Chapter 1 INTRODUCTION

Transcription

1 Chapter 1 INTRODUCTION

2 Plans (blueprints) Planning what how where who. Scheduling To determine "when."

3 Plans (blueprints) The "plans" (blueprints) and specifications for the project generally define both the end product and the general time frame However, they normally do not specifically identify the individual steps, their order, and the timing followed to achieve the end product.

4 Scheduling A timetable of activities, such as of "what will be done or "who" will be working. Such a timetable can be looked at in two ways the first is focusing on an activity, such as determining "when" a certain task will be performed The second is concentrating on a specified time frame and then ascertaining "who" will be working (or needed) or "what" should be occurring at a particular time

5 Planning Planning relates to developing the logic of how a project will be constructed, while scheduling consists of integrating that plan with a calendar or a specific time frame.

6 The Widespread use of bar charts Easily to be understood with only a cursory examination. the activity sequencing can surmise easily when each activity is to begin and when it is to be completed. This simple example shows at a glance how the different activities relate to each other. With the time-scale presentation, a bar chart shows operations and the time consumed by each operation. In addition, it can show the scheduled versus actual progress.

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8 Dark shaded activities are critical as they must occur as scheduled or the project duration will be adversely impacted. Light shaded activities are not critical as they can be delayed at least one day without having an adverse impact on the project duration. The /1>/1 symbols designate days that an activity duration could be extended, commonly known as free float.

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10 Network modeling techniques There are actually two similar network modeling techniques : the Critical Path Method (CPM) it is important to recognize the distinction between duration and event. Program Evaluation and Review Technique (PERT).

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12 CPM (the critical paths) Identify those chains of activities (the critical paths) in the project that control how long the project will take. Activity-an-Arrow (A-on-A), or an arrow diagram, because activities are represented in the network as arrows or lines. Activity-an-Node (A-on-N) more commonly referred to as the Precedence technique. This method defines the activities as boxes (nodes in the network)

13 Example Network system B 15 C 5 E 21 A 90 F 25 G 14 D 20 H 28 I 30 J 45

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15 the matrix schedule

16 Chapter 2

17 The fundamental concept of a network-based planning and scheduling tool is that the network represents a time-oriented model of a system, not unlike a physical scale model of a project. The associations of the various tasks required to construct a project must be fully understood and these relationships must then be clearly conveyed to the user in the final network

18 1. Define activities 2. Order activities 3. Establish activity relationships and draw a network diagram 4. Determine quantities and assign durations to activities 5. Assign resources and costs 6. Calculate early and late start/finish times 7. Compute float values and identify the critical path 8. Schedule activity start/finish times

19 These activities use traditional resources of labor and materials. Another one is time, as the curing of concrete may be a viable activity to be included in the network.

20 These activities include arranging for the acquisition of materials, money, equipment, and manpower. These may include a number of activities that influence the timing of production activities. Special-order, long, or uncertain lead-time item should always have procurement activities incorporated into the network

21 The scheduler should always be aware of those required "extra" or management activities that are not included in the above two categories. As preparing inspection reports, processing shop drawing approvals, tracking submittal approvals, developing as-built drawings, providing certifications on factory tests performed, and a variety of similar tasks may need to be included.

22 For each identified activity, the following must be determined: Which activities must precede it? Which activities must follow it? Which activities can be concurrent with it?

23 Physical Constraints Resource Constraints Safety Constraints Financial Constraints Environmental Constraints Management Constraints Contractual Constraints Regulatory Constraints

24 Reduce scheduling flexibility Lengthen project duration Generally increase project cost Confuse basic scheduling logic

25 Only physical constraints should be entered during the early development stage of the project model. Once the basic network is completed, the constraints should be imposed in some sequence. When the impact of a particular constraint is especially severe, the scheduler will probably reassess the need for the particular constraint.

26 IPAs : immediate preceding activities

27 Most popular software that is currently used for computer scheduling supports only precedence diagrams. For some inherent disadvantages of arrow diagrams, arrow diagrams are no longer used extensively in the construction industry. Precedence diagrams and arrow diagrams present the same basic information about the sequence of activities that must take place to complete a project.

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29 the unit of time is days and it is assumed that work is performed on a continuous and uniform basis within the standard workday and work week. Activity durations frequently are tied directly to the resources applied to them (e.g., crew size and equipment) and the productivity of these resources durations always are directly related to labor cost estimates for the tasks.

30 Chapter 3

31 Nodes: These represent "Activities" and may be drawn in any shape desired. Often they are drawn as circles, boxes, or other common geometric shapes Lines: Lines represent "Activity links," which are used to represent the dependencies between activities.

32 ACTIVITY RELATIONSHIPS In the past, relationships between activities were defined as being finish-to-start (FS),whereby the preceding activity must be finished before the succeeding activity can start. Other types of relationships are also encountered, namely start- to-start (SS), finish- to-finish (FF), and start- to-finish (SF).

