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1、NOTES OF LESSONCE2303Railways, Airport and Harbour Engineering The Definition of Railway Rolling StockIt is always useful at the outset of consideration of a subject to pause for a moment and to ponder the definitions, attributes range and scope of the matter.Rolling stock used on railways in the ea
2、rliest days evolved from carriages and wagons which ran on highways to carry both people and bulk materials.As early as the sixteenth century wooden wheeled carts were used in mines and quarries running on longitudinal timber rails. With the progressive evolution of the skills and crafts of the whee
3、lwright, metalworker and the ironmaker, wheels improved through various phases from simple roughturned wooden spools through spoked and rimmed construction to fully cast and turned metal wheels.Similarly, body construction and springing, particularly for passenger carrying vehicles, relied very heav
4、ily on the experience gained in the construction of stagecoaches in the seventeenth and eighteenth centuries. At the end of the eighteenth century, horse drawn trams running on metal rails began to appear in a number of European cities. These horse drawn tramways were literally to pave the way for d
5、evelopment of railways when steam power began to be developed early in the 1800s. One has only to look at illustrations of early passenger coaches to see how closely they resemblethe road vehicles of the previous century.As railway experience was gained, the design of rolling stock also evolved. Spr
6、inging, body structure, wheels and axles all are subject to varying loads and stresses, when comparing slower speeds on rough roads to much faster speeds on railways, with a comparatively smoother ride.Railway rolling stock generally runs on hard wheels on hard rails. The wheels are not only support
7、ed by the rails but are guided by them. The only exception to this is for a small number of metros where rubber tyres have been introduced. In this case the supporting function of the rail may be separated from the guiding function.In all cases railway rolling stock will transmit vertical, horizonta
8、l and longitudinal forces to the track and its supports. Most railways have adopted twin rails and flanged wheels. Forces are transmitted to the railstructure either by direct bearing on the rail top from the wheel tyre, or by bearing laterally through the flange, or by longitudinal friction. Potent
9、ial overturning forces, caused by centrifugal force on curves, coupled with wind forces on exposed locations are resisted by vertical dead weight andsuper-elevation or cant on curves.The Range of Railway Rolling StockToday there is a very wide range of rolling stock used throughout the worldon diffe
10、rent railways. This range includes the following basic types: Locomotives Freight wagons Passenger coaches Multiple units (with motive power in-built) Metro cars (usually multiple units) Light rail/Trams (usually articulated units) Rail mounted machines (cranes, tampers etc.) Inspection and maintena
11、nce trolleysThe Objectives in Station PlanningIn planning any station the following objectives need to be kept very muchin mind: Attractiveness in appearance. Free movement of passengers. Safe evacuation in emergency. Access for the disabled. Access for emergency services. Safe accumulation and disp
12、ersal of crowds. Reliable operation of train service. Resilience to failure. Cost-effective investment.Planning for Normal OperationThe degree to which the business is prepared to invest in providing space purely for the added comfort of passengers must be decided by each railway system based on its
13、 own market position and objectives.The starting point for any station planning is the demand forecast. This must be accompanied by a detailed knowledge of the likely train frequency from each platform and the time staff would need to take action when problems arise. Given working assumptions, it is
14、 then possible to determinehow many people are likely to have accumulated within a particular area before control measures can be instituted.The operator must determine his own relative values for key variables which combine to determine the minimum size and capacity for any element of a station.The
15、se will include: time needed to become aware of a problem. staff reaction and decision time. action implementation time. accumulation rate for passengers. maximum density for safety.The frequency and destination pattern of the train service is also a key factor in the sizing of station infrastructur
16、e. Assuming, for instance, that the total staff reaction time is effectively five minutes and that the normal peak service is at five minute intervals, capacity at the platform must allowfor at least twice the normal numbers expected in the peak.Capacity RequirementsIt is recommended that the follow
