武汉理工大学-863工程项目管理课件-工程项目计划系统

1、工程项目计划系统PROJECT PLANNING在总目标确定后，分析总目标能否实现计划同时又是目标的分解过程计划是实施的指南和实施控制的依据业主和项目的其他方面需要利用计划的信息一、计划的作用One distinguishing feature of projects is that each is tailored toward some unique end-item or result. That uniqueness implies that every project must be defined anew and a scheme created telling everyone

2、 involved what to do.Three things occur in the planning and control process: (1) During the conception and definition phases a plan is prepared specifying the project requirements, work tasks, responsibilities, schedules, and budgets; (2) during the execution phase the plan is compared to actual pro

3、ject performance, time, and cost; if there are discrepancies, (3) corrective actions are taken and the requirements, schedules, and budgets updated.Planning stepsFor starters, the project team needs to answer questions about what has to be done, how it has to be done, by whom, in what order, for how

4、 much, and by when. The formalized way to answer these questions is through the planning process.Project objectives, requirements, and scope are set;The specific work activities, tasks, or jobs to achieve objectives are broken down, defined, and listed;A project organization is created specifying th

5、e departments, subcontractors, and managers responsible for work activitiesA schedule is prepared showing the timing of work activities, deadlines, and milestones;A budget and resource plan is prepared showing the amount and timing of resources and expenditures for work activities and related items;

6、A forecast is prepared for time, cost, and performance projections for the completion of the project.Tools of Project Planning Work breakdown structure and work packagesused to define the project work and break it down into specific tasks.Responsibility matrixused to define project organization, key

7、 individuals, and their responsibilities.Events and milestonesused to identify critical points and major occurrences on the project schedule.Gantt Chartsused to display the project master schedule and detailed task schedules.Networksclearly show interdependencies among activities.Critical path analy

8、siscritical path gives the expected project duration.PERT/CPMprogram evaluation & review technology/critical path method Cost estimatingused to develop budgets and become the baseline against which project performance is evaluated. Budgetingan estimate may have to be refined many times, but once it

9、is approved, it becomes the budget. Forecastingplan is made before execution, so it has a nature of forecasting.二、计划的要求 目标是灵魂 符合实际 经济性要求 全面性要求 弹性要求 详细程度要求 相应的风险分析三、工程计划系统1、计划过程：持续的、循环的、渐近的过程 计划作为一个阶段，它位于项目批准之后，项目实施之前；而作为一个项目管理的职能工作，它贯穿于工程项目生命期的全过程。在项目过程中，计划有许多版本，随着项目的进展不断地细化、具体化，同时又不断地修改和调整，形成一个前后相继

10、的体系。2、工程项目计划的内容工期计划成本（投资）计划资源计划质量计划其他计划3、计划工作流程总工期计划项目定义、结构分解、组织结构设置实施方案劳动力使用计划网络计划资源使用计划其他费用计划成本计划支付计划收款计划资金计划符合实际分解落实否是4、计划中的协调 按照总目标、总任务和总体计划，起草招标文件、签订合同 投标人的计划纳入整个项目的计划之中 合同之间的协调 不同层次计划的协调 组织之间的协调四、工期计划1、工期计划过程 工期计划过程旨在确定工程活动的相关性及持续性，确保及时完成项目。它包括如下工作： 安排并确定项目活动间的逻辑关系 根据所需的资源、具体的条件，估计各项活动的持续时间； 按

11、总的进度目标编制详细的进度计划，形成网络，并进行网络分析。 工期计划是其他计划的基础。2、计划总工期的确定和分解 计划总工期作为项目的目标之一，对整个工期计划具有规定性。一般在目标设计阶段就被确定，并在可行性研究阶段被分解、细化、论证或修改。 总工期目标和主要阶段的工期安排可以通过： 分析过去同类或相似工程项目的实际工期资料，并根据本工程的特点推算； 采用工期定额(行业标准的滞后性；企业定额) 实际工程中，总工期目标通常从战略角度确定3、工程活动持续时间的确定 能量化的工程活动工程范围的确定及工程量的计算；劳动组合和资源投入量的确定；确定劳动效率；计算持续时间 非定量化的工作按过去工程的经验或