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34 The activity "Cure concrete" is typically one that does not entail the use of resources, other than time itself. The activity "Cure concrete" is simply a means of putting a delay activity between placing the concrete and stripping the forms. These activities (placing concrete and stripping forms) might also be shown as being related by finish-to-start with a delay.

35 Finish-to-Start (FS)

36 Sequence of Finish-to-Finish with a Delay Relationship

37 Activities with Start-to-Start

38 ACTIVITY RELATIONSHIPS

39 ACTIVITY RELATIONSHIPS

40 S-S and F-F S-S F-F F-F S-S F-S

41 Determining Activity Durations

42 The development and use of schedules relies heavily on activity durations. Without carefully assigning durations to the various activities, the value of the schedules will be greatly diminished. The accuracy and usefulness of the schedule will be directly related to the accuracy that is inherent in the individual activity durations.

43 ESTIMATING the estimator should have an accurate estimate of the quantities of material, equipment hours, and labor hours required to complete a given project. The soundness of the completed estimate depends on the following factors: (1) the accuracy of the quantity take-off (2) the judicious selection of the unit costs and production rates to be used.

44 TYPES OF ESTIMATES Conceptual estimates Detailed estimates

45 Conceptual estimates To determine the approximate cost of a project before making a final decision Approximations of the anticipated costs Prepared by architects, engineers, or other consultants. requires a clear understanding of what an owner wants and a good "feel" for the probable costs.

46 Detailed estimates prepared by contractors prior to submitting bids on competitively bid contracts or when entering lumpsum or fixed-price contracts. the direct costs: materials, labor, equipment, subcontracted works the indirect costs: overhead, and profit.

47 CONDUCTING A DETAILED ESTIMATE Costs are generally captured Materials equipment, labor, subcontracted items. the take-offs, in general, follow the same sequence as used to perform the activities.

48 Unit price contracts Unit price contracts may include work that must be done but for which there is no specific quantity pay item. For example, extensive scaffolding may be required to construct a project, but the owner will probably not allow scaffolding to be used as a pay item.

49 新產品 [0] [ 工期 = 766 天 ] 新產品開發範本 [1] [ 工期 = 766 天 ] 初期新產品審查階段 [1.1] [ 工期 = 9 天 ] 試驗階段 [1.4] [ 工期 = 115 天 ] 商業化階段 [1.5] [ 工期 = 195 天 ] 公告商業化檢閱結果 [1.6] [ 工期 = 130 天 ] 開發階段 [1.3] [ 工期 = 264 天 ] 初步調查階段 [1.2] [ 工期 = 53 天 ] 描述新產品概念 ( 單頁書面討論 ) [1.1.2] [ 工期 = 2 天 ] 搜集進行 / 不進行決策所需的資訊 [1.1.3] [ 工期 = 6 天 ] 召集審查委員會的機會 ( 決定是否貫徹概念 ) [1.1.4] [ 工期 = 1 天 ] 指示新產品機會 [1.1.1] [ 工期 = 0 天 ] 試驗分析 [1.4.4] [ 工期 = 49 天 ] 保全客戶保證以加入商業化試驗 [1.4.2] [ 工期 = 5 天 ] 指派試驗階段資源 [1.4.1] [ 工期 = 1 天 ] 試驗產品製造 [1.4.3] [ 工期 = 70 天 ] 產品製造及監控 [1.5.1] [ 工期 = 168 天 ] 商業化分析 [1.5.2] [ 工期 = 57 天 ] 決定產品是否能夠禁得起市場競爭 [1.6.3] [ 工期 = 30 天 ] 決定目前的經濟效益是否與所規劃的經濟效益一致 [1.6.5] [ 工期 = 15 天 ] 決定銷售是否符合計劃 [1.6.2] [ 工期 = 60 天 ] 評估機會以決定是否擴展產品或產品生產線 [1.6.6] [ 工期 = 15 天 ] 決策點 - 進行 / 不進行試驗階段 [1.3.6] [ 工期 = 0 天 ] 概念評估 [1.3.4] [ 工期 = 57 天 ] 市場評估 [1.3.2] [ 工期 = 40 天 ] 技術產品評估 [1.3.3] [ 工期 = 204 天 ] 開發初步調查計劃 [1.2.2] [ 工期 = 5 天 ] 指派初步調查的資源 [1.2.1] [ 工期 = 1 天 ] 技術可能性分析 [1.2.5] [ 工期 = 20 天 ] 起草初期開發階段計劃 [1.2.12] [ 工期 = 10 天 ] 決定環境問題 [1.2.8] [ 工期 = 10 天 ] 開發風險分析 [1.2.11] [ 工期 = 5 天 ] 檢閱法律問題 [1.2.9] [ 工期 = 10 天 ] 分析競爭性 [1.2.4] [ 工期 = 5 天 ] 決定點 - 進行 / 不進行初步調查 [1.1.5] [ 工期 = 0 天 ] 決定產品是否符合客戶成本 / 效能期望 [1.6.1] [ 工期 = 60 天 ] 指派開發階段計劃的資源 [1.3.1] [ 工期 = 1 天 ] 指導初步檢閱決策 [1.2.13] [ 工期 = 2 天 ] 決定安全性問題 [1.2.7] [ 工期 = 10 天 ] 基於穩定性及成本效益評估製造流程 [1.6.4] [ 工期 = 40 天 ] 指導開發階段檢閱 [1.3.5] [ 工期 = 2 天 ] 評估市場 [1.2.3] [ 工期 = 10 天 ] 評定製造可能性 [1.2.6] [ 工期 = 10 天 ] 執行財務評估 [1.2.10] [ 工期 = 10 天 ] 決策點 - 進行 / 不進行開發階段 [1.2.14] [ 工期 = 0 天 ]