17、ing limits should be applied to station areas for demand levels under normal peak conditions:Platforms, ticket halls and concourses 0.8 sqm per personPassageways one way 50 persons per minute/m width two way 40 persons per minute/m widthFixed Stairways one way 35 persons per minute/m width two way 2
18、8 persons per minute/m widthTo allow for peaks within a peak it is wise to use the calculated peak fifteen-minute flow figure, which can be derived from the one-hour figure by multiplying by 0.3.Similarly the peak five-minute flow figure can be derived by multiplying the fifteen-minute figure by 0.4
19、. This five-minute figure should be used when testing the layout tight spots to ensure that dangerous situations do not occur during the short lived period when crowding exceeds desirable levelsat a restricted localised point.The capacity of entrances and exits to street level should follow the guid
20、elines above. From subsurface ticket halls/concourse areas there should be at least two exits to the street each of which must be able to take the full peak level demand albeit under crowded conditions.Locations which are fed by exits from stations need to be examined to ensure that no bottle-necks
21、exist immediately outside station buildings.This is particularly important where stations exit into Local Authority subways, shopping malls or where sporting events are likely to produce tidal wave crowding.The Evolution of Steam Motive PowerAs has been mentioned previously, the harnessing of steam
22、power in the late eighteenth and early nineteenth centuries was the springboard for the development of railways throughout the world. The concept of running hard rimmed flanged wheels on narrowmetal rails had been tried out in the minesand quarries and found to be both workable and advantageous.The
23、main limitation to the effectiveness of using plate-ways, rail-ways or tram-ways was the adequate provision of haulage power or what became known as motive power.Walking pace motive power was first provided by men and horses and later in some places by stationary engines driving winches for cable ha
24、uled cars. As the design of wheels, axles and bearings steadily improved, towards the end of the eighteenth century, heavier loads could be moved and railborne movable steam locomotives became a possibility.The first steam hauled train was operated by Richard Trevithicks steam locomotive in South Wa
25、les in 1804. While this locomotive seems to have worked quite well on a mine tramway, the cast iron plates that formed the track proved to be inadequate for the heavier loads and impacts.Hard on its heels, William Hedleys Puffing Billy built in 1813, ran on a tramway near Newcastle-on-Tyne giving su
26、ccessful service for over forty years.The first use of steam for a passenger train was George Stephensons Locomotion on the Stockton and Darlington Railway in 1825. There is a wall plaque at the original railway station at Stockton whichreads:The first public railway to use steam motive power exclus
27、ively and to run a regular passenger service was the Liverpool and Manchester Railway which commenced operations in 1829. This railway was perhaps the first to have the essential elements of a modern railway. All trains were locomotivehauled, running to a timetable, operated by company staff and onl
28、y stopping at stations manned by its own staff. The railway linked the two cities and was only 38 miles long, taking about two hours six minutes to do the journey. This average speed of 18 mph seems extremely slow to us but whencompared to walking, running, or going by narrowboat or stagecoach, wasa
29、 substantial improvement.What is even more amazing is that fourteen short years later Daniel Gooch, locomotive superintendent of the Great Western Railway, drove Prince Albert home from Bristol to London in about the same time, adistance of about 118 miles! The average city to city speed on that jou
30、rney of 57 mph is still remarkable and could not be achieved today by driving from Bristol to London, even with the fastest car, without breaking the speed limits!During the rest of the nineteenth century railways continued to develop and spread to all parts of the civilised world. With this develop
31、ment both steam locomotives and all types of rolling stock grew in size and complexity.Steam power dominated traction on most of the worlds railways in the first hundred years or so. Indeed, until the 1880s, steam was the only form of motive power that was considered viable for railways. Even the so
32、 called atmospheric railways still relied on stationary steam engines to providetheir power.In the very earliest days, even at the time of George Stephensons Rocket, boilers were fitted with multiple tubes, water space round a fire box and a fire which was drawn by the exhaust steam blasted up the c
