《交通工程专业英语翻译》.docx

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1、DesignoftheAlignment线形设计Thealignmentofahighwayiscomposedofverticalandhorizontalelements.Theverticalalignmentincludesstraight(tangent)highwaygradesandtheparaboliccurvesthatconnectthesegrades.Thehorizontalalignmentincludesthestraight(tangent)sectionsoftheroadwayandthecircu

2、larcurvesthatconnecttheirchangeindirection.公路线形包括平曲线和竖曲线元素。竖曲线包括直坡线（切线）和连接这些直坡线的抛物线。平曲线包括公路的直线部分（切线）和连接两直线并转向的圆曲线。Thedesignofthealignmentdependsprimarilyonthedesignspeedselectedforthehighway.Theleastcostlyalignmentisonethatgenerallytakestheformofthenaturaltopography.Itis

3、notalwayspossibletoselectthelowestcostalternativebecausethedesignerhastoadheretocertainstandardsthatmaynotexistonthenaturaltopography.线形的设计取决于公路的设计速度。最经济的线形是沿着自然地形展线。现实中设计师往往不能选择造价最低的方案，因为他们必须遵循特定的技术标准，而这些标准在自然地形中也许难以达到。Itisimportantthatthealignmentofagivensectionhascons

4、istentstandardstoavoidsuddenchangesintheverticalandhorizontallayoutofthehighway.Itisalsoimportantthatbothhorizontalandverticalalignmentsbedesignedtocomplementeachother,sincethiswillresultinasaferandmoreattractivehighway.重要的是给定部分的线形必须符合规范来避免公路在水平和竖直布局上产生突变。同样重要的是设计的平曲线和竖曲

5、线要相互协调，因为这样才能设计出安全并更有吸引力的公路。Onefactorthatshouldbeconsideredtoachievecompatibilityistheproperbalancingofthegradesoftangentswithcurvaturesofhorizontalcurvesandthelocationofhorizontalandverticalcurveswithrespecttoeachother.Forexample,adesignthatachieveshorizontalcurveswithl

6、argeradiiattheexpenseofsteeporlonggradesisapoordesign.Similarly,ifsharphorizontalcurvesareplacedatornearthetopofpronouncedcrestverticalcurvesoratornearthebottomofapronouncedsagverticalcurve,ahazardousconditionwillbecreatedatthesesectionsofthehighway.Thus,itisimportanttha

7、tcoordinationoftheverticalandhorizontalalignmentsbeconsideredattheearlystagesofpreliminarydesign.为提高协调性应考虑的因素之一是保持直线坡度和曲线曲率均衡，处理好平曲线和竖曲线之间的相互位置。例如，大半径平曲线搭配长陡纵坡是一种较差的设计。同样，如果在凸形竖曲线的顶部及附近或在凹形竖曲线底部及附近设置小半径平曲线，那该路段就会变得很危险。因此，在初步设计阶段综合考虑平纵曲线很重要。Theverticalalignmentofahighwayc

8、onsistsofstraightsectionsknownasgrades,ortangents,connectedbyverticalcurves.Thedesignoftheverticalalign