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1、刘克瑾河南工业大学土木建筑学院,土木工程专业英语,Lesson 3 Geometric design of highways,Text A Alignment Designalignment lanm()nt n.队列，线形；课文A 线路设计Text B Grades课文B 坡度Text C Sight Distance 课文C 视距,geometric,dmetrk adj.几何学的,1/9 The alignment of a road is shown on the plane view and is a series of straight lines called tangents
2、connected by circular curves.In modern practice it is common to interpose transition or spiral curves between tangents and circular curves.,Tangent tn(d)()nt n.数 切线，数 正切 adj.切线的，相切的；interpose ntpz vi.干预；插入；transition trnz()n;trn-;-s-n.过渡；转变；circular skjl adj.循环的；圆形的；spiral spar()l n.螺旋；旋涡；螺旋形之物 adj.
3、螺旋形的；盘旋的 vt.使成螺旋形；使作螺旋形上升 vi.盘旋；成螺旋形；螺旋形上升（过去式spiraled/spiralled，过去分词spiraled/spiralled，现在分词spiraling/spiralling，第三人称单数spirals，副词spirally）spiral curve 螺旋曲线circular curve 圆形曲线,1/9 The alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circula
4、r curves.In modern practice it is common to interpose transition or spiral curves between tangents and circular curves.翻译？,1/9 The alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circular curves.翻译公路的线路显示在平面图上，是一系列由圆曲线连接的切线而成。In modern pr
5、actice it is common to interpose transition or spiral curves between tangents and circular curves.翻译在现代实践（做法）中，在切线和圆曲线之间插入过渡线（螺旋线）是常见做法。,2/9 Alignment must be consistent.Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided;otherwise,accident hazards wil
6、l be created.Likewise,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 decrease
7、 possibility of future obsolescence.However,alignment without tangent is undesirable on two-lane roads because some drivers hesitate to pass on curves.Long,flat curves should be used for small changes in direction,as short curves appear as kink.Also horizontal and vertical alignment must be consider
8、ed together,not separately.For example,a sharp horizontal curve beginning near a crest can create a serious accident hazard.,2-1/9 Alignment must be consistent.Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided;otherwise,accident hazards will be creat
9、ed.Likewise,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.Consistent knsst()nt adj.连续的radii reda n.半径（radius的复数）compound curve 复合曲线sharp curve 急弯曲线；锐曲线；急弯；小半径曲线
10、transitiontrnzn n.过渡；转变,2-2/9 Long,flat curves are preferable at all times,as they are pleasing in appearance and decrease possibility of future obsolescence.However,alignment without tangent is undesirable on two-lane roads because some drivers hesitate to pass on curves.Long,flat curves should be
11、used for small changes in direction,as short curves appear as kink.Also horizontal and vertical alignment must be considered together,not separately.For example,a sharp horizontal curve beginning near a crest can create a serious accident hazard.flat curve 平缓曲线；平滑曲线；大曲率曲线preferable pr frbl adj.更好的，更
12、可取的；更胜一筹的pleasing pli:zi adj.令人愉快的；obsolescence,bsulesns n.废弃；Undesirable ndzarb()l adj.不良的；不受欢迎的；kink kk n.扭结；蜷缩 vt.使扭结 vi.扭结,2/9 Alignment must be consistent.Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided;otherwise,accident hazards will be creat
13、ed.Likewise,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 decrease possibili
14、ty of future obsolescence.However,alignment without tangent is undesirable on two-lane roads because some drivers hesitate to pass on curves.Long,flat curves should be used for small changes in direction,as short curves appear as kink.Also horizontal and vertical alignment must be considered togethe
15、r,not separately.For example,a sharp horizontal curve beginning near a crest can create a serious accident hazard.,3/9 A vehicle traveling in a curved path is subject to centrifugal force.This is balanced by an equal and opposite force developed through superelevation and side friction.From a highwa
16、y design standpoint,both superelevation and side friction cannot exceed certain maximums,and these controls place limits on the sharpness of curves that can be used with a design speed.,3/9 A vehicle traveling in a curved path is subject to centrifugal force.This is balanced by an equal and opposite
17、 force developed through superelevation and side friction.From a highway design standpoint,both superelevation and side friction cannot exceed certain maximums,and these controls place limits on the sharpness of curves that can be used with a design speed.centrifugal,sentrfjug()l;sentrfjg()l n.离心机；a
18、dj.离心的；centrifugal force 离心力side friction 横向摩擦superelevation,sju:p,elivein n.（铁路或公路的）超高;弯面倾斜度;道路弯面加倾度超高（Superelevation）公路平曲线路段，为抵销离心力，提高外侧路面之高度standpoint stn(d)pnt n.立场；观点sharpness:pnis n.锐利；锐度design speed 设计速度,4/9 Usually the sharpness of a given circular curve is indicated by its radius.However,fo