33、himney. Most locomotives had two cylinders linked to the large driving wheels by external connecting rods.Cylinders were normally inclined at an angle to the horizontal and drove only one pair of wheels. Eventually cylinders were placed horizontally in a forward location and the driving power was li
34、nked to all the driving wheels by various cranks and connecting rods.There was also a great deal of activity in the design and evolution of valve gear, slides, pumps and pistons which all added to both the efficiency and the complexity of steam locomotives. Steam traction is simple in essence and so
35、me complexity led to more difficulties and problems than were solved.The invention of super-heating of steam in the late nineteenth century led to adoption of this feature in later steam locomotives, giving rise to higher efficiency but also a need for better maintenance, particularly of boilers and
36、 tubes.Early underground railways adopted steam power for hauling train because at that time there did not appear to be any practical alternative.The first underground railway in the world was opened by the Metropolitan Railway Company in 1863 between Paddington and Farringdon, London. By that time
37、many hundreds of miles of main linerailway had been built around the world and over thirty years experience had been gained in the design, manufacture and operation of steam locomotives.This original section of the new line, together with its later extensions (now the Circle Line), was constructed u
38、sing the cut-and-cover method. As the construction was only at a shallow depth, openings were left wherever possible in an attempt to ensure steam, smoke and fumes were adequatelyventilated.The original intention was to use conventional steam locomotives on this line burning no fuel on the undergrou
39、nd sections but relying on them,head of steam and heating up only at the end of the comparatively short underground section.When the line was opened it was found that conventional locomotives caused distress to passengers and staff due to the discharge of carbonic oxide gases. Some relief of the pro
40、blem was found in construction of condensing engines but clearly some other form of motive power would be desirableunderground. The London commuter had to suffer the inconvenience of steam locomotives in confined spaces for another three decades or so beforea satisfactory alternative was found.The A
41、dvent of Electric TractionThe possibility of electric traction was first demonstrated by a Scotsmancalled Davidson in 1834 but it was not until the Berlin Exhibition of 1879that the idea was developed far enough to show that it could be a practicalchallenger to steam.The obvious advantages of electr
42、ic traction over steam for undergroundrailways attracted the attention of many engineers and operators aroundthe world in the last decade of the nineteenth century.The first Tube line to be built in London was the City and SouthLondon Railway between King William Street and Stockwell in 1890 usingel
43、ectric traction. This was followed within ten years by the constructionof the Central London Railway from Shepherds Bush to Bank, also usingelectric traction. Other tube lines followed rapidly, all of which wereincorporated into todays London Underground.Most of these early tube lines followed the m
44、ain line practice of a singlelocomotive pulling non-powered carriages or cars. The City & SouthLondon locomotives were small four wheeled vehicles whereas the CentralLondon Locomotives were a much larger camel back design with fourdriving axles mounted in two bogeys.During the first decade of the tw
45、entieth century all of the London tubelines departed from the principle of single locomotive hauling to using anumber of motorcars along the length of the train. This has considerableadvantage for rapid transit trains, not the least of which is to distributeboth traction and braking along the full l
46、ength of the train. This has theeffect of improving both acceleration and braking, which is important onlines where there are frequent stops.For the same reasons many main line railways have now come away fromthe use of locomotives for suburban and stopping services and have adoptedmultiple units wi
47、th motors distributed along the length of the train.Development of Electric TractionThe suburban and underground railways that were built or electrified inthe early part of the twentieth century adopted a medium voltage directcurrent supply system which involved fairly costly fixed equipment but kep
48、t34 Practical Railway Engineeringthe locomotives relatively simple and cheap. A large number of transformersub-stations were involved with comparatively heavy conductor rails setat track level. Technology was very similar to the early electric tramwayswhich were also powered with direct current.In the UK, London Underground and a large part of the SouthernRegion of British Railways adopted DC electric traction many years beforethe rest of BR converted from steam power to diese
