市政工程施工组织与管理课件 模块3 任务五 优化网络计划（费用优化1）-（原译双语）

第四节网络计划优化

Section4:NetworkPlanOptimization二、费用优化

II.CostOptimization1.费用优化定义：1.Definitionofcostoptimization:

费用优化又称工期成本优化是指寻求工程总成本最低时的工期安排或按要求工期寻求最低成本的计划安排过程。本小节主要讨论总成本最低时的工期安排。Costoptimization,alsoknownasduration-costoptimization,referstotheprocessofseekingthelowesttotalcostoftheprojectbyarrangingtheduration,orseekingthelowestcostforaspecifiedduration.Thissectionmainlydiscussestheplanningoftheconstructionperiodthatachievesthelowesttotalcost.1)费用和工期的关系1)Relationshipbetweencostandconstructionperiod

安装工程费用主要由直接费用和间接费用组成一般情况下缩短工期会引起直接费用的增加和间接费用的减少,延长工期则会起直接费用的减少和间接费的增加。Theinstallationcostismainlycomposedofdirectandindirectcosts.Generally,shorteningtheconstructionperiodwillleadtoanincreaseindirectcostsandadecreaseinindirectcosts,whereasextendingtheconstructionperiodwillleadtoadecreaseindirectcostsandanincreaseinindirectcosts.费用优化又叫工期-成本优化Costoptimizationisalsoknownasconstructionperiod-costoptimization)工期与费用关系曲线Curveoftherelationshipbetweenconstructionperiodandcost TC-最短工期TO-优化工期TN-正常工期TC-ShortestConstructionPeriod|TO-OptimizedConstructionPeriod|TN-NormalConstructionPeriod2）费用优化的步骤和方法：2)Stepsofcostoptimization费用优化的基本思路不断地在网络计划中找出直接费用率(或组合直接费用率)最小的关键工作,缩短其持续时间时考虑间接费随工期缩短而减少的数值,最后求得工程总成本最低时的最优工期安排或按要求工期求得最低成本的计划安排。Thebasicideainvolvesconstantlyidentifyingcriticalactivitieswiththelowestdirectcostrate(orcombineddirectcostrate)inthenetworkplanning.Whencompressingdurations,payattentiontothecorrespondingindirectcostreductions.Thisprocessultimatelydetermineseithertheoptimalconstructionperiodschedulewiththelowesttotalcostorthelowest-costplanningscheduleunderrequiredconstructionperiod.按照上述基本思路费用优化可按以下步骤进行:Giventheidea,thecostoptimizationprocesscanbeimplementedthroughthefollowingsteps:①按工作的正常持续时间确定计算工期和关键线路.①Determinetheconstructionperiodandcriticalpathbasedonthenormaldurationofeachtask.②计算各项工作的直接费用率直接费用率的计算按式(4.1)进行.②Calculatethedirectcostrateforeachtask.Thecalculationofthedirectcostrateiscarriedoutaccordingtoformula(4.1).

直接费用率∆C=（CC-CN）/（DN-DC）(4.1)Directcostrate∆C=(CC-CN)/(DN-DC)(4.1)式中∆C:i一j工作的直接费用率,Intheformula,∆Cisthedirectcostratefortasksi-j;CC:

i一j工作的最短持续时间的直接费用,CCisthedirectcostfortheshortestdurationoftasksi-j;CN:

i一j工作的正常持续时间的直接费用,CNisthedirectcostforthenormaldurationoftasksi-j;DN:

i一j工作的正常持续时间,DNisthenormaldurationoftasksi-j;DC:

i一j工作的最短持续时间。andDCistheshortestdurationoftasksi-j.③当只有一条关键线路时，应找出直接费用率最小的一项关键工作，作为缩短持续时间的对象。③Whenthereisonlyonecriticalpath,identifythecriticaltaskwiththelowestdirectcostrateasthetargetfordurationreduction.当有多条关键线路时,应找出组合直接费用率最小的一组关键工作,作为缩短持续时间的对象。Whentherearemultiplecriticalpaths,selectthegroupofcriticalactivitieswiththelowestcombineddirectcostrateasthetargetfordurationcompression.④对于选定的压缩对象(一项关键工作或一组关键工作)首先比较其直接费用率或组合④Fortheselectedshorteningobject(akeytaskoragroupofkeytasks),firstcompareitsdirectcostrateorcombineddirectcostratewiththeproject’sindirectcostrate:直接费用率与工程间接费用率的大小:Themagnitudeofthedirectcostratecomparedtotheindirectengineeringcostrate:a.如果被压缩对象的直接费用率或组合直接费用率大于工程间接费用率,说明压缩关键工作的持续时间会使工程总费用增加，此时应停止缩短关键工作的持续时间,在此之前的方案即为优化方案。a.Ifthedirectcostrateorcombineddirectcostrateofthetargetisgreaterthantheproject'sindirectcostrate,itindicatesthatreducingthedurationofcriticaltaskswouldincreasethetotalprojectcost.Inthiscase,stopreducingthedurationofcriticaltasks.Theplanbeforethispointistheoptimalplan.b.如果被压缩对象的直接费用率或组合直接费用率等于工程间接费用率,说明压缩关键工作的持续时间不会使工程总费用增加,故应缩短关键工作的持续时间。b.Ifthedirectcostrateorcombineddirectcostrateofthetargetequalstheproject'sindirectcostrate,itindicatesthatshorteningthedurationofthecriticaltaskwillnotincreasetheproject'sexpenses.Therefore,thedurationofthecriticaltaskshouldbereduced.c.如果被压缩对象的直接费用率或组合直接费用率小于工程间接费用率,说明压缩关键工作的持续时间会使工程的总费用减少,故应缩短关键工作的持续时间。Ifthedirectcostrateorcombineddirectcostrateofthetargetislessthantheproject'sindirectcostrate,itindicatesthatshorteningthedurationofthecriticaltaskwillreducetheproject'stotalcosts.Therefore,thedurationofthecriticaltaskshouldbereduced.⑤当需要缩短关键工作的持续时间埘,其缩短值的确定必须符合下列两条原则:⑤Whenitisnecessarytoshortenthedurationofcriticaltasks,thedeterminationoftheshorteningvaluemustcomplywiththefollowingtwoprinciples:a.缩短后工作持续时间不能小于其最短持续时间。a.Theshortenedtaskdurationmustnotbelessthantheminimumduration.b.缩短持续时间的工作不能变成非关键工作。b.Thetaskwithshorteneddurationmustnotbecomeanon-criticaltask.⑥计算关键工作持续时间缩短后相应增加的总费用。⑥Calculatethetotalcostincreasecorrespondingtotheshorteningofthecriticaltaskduration.⑦重复上述3~6,直至计算工期满足要求工期或被压缩对象的直接费用率或组合直接费用率大于工程间接费用率为止。⑦Rep