12、资料确定；与承担者协商确定 持续时间不能确定的情况Monte Carlo模拟；Delphi专家评议；三种时间的估计法 工程活动和持续时间均不确定滚动计划安排；加强对中间决策工作和决策点控制 横道图优点：清楚表达活动的开始时间、结束时间和持续时间；使用方便；可安排工期并与劳动力计划、资源计划和资金计划相结合。缺点：很难表达工程活动之间的逻辑关系；不能表示活动的重要性；所表达的信息量较少；不能用计算机处理。 4、工期计划方法Gantt ChartsThe simplest and most commonly used scheduling technique is the Gantt chart

13、(or bar chart), named after the famous management consultant Henry L. Gantt (1861-1919). The chart consists of a horizontal scale divided into time unitsdays, weeks, or monthsand a vertical scale showing project work elementstasks, activities, work packages, and so forth.Disadvantages of Gantt Chart

14、sOne disadvantage of the Gantt chart is that it does not explicitly show interrelationships among work elements, meaning that it does not reveal the effect of one work element falling behind schedule on other elements. In most projects, certain work elements must be completed by specific date to ens

15、ure that the project is completed on target; however, others can fall behind without delaying the project. 网络计划技术 是一种以网状图形表示计划或工程开展顺序的工作流程图。分单代号和双代号两种。132546ACEBDF213222双代号网络图6F23C15E32B24D2 7结束 0 0开始 01A2单代号网络图The two common methods for constructing network diagrams are called activity-on-node (AON

16、) and activity-on-arrow (AOA). Both were developed independently during the late 1950sAON as part of the CPM planning method, and AOA in the PERT method.Activity-on-arrow diagramsIn the AOA method, the activity is represented as a directed line segment (called an arrow or arc) between two nodes (or

17、circles). The nodes represent the start and finish events for the activity in between them. (The numbers inside the nodes have no significance here. In general, however, they are used to identify each event. The numbers do not need to be in any particular sequence, but every event must have a unique

18、 number.)ij“Start” event“Finish” eventDuration Activity YAOA representation for an activity and its start and finish events12345predecessor, immediate predecessor successor, immediate successorsequential activities, parallel activities dummy activities An AOA network is constructed by first drawing

19、a node to represent the origin event; this represents the start of the first activity in the project. The final or terminal node in the network represents the project completion. Every network should have only one origin event and one terminal event. All arrows must progress toward the right-end of

20、the network and there can be no doubling back or loops. Dummy activitiesA dummy activity is used to illustrate precedence relationships in AOA networks. It serves as a “connector”, however, and represents neither work nor time.In practice, dummy activities should be used sparingly to keep the networ

21、k as simple as possible.In constructing networks by hand, as a rule it is easiest to start by putting in dummy activities wherever they seem necessary, then removing them from places where they are not necessary. The “overriding rule” is that dummies cannot be removed whenever it results in two or m

22、ore activities that run between the same two start and finish nodes. Redundant activitiesAll activities in a project except the first one have predecessors. Although only the immediate predecessors need be known to construct a network, it is easy to accidentally specify more predecessors than necess

23、ary.ActivityPredecessorsRedundant PredecessorsImmediate PredecessorsA-BAACAADA, B, CAB, CEA, B, C, DA, B, CDFA, B, CAB, CThe critical pathThe major use of networks is for schedulingdetermining how long the project will take (the expected project duration) and when each activity should be scheduled.T

24、he expected project duration, Te, is determined by finding the longest path through the network. A “path” is any route comprised of one or more arrows (activities) connected in sequence. The longest path from the origin node to the terminal node is called the critical path; this gives the expected p

25、roject duration. Multiple critical pathsCan a project have more than one critical path? Why not? In the case of more than one critical path, a delay along any of these paths would extend the project duration. Suppose, you wanted to reduce the project duration; you would then have to shorten all the

26、paths. Early timesES and EFESs and EFs are computed by taking a “forward pass” through the network. When an activity has several immediate predecessors, its ES is the latest EF of all its immediate predecessors; this is the latest time when all the immediate predecessors will be completed and, hence

27、, the earliest time the next activity can be started. Late timesLS and LFBegin by assigning a target completion date, TS, to the terminal node, we make a “backward pass” through the network. Whenever an activity is encountered that has multiple paths leading back to it, it is the longest backward pa