19、r alignment design,sharpness is commonly expressed in terms of degree of curve,which is the central angle subtended by a 100-ft length of curve.Degree of curve is inversely proportional to the radius.,4/9 Usually the sharpness of a given circular curve is indicated by its radius.However,for alignmen
20、t design,sharpness is commonly expressed in terms of degree of curve,which is the central angle subtended by a 100-ft length of curve.Degree of curve is inversely proportional to the radius.indicated nd,ketd v.表明（indicate的过去分词）；指出；显示Radius reds n.半径，半径范围；in terms of 依据；根据；用；按照；在方面；以措词Degree of curve
21、,曲率subtend sbtend vt.（弦、边）对（弧、角）；对向Ft-foot,英尺1ft=12in=0.3048m,5/9 Tangent sections of highways carry normal cross slope;curved sections are superelevated.Provision must be made for gradual change from one to the other.This usually involves maintaining the center line of each individual roadway at pr
22、ofile grade while raising the outer edge and lowering the inner edge to produce the desired superelevation.Where the alignment consists of tangents connected by circular curves,introduction of superelevation is begun on tangent before the curve is reached,and full superelevation is attained some dis
23、tance beyond the point of curve.,tangent section 切线段curved section 曲线段cross slope 横坡；横向坡度profile grade 纵断面坡度provision prv()n n.事先准备；防备（未来的需要）introduction of 引进；引入attained vt.取得，得到，获得（attain的过去式）point of curve 曲线起点;曲线始点,5/9 Tangent sections of highways carry normal cross slope;curved sections are sup
24、erelevated.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 superelevation.Where the alignment consists of tang
25、ents connected by circular curves,introduction of superelevation is begun on tangent before the curve is reached,and full superelevation is attained some distance beyond the point of curve.,6-1/9 If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp
26、 circular curve,riding is extremely uncomfortable.As the car approaches a curve,superelevation begins and the vehicle is tilted inward,but the passenger must remain vertical since there is no centrifugal force requiring compensation.When the vehicle reaches the curve,full centrifugal force develops
27、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 superelevation takes effect,further adjustment in position is required.This process is repeated in reverse order as the vehicle leaves the curve.When
28、 easement curves are introduced,the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal,6-2/9 force also develops gradually.By careful application of superelevation along the spiral,a smooth and gradual application of centrifugal forc
29、e can be had and the roughness(can be)avoided.approach prt n.方法；途径；接近;vt.接近；vi.靠近tilt tlt n.倾斜 vt.使倾斜；使翘起 vi.倾斜；翘起take effect 生效；起作用easement izm()nt n.缓和；减轻easement curve 缓和曲线far f adj.远的；久远的 adv.很；遥远地；到很远的距离；到很深的程度 n.远方,6-1/9 If a vehicle travels at high speed on a carefully restricted path made up
30、 of tangents connected by sharp circular curve,riding is extremely uncomfortable.As the car approaches a curve,superelevation begins and the vehicle is tilted inward,but the passenger must remain vertical since there is no centrifugal force requiring compensation.When the vehicle reaches the curve,f
31、ull 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 superelevation takes effect,further adjustment in position is required.,6-2/9 This process is repeated in reverse orde
32、r as the vehicle leaves the curve.When easement 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 superelevation along the spiral,a smooth and gradual
33、 application of centrifugal force can be had and the roughness(can be)avoided.Approach prt n.方法；途径；接近 vt.接近；着手处理 vi.靠近tilt tlt n.倾斜 vt.使倾斜；使翘起 vi.倾斜；翘起take effect 生效；起作用easement izm()nt n.缓和；减轻easement curve 缓和曲线,7/9 Easement curves have been used by the railroads for many years,but their adoption b
34、y highway agencies has become only recently.This is understandable.Railroad trains must follow the precise alignment of the tracks,and the discomfort described here can be avoided only by adopting easement curves.On the other hand,the motor-vehicle operator is free to alter his lateral position on t
35、he road and can provide his own easement curves by steering into circular curves gradually.However,this weaving within a traffic lane(but sometimes into other lane)is dangerous.Properly designed easement curves make weaving unnecessary.It is largely for safety reasons,then,that easement curves have
