本科毕业设计（论文）
专业名称： | 土木工程专业（道路与桥梁） |
年级班级： sliverlight是什么 | 道桥08-5班 |
学生姓名： | encore une fois |
指导教师： | |
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二○一二年五月十八日
Geometric Design of Highways
The road is one kind of linear construction ud for travel. It is made of the roadbed, the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility.
jyaThe roadbed is the ba of road surface, road shoulder, side slope, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the ba of travel, must guarantee that it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.
The road surface is the surface of road. It is single or complex structure built with mixture. The road surface require being smooth, having enough intensity, good stability and anti-slippery function. The quality of road surface directly affects the safe, comfort and the traffic.
Highway geometry designs to consider Highway Horizontal Alignment, Vertical Alignment two kinds of linear and cross-ctional composition of coordination, but also pay attention to the smooth flow of the line of sight, etc. Determine the road geometry, consider the topography, surface features, rational u of land and environmental protection factors, to make full u of the highway geometric components of reasonable size and the linear combination.高考怎样查分
1.Alignment Designheadcount budget
The alignment of a road is shown on the plane view and is a ries of straight lines called tangents connected by circular. In modern practice it is common to interpo transition or spiral curves between tangents and circular curves.
Alignment must be consistent. Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided; otherwi, accident hazards will be created. Likewi, placing circular curves of different radii end to end (compound curves) or having a short tangent between two curves is poor practice unless suitable transitions between them are provided. Long, flat curves are preferable at all times, as they are pleasing in appearance and decrea possibility of future obsolescence. However, alignment without tangents is undesirable on two-lane roads becau some drivers hesitate to pass on curves. Long, flat curves should be ud for small changes in direction, as short curves appear as “kink”. Also horizontal and vertical alignment must be considered together, not parately. For example, a sharp horizontal curve beginning near a crest can create a rious accident hazard.
allantoinA vehicle traveling in a curved path is subject to centrifugal force. This is balanced by an equal and opposite force developed through cannot exceed certain maximums, and the controls place limits on the sharpness of curves that can be ud with a design speed. Usually the sharpness of a given circular curve is indicated by its radius. However, for alignment design, sharpness is commonly expresd in terms of degree of curve, which is the central angle subtended by a 100-ft length of curve. Degree of curve is inverly proportional to the radius.
uriTangent ctions of highways carry normal cross slope; curved ctions are super 箱子的英语elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center line of each individual roadway at profile grade while raising the outer edge and lowering the inner edge to produce the desired super elevation is attained some distance beyond the point of curve.
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If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp circular curve, riding is extremely uncomfortable. As the car approac
hes a curve, super elevation begins and the vehicle is tilted inward, but the pasnger must remain vertical since there is on centrifugal force requiring compensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider outward from his vertical position. To achieve a position of equilibrium he must force his body far inward. As the remaining super 成都信息工程学院录取查询elevation takes effect, further adjustment in position is required. This process is repeated in rever order as the vehicle leaves the curve. When eament curves are introduced, the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal force also develops gradually. By careful application of super elevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided.