28、th that becomes the basis for its LF. This is the same as saying that it is the backward path with the smallest LS that provides the basis for an activitys LF. Total SlackThe ES and LS for an activity are often not the same. The difference between LS and ES (or LF and EF) is referred to as the total

29、 slack time (or the “slack”, or the “float”) of an activity.Total slack=LS-ES(=LF-EF)Total slack for activities on the critical path (called critical activities) is zero; hence, delaying any of these activities will delay the project.Activities not on the critical path (called non-critical activitie

30、s) can be delayed by their slack time without delaying the project completion. Free SlackThe term free slack refers to the amount of time an activity can be delayed without affecting the start times of any successor activities. The free slack of an activity is the difference between EF for the activ

31、ity and the ES of its earliest successor:Free slack=ES(earliest successor)-EF Management schedule reserveThe Te first computed from the network is usually not the duration specified as the contractual completion time. A management schedule reserve is established by setting the required target time T

32、s at some amount greater than the time of the final scheduled event Te. Generally, the greater the uncertainty of the project, the larger the schedule reserve. Criticism of Network MethodsNetwork methods have been criticized since their inception because they incorporate assumptions and yield result

33、s that sometimes are unrealistic or prose problems to their users.Network methods assume that a project can be completely defined as a sequence of identifiable, independent activities with known precedence relationships. In many projects, however, the work cannot always be anticipated, and not all a

34、ctivities can be clearly defined. Rather, projects “evolve” as they progress.Also, it is difficult to demarcate one activity from the next, and the point of separation is more or less arbitrary. Sometimes successors can be started before predecessors are finished, so the two “overlap” in the sequenc

35、e. Although overlap of activities shortens the estimated project duration, the arbitrariness of demarcating the activities increases its variation. Precedence relationships are not always fixed, however, and the start of one activity may be contingent upon the outcome of an earlier one which may hav

36、e to be repeated. The result of a test activity, for example, may necessitate redoing analysis and design, which in a network is a “loop back” to activities that preceded the test.网络计划的基本原理首先 绘制工程施工网络图然后 通过计算指出关键工作好关键线路接着 选定目标不断改进计划,并对优化后的 方案付诸实施最后 在执行过程中进行有效的控制好监督双代号网络图的绘制示例施工过程ABCD紧前工作无ABB紧后工作BC.D

37、.E F.GF施工过程EFGH紧前工作BC.DC.EF.G紧后工作GHH无2A3B4C5D6EFG8H17关键工作和关键线路的确定若以网络终点节点的最早可能时间为网络总工期则关键线路上的各工作总时差皆为0若以合同工期为网络总工期,则以线路上总时差之和最小的线路为关键线路关键线路一般不止一条将关键线路的总时间缩短,关键线路可能变成非关键线路各类时差的相互关系Di-jDi-jDi-jFFi-jTFi-jIFi-jDFi-jTiETiLTjETjLPERT Three time estimatesPERT address uncertainty in the duration by using th

38、ree time estimatesoptimistic, most likely and pessimistic. These estimates then are used to calculate the “expected time” for an activity. The range between the estimates provides a measure of variability, which permits statistical inferences to be made about the likelihood of project events happeni

39、ng at particular times.The optimistic time is a minimum time activity could takethe situation where everything goes well; the most likely time is the normal time to complete the job; the pessimistic time is the maximum time an activity could takethe situation where bad luck is encountered at every s

40、tep.The pessimistic time includes likely internal problems but not environmental snags.The three estimates are related in the form of Beta probability distribution with parameters a and b at the end points, and m the modal, or most frequently, value. The PERT originators chose the Beta distribution

41、because it is unimodal, has finite end points, and is not necessarily symmetricalproperties that seem desirable for a distribution of activity times.035613Start of activityMost likely mOptimisticaAveragetePessimisticbActivity duration time t (days)Probability of tBased on this distribution, the mean

42、 or expected time te, and the variance, V, of each activity are computed using the following formulas:te=(a+4m+b)/6V=(b-a)/62The larger V, the less reliable te, and the higher the likelihood that the activity will be completed much earlier or much later than te. Probability of finishing by a target

43、completion dateBecause statistically the expected time of a sequence of independent activities is the sum of their individual expected times, the expected duration of the project, Te, is the sum of the expected activity times along the critical path:Te=teWhere te are expected times of the activities

