網(wǎng)絡(luò)計(jì)劃技術(shù)講義-資料下載頁(yè)
2025-02-08 14:32本頁(yè)面
【正文】 theconstraintthatprojectdurationmustbelessthanorequaltothetimedesiredbytheprojectmanager.n Thedecisionstobemadearethefollowing:1. Thestarttimeofeach2. Thereductioninthedurationofeachactivitydueto活動(dòng)工期的減少量3. Thefinishtimeoftheproject(mustnotexceed40weeks).n Theconstraintsare:1. TimeReduction≤MaxReduction(foreachactivity).2. ProjectFinishTime≤DesiredFinishTime.3. ActivityStartTime≥ActivityFinishTimeofallpredecessors(foreachactivity).4. ProjectFinishTime≥FinishTimeofallimmediatepredecessorsoffinishnode.Spreadsheet ModelMr. Perty’s Conclusionsn Theplanforcrashingtheprojectonlyprovidesa50percentchanceofactuallyfinishingtheprojectwithin40weeks,sotheextracostoftheplan($140,000)isnotjustified.Therefore,Mr.Pertyrejectsanycrashingatthisstage.n Theextracostofthecrashingplancanbejustifiedifitalmostcertainlywouldearnthebonusof$150,000forfinishingtheprojectwithin40weeks.Therefore,Mr.PertywillholdtheplaninreservetobeimplementediftheprojectisrunningwellaheadofschedulebeforereachingactivityF.n Theextracostofpartorallofthecrashingplancanbeeasilyjustifiedifitlikelywouldmakethedifferenceinavoidingthepenaltyof$300,000fornotfinishingtheprojectwithin47weeks.Therefore,Mr.PertywillholdthecrashingplaninreservetobepartiallyorwhollyimplementediftheprojectisrunningfarbehindschedulebeforereachingactivityForactivityJ.Scheduling and Controlling Project Costsn PERT/Costisasystematicprocedure(normallyputerized)tohelptheprojectmanagerplan,schedule,andcontrolcosts.n Assumption:AmonassumptionwhenusingPERT/Costisthatthecostsofperforminganactivityareincurredataconstantratethroughoutitsduration.Budget for Reliable’s ProjectActivity EstimatedDuration(weeks)EstimatedCostCostperWeekofItsDurationA 2 $180,000 $90,000B 4 320,000 80,000C 10 620,000 62,000D 6 260,000 43,333E 4 410,000 102,500F 5 180,000 36,000G 7 900,000 128,571H 9 200,000 22,222I 7 210,000 30,000J 8 430,000 53,750K 4 160,000 40,000L 5 250,000 50,000M 2 100,000 50,000N 6 330,000 55,000PERT/Cost Spreadsheet (Earliest Start Times)PERT/Cost Spreadsheet (Earliest Start Times)PERT/Cost Spreadsheet (Latest Start Times)PERT/Cost Spreadsheet (Latest Start Times)Cumulative Project CostsPERT/Cost Report after Week 22Activity BudgetedCost PercentCompletedValueCompletedActualCosttoDateCostOverruntoDateA $180,000 100% $180,000 $200,000 $20,000B 320,000 100 320,000 330,000 10,000C 620,000 100 620,000 600,000 –20,000D 260,000 75 195,000 200,000 5,000E 410,000 100 410,000 400,000 –10,000F 180,000 25 45,000 60,000 15,000I 210,000 50 105,000 130,000 25,000Total $2,180,000 $1,875,000 $1,920,000 $45,000四、網(wǎng)絡(luò)優(yōu)化得到初始的計(jì)劃方案，但通常要對(duì)初始方案進(jìn)行調(diào)整與完善。根據(jù)計(jì)劃目標(biāo)，綜合考慮資源和降低成本等目標(biāo)，進(jìn)行網(wǎng)絡(luò)優(yōu)化，確定最優(yōu)的計(jì)劃方案。 資源優(yōu)化做法：1）優(yōu)先安排關(guān)鍵工序所需的資源。2）利用非關(guān)鍵工序的時(shí)差，錯(cuò)開(kāi)各工序的開(kāi)始時(shí)間。 3）統(tǒng)籌兼顧工程進(jìn)度的要求和現(xiàn)有資源的限制，多次綜合平衡。下面列舉一個(gè)拉平資源需要量最高峰的實(shí)例。在例 5中，若加工工人為 65人，并假定這些工人可完成這 5個(gè)工序任一個(gè)，下面來(lái)尋求一個(gè)時(shí)間 資源最優(yōu)方案。如表 1216所示： 表 1216工序 需要人數(shù)最早開(kāi)始時(shí)間所需時(shí)間時(shí)差d 58 60 20 0f 22 70 18 47g 42 80 3 0h 39 100 15 20i 26 110 25 0 若上述工序都按最早開(kāi)始時(shí)間安排，那么從第 60天至第 135天的 75天里，所需的機(jī)械加工工人人數(shù)如圖 1217所示。在圖的上半部中，工序代號(hào)后的數(shù)字是人數(shù)，線下面的數(shù)字是非關(guān)鍵工序時(shí)差長(zhǎng)度。圖的下半部表示從第 60天至 135天內(nèi)的 75天里，所需機(jī)械加工工人數(shù)，這樣的圖稱為資源負(fù)荷圖。58人 64人80人 81人42人26人65人60 80 100 120 1302 74 635 f(22人）18h(39人 )15 d(58人） i(26人） g(42人）3020 25圖 1217同時(shí)我們應(yīng)優(yōu)先安排關(guān)鍵工序所需的工人，再利用非關(guān)鍵工序的時(shí)差，錯(cuò)開(kāi)各工序的開(kāi)始時(shí)間，從而拉平工人需要量的高峰。經(jīng)過(guò)調(diào)整，我們讓非關(guān)鍵工序 f從第 80天開(kāi)始，工序 h從第 110天開(kāi)始。找到了時(shí)間 資源優(yōu)化的方案，如圖 1218所示，在不增加工人的情況下保證了工程按期完成。2 4 6 753 f(22人） h(39人） d(58人） i(26人） g(42人）工人數(shù)65人60 80 100 120 13058人42人64人26人65人 圖 1218演講完畢，謝謝觀
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