问题 问答题

案例二:

已知某分部工程由A、B、C、D、E五项工作组成,其网络计划如下图所示,要求该分部工程必须在20天内完成。为了保证工期,需要进行赶工,相关的数据资料如下表所示。<<

[问题]

1.计算在标准工作情况下,该网络计划的各参数以及计划工期,并确定关键线路。

2.试确定在规定工期20天内完成该分部工程且增加的费用最少的网络优化方案。

答案

参考答案:

计算该分部工程的各工作的时间参数,见下图。

计划工期T=25天 关键线路为:A→B→D→E 2.在规定工期20天完工,应进行赶工,赶工对象是关键线路上的关键工作,且应从增加费用最少的关键工作开始。 (1)第一次压缩:在关键线路A→B→D→E中,D工作压缩费用变化率为4万元/天,最少,故压缩D工作,可压缩3天,压缩后的网络计划如图所示。

压缩后,关键线路为:A→B→D→E。 相应增加的费用为4×3=12万元,总费用为594万元,工期T1=22天。 (2)第二次压缩:在关键线路A→B→D→E中,D工作已经压缩,不能再压缩了,B工作压缩费用变化率为7万元/天,最少,故压缩B工作,最多可压缩2天,压缩后的网络计划如图所示。

按此方案压缩,从图中的计算可以得出,关键线路为A→B→C→E;工期T2=21天,相应增加的费用为7×2=14万元,总费用为608万元。此方案虽然可行,但实际上造成在节点④需要等工的情况,且造成相应的费用浪费,故不可取。因此,只压缩B工作1天,压缩后的网络计划如图所示。

压缩后,关键线路为:A→B→D→E和A→B→C→E。 相应增加的费用为7×1=7万元,总费用为601万元,工期T2=21天。 (3)第三次压缩:经过前两次压缩后,两条工作线路均为关键线路,可以进行压缩的工作有B、C和E三项,可选方案有两个:其一,同时压缩工作B、C各1天;其二,压缩工作E1天。 虽然B、C的费用变化率比E小,但需要同时压缩B、C工作才能满足规定的工期要求,这样压缩两项工作增加的费用必然比只压缩一项工作增加的费用多,因此,选择压缩 E工作,压缩1天,压缩后的网络计划如图所示。

压缩后,关键线路为:A→B→D→E和A→B→C→E。 相应增加的费用为8×1=8万元,总费用为609万元,工期T3=20天。 总之,经过几次压缩后,总工期控制在20天,相应增加的费用最少,达成目标要求。[考核内容] 建设项目网络计划的优化。

阅读理解
A very little boy was spending his Saturday morning playing in his sandbox. He had with him a plastic pail (桶) and a shiny, red plastic shovel (铲). In the  1  of creating roads and tunnels in the sand, he   2  a large rock in the middle of the sandbox.
The boy dug around the rock,  3  to move it off the dirt. At first, he wanted to carry it out of the sandbox with his hands; however, it was too heavy. Later, with much   4 , he pushed the rock across the sandbox by   5  his hands. When the boy got the rock to the   6  of the sandbox, he found that he couldn’t roll it up and   7  the little wall.   8 , the little boy pushed, but every time he thought he had made some   9 , the rock tipped (翻滚) and then fell back into the sandbox. The little boy pushed and pushed, but his only   10  was to have the rock roll back.
Finally he  11  tears. All this time the boy’s father watched from his living room window   12  the drama was unfolded. The moment the tears fell, a large   13  appeared across the sandbox. It was the boy’s father. Gently but   14 , he said, “Son, why didn’t you use all the strength that you had?”
Defeated, the boy   15  back, “I did! I did! I used all the strength that I had!”
“No, you didn’t. You didn’t ask me for help.” The father   16  down, picked up the rock and dropped it off the sandbox.
Do you have “rocks” in your life that need to be   17 ? Are you discovering that you don’t have   18  it takes to lift them? There is someone who is willing to give us the  19  we need. Maybe, it’s sometimes a good idea to ask others for   20  when we meet difficulties we can’t overcome.
小题1:
A.methodB.stepC.practiceD.process
小题2:
A.createdB.setC.discoveredD.brought
小题3:
A.tryingB.managingC.decidingD.competing
小题4:
A.thoughtB.struggleC.movementD.worry
小题5:
A.touchingB.shaking C.usingD.controlling
小题6:
A.bottomB.centerC.edgeD.front
小题7:
A.overB.downC.throughD.into
小题8:
A.DoubtedB.SurprisedC.PleasedD.Determined
小题9:
A.attemptB.progressC.effortD.decision
小题10:
A.hopeB.rewardC.pointD.purpose
小题11:
A.made outB.broke outC.burst intoD.rushed into
小题12:
A.soB.asC.untilD.before
小题13:
A.rockB.pictureC.figureD.shade
小题14:
A.surprisinglyB.doubtfullyC.kindlyD.firmly
小题15:
A.shoutedB.smiledC.calledD.asked
小题16:
A.reachedB.lookedC.fellD.put
小题17:
A.pushedB.dropped C.carriedD.removed
小题18:
A.whoB.whatC.whichD.where
小题19:
A.mindsB.spirits C.forceD.strength
小题20:
A.helpB.tipsC.adviceD.ideas
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