44、 on the critical path.The variation in the project duration distribution is computed as the sum of the variances of the activity duration along the critical path:Vp=VWhere V are variances of the activities on the critical path.As examples, consider two questions about the project shown below:1) what

45、 is the probability of completing the project in 27 days?2) what is latest likely date by which the project will be completed?ij(a,m,b) te,VKey:17(6,15,30) 16,16.00834526(1,4,7) 4,1.00(3,4,5) 4,0.11(6,14,16) 13,2.78(4,11,12) 10,1.78(1,5,9) 5,1.78(1,2,3) 2,0.11(2,5,8) 5,1.00(3,12,21) 12,9.00(1,5,9) 5

46、,1.78(5,7,9) 7,0.44Path (events)T=teV=(b-a)/62a) 1-2-6-828*6.34b) 1-7-82017.00c) 1-2-5-7-829*6.00d) 1-4-5-7-8183.89e) 1-3-4-5-7-827*12.00* Critical path* “Near” critical pathBoth questions can be answered by determining the number of standard deviations that separate Ts from Te. The formula for the

47、calculation is:z =Ts-Te(Vp)1/2 Near-Critical pathsPutting too much emphasis on the critical path can lead managers to ignore other paths that are near-critical or have large variances, and which themselves could easily become critical and jeopardize the project.Because all activities in the network

48、must be completed before the project is finished, the probability of completing the project within 29 days is the same as the probability of completing all five paths within 29 days.The chance of completing all paths within 29 days is the product of the probabilities (1.01.0 0.67 0.72 0.5), which is

49、 less than 25 percent. Simulating a PERT networkMonte Carlo computer simulation is a procedure that takes into account the effects of near-critical paths becoming critical. Times for project activities are randomly selected from probability distributions and the critical path is computed from these

50、times. The procedure is repeated thousands of times to generate a distribution of project duration. The procedure gives an average project duration and standard deviation that is more realistic than simple PERT probabilistic analysis.Simulation allows the use of a variety of distribution besides Bet

51、a, including distributions based upon historical data. These generated project durations are more likely to represent the range of time to be expected. The method also avoids some limitations of PERT assumptions, such as independence of activities and normality of the project duration distribution.

52、Criticism of PERTPERT assumes that activity times can be accurately estimated and are independent. Getting three estimates instead of one adds to the work involved, and unless there is good historical data, all three are still guesses, which is not much of an improvement over a single “best” guess.I

53、f a “history” can be developed of similar activities from previous projects, activity time estimates can be improved. In fact, the requirement for good historical data upon which to base estimates makes PERT more appropriate for projects that are somewhat “repeatable”. For this reason the three time

54、 estimates are used primarily in construction and standardized engineering projects, but seldom elsewhere.The assumption of activity times independence also has been criticized. The duration of an activity is influenced whenever resources originally planned for it are transferred to other activities

55、 that need expediting.Two other criticisms of PERT are that it leads to overly optimistic results and that the Beta distribution gives large errors in estimating Te.Critical path method (CPM) Time-cost relationshipThe critical path method assumes that the estimated completion time for a project can

56、be shortened by applying additional resourceslabor, equipment, capitalto particular key activities. It assumes that the time to perform any project activity is variable, depending on the amount of effort or resources applied to it.Unless stated otherwise, any given activity is assumed to be performe

57、d at a normal work pace. Associated with this pace is the normal time, Tnhow long the activity will take under normal work conditions. Also associated with the normal pace is the normal cost, Cn, the price of doing the activity in the normal time. Usually the normal pace is assumed to be the most ef

58、ficient and thus least costly pace. Extending the activity beyond the normal pace will not produce any additional savings and might well increase the cost.To reduce the time to complete the activity, more resources are applied in the form of additional personnel and overtime. As more resources are a

59、pplied, the duration is shortened, but the cost rises. When the maximum effort is applied so that the activity can be completed in the shortest possible time, the activity is said to be crashed. The crash condition represents not only the shortest activity duration, but the greatest cost as well.The

60、 time-cost of completing an activity under normal conditions and crash conditions theoretically defines two extreme points. The line connecting these points, called the cost slope, represents the time-cost relationship, or marginal trade-off of cost-time for the activity.Assuming a simple linear rel