36、been widely adopted by highway agencies.,Railroads n.铁路（railroad的复数）；铁路部门Highway Agency 公路管理局Agency n.机构steering str n.操纵；指导；掌舵 v.驾驶；掌舵（steer的ing形式）weave wiv vi.迂回行进 vt.使迂回前进traffic lane 行车道；通车车道,7/9 Easement curves have been used by the railroads for many years,but their adoption by highway agencie
37、s has become only recently.This is understandable.Railroad trains must follow the precise alignment of the tracks,and the discomfort described here can be avoided only by adopting easement curves.On the other hand,the motor-vehicle operator is free to alter his lateral position on the road and can p
38、rovide his own easement curves by steering into circular curves gradually.However,this weaving within a traffic lane(but sometimes into other lane)is dangerous.Properly designed easement curves make weaving unnecessary.It is largely for safety reasons,then,that easement curves have been widely adopt
39、ed by highway agencies.,8/9 For the same radius circular curve,the addition of easement curves at the ends changes the location of the curve with relation to its tangents;hence the decision regarding their use should be made before the final location survey.The point of beginning of an ordinary circ
40、ular curve is usually labeled the PC(point of curve)or BC(beginning of curve).Its end is marked the PT(point of tangent)or EC(end of curve).For curves that include easements,the common notation is,as stationing increases:TS(tangent to spiral),SC(spiral to circular curve),CS(circular curve to spiral)
41、,and ST(spiral to tangent).,8/9 For the same radius circular curve,the addition of easement curves at the ends changes the location of the curve with relation to its tangents;hence the decision regarding their use should be made before the final location survey.The point of beginning of an ordinary
42、circular curve is usually labeled the PC(point of curve)or BC(beginning of curve).Its end is marked the PT(point of tangent)or EC(end of curve).For curves that include easements,the common notation is,as stationing increases:TS(tangent to spiral),SC(spiral to circular curve),CS(circular curve to spi
43、ral),and ST(spiral to tangent).label leb()l n.标签；vt.标注；贴标签于notation nte()n n.符号；Stationing n.驻军 v.驻扎（station的ing形式）;布点;定位,9/9 On two-lane pavements provision of a wilder roadway is advisable on sharp curves.This will allow for such factors as(1)the tendency for drivers to shy away from the pavement
44、edge,(2)increased effective transverse vehicle width because the front and rear wheels do not track,and(3)added width because of the slanted position of the front of the vehicle to the roadway centerline.For 24-ft roadways,the added width is so small that it can be neglected.Only for 30mph design sp
45、eeds and curves sharper than 22(degree)does the added width reach 2 ft.For narrower pavements,however,widening assumes importance even on fairly flat curves.Recommended amounts of and procedures for curve widening are given in Geometric Design for Highways.,provision prv()n n.事前准备advisable dvazb()l
46、adj.明智的，可取的，适当的shy away from 回避，退缩；躲避；transverse trnzvs;trnz-;-ns-n.横断面；贯轴；adj.横向的；横断的；贯轴的rear wheel 后轮；后车轮vehicle width 车宽track trk vi.追踪；vt.追踪；通过；循路而行；n.轨道；足迹，踪迹；小道slanted sl:ntid,slnt-adj.斜的；有倾向的 v.使倾斜（slant的过去式和过去分词）mph,em pi:eit abbr.每小时英里数（miles per hour）assume sjum vt.承担；假定；采取；,9/9 On two-lan
47、e pavements provision of a wilder roadway is advisable on sharp curves.This will allow for such factors as(1)the tendency for drivers to shy away from the pavement edge,(2)increased effective transverse vehicle width because the front and rear wheels do not track,and(3)added width because of the sla
48、nted position of the front of the vehicle to the roadway centerline.For 24-ft roadways,the added width is so small that it can be neglected.Only for 30mph design speeds and curves sharper than 22(degree)does the added width reach 2 ft.For narrower pavements,however,widening assumes importance even o
49、n fairly flat curves.Recommended amounts of and procedures for curve widening are given in Geometric Design for Highways.Finish,Lesson 3 Geometric design of highways,Text A Alignment Designalignment lanm()nt n.队列，线形；课文A 路线设计Text B Grades课文B 坡度Text C Sight Distance课文C 视距,1/9 The vertical alignment of
50、 the roadway and its effect on the safe and economical operation of the motor vehicle constitute one of the most important features of road design.The vertical alignment,which consists of a series of straight lines connected by vertical parabolic or circular curves,is known as the“grade line”.When t
