (121 kilometers) of track and about 100 trains operating between 33 stations at peak hours. Both the operation of trains and ticketing of passengers are fully automated. As a train enters a station, it automatically transmits its identification and destination to the control center and to a display board for passengers to see. The control center, in turn, sends signals to the train that regulate its time in the station and its running time to the next destination. An ideal schedule is established every morning and, as the day progresses, the performance of each train is compared with that schedule.

The performances of individual trains are then adjusted as required. The entire BART system is

controlled by essentially one computer. There is an identical backup computer that can assume

control if necessary.

Notes:

1 (classification) yard – сортировочная станция

2 switching – маневровая работа

Дата добавления: 2017-02-01