50 the estimator may develop the productivity rates by discussing relevant factors with superintendents, project managers, and other experienced personnel. The estimator may also decide to obtain rough values of productivity from published sources. Whenever reference is made to another source for production values, the estimator should take care to make appropriate modifications to reflect the anticipated conditions.

51 The jobsite and the home office overhead The job site overhead includes all of those costs that cannot be attributed to a specific work activity, but that must be incurred to successfully complete the project. As the cost of maintaining a job pickup truck, the salary of the superintendent, and the cost of an electric generator.

52 Chapter 5 Time in Contract Provisions

53 TIME IS OF THE ESSENCE Time shall be strictly of the essence of the contract. The Contractor shall promptly begin the work under the contract and all portions of the project made the subject of the contract shall be begun and so prosecuted with necessary plant, equipment, procedures, and overtime that they shall be completed and ready for full use in the time stated in the special conditions.

54 REQUIREMENTS FOR PROJECT COORDINATION Within ten days following award of the contract, a preconstruction conference will be held in the Owner's office. The Contractor shall be represented at the meeting by the job superintendent or foreman. All aspects of the job will be discussed and representatives of various agencies with interest in the project will be present to answer questions.

55 Preconstruction Conference A progress schedule showing the order in which the Contractor proposes to carry out the work and the contemplated dates on which the Contractor and any Subcontractors will start and finish each of the salient features of the work, including 1. any scheduled period of shutdown. 2. The schedule shall also indicate any anticipated periods of multiple-shift work. A list showing anticipated dates for procurement of materials and equipment, the ordering of articles of special manufacture, the furnishing of plans, drawings, and other data required under this contract and for any other events such as inspection of structural steel fabrication.

56 Cooperation The Owner, or contractors on be half of the Owner, shall be at liberty to enter upon the site of the work with workers and materials to do work the Contractor shall afford any such workers all reasonable facilities and cooperation to the satisfaction of the Owner's Representative. Any conflict arising between the on Contractor and any other contractor employed by the Owner, or between the Contractor and the workers of the Owner with regard to their work, shall be submitted to the Owner s Representative for a decision on the matter. If the work of the Contractor is delayed because of any acts or omissions of any other contractor or of the Owner, the Contractor may claim for extensions of time and/or compensation in accordance with the contract.

57 PROGRESS SCHEDULE The delivery date for owners want to make about project completion dates, so they often independently monitor projects to evaluate adherence with the schedule. A reasonably reliable schedule is to monitor the project with a schedule to which both the owner and the contractor have agreed. In some cases owners prepare the schedules and have the contractors make suggestions for modifications. It is more typical for the contractor to prepare the schedule for the owner s approval. The requirements for the project schedule may vary considerably from project to project or from owner to owner.

58 PROGRESS SCHEDULE For the special provisions, the Contractor shall submit to the Owner's Representative a practicable progress schedule within 20 working days of approval of the contract, and within ten working days of Owner's Representative's written request at any other time. the Contractor may be requested, on or before the last day of each month, to indicate the status of work actually completed during the preceding estimate period.

59 PROGRESS SCHEDULE The schedule shall show the order in which the Contractor proposes to carry out the work, and the contemplated dates for completing the said salient features. The progress schedule submitted shall be consistent in all respects with the time and order of work requirements of the contract. No payments will be made for any work until a satisfactory schedule has been submitted to the Owner's Representative.

60 PROGRESS SCHEDULE After the award of the contract and prior to starting work, the Contractor shall submit to the Owner's Representative a satisfactory progress schedule or critical path schedule(cpm) which shall show the proposed sequence of work, and how the Contractor proposes to complete the various items of work within the number of working days set up in the contract or on or before the completion date specified in the contract.

61 PROGRESS SCHEDULE This schedule shall be used as a basis for establishing the controlling item of construction operations and for checking the progress of the work. The controlling item shall be defined as the item which must be completed either partially or completely to permit continuation of progress. It shall be the responsibility of the Contractor to show the intended rate of production for each controlling item listed on the schedule during the period such item is controlling.

62 PROGRESS SCHEDULE The Contractor shall confer with the Owner's Representative at regular intervals in regard to the prosecution of the work in accordance with the progress schedule or critical path schedule.

63 PROGRESS SCHEDULE The Contractor shall submit a progress schedule on an approved form within 15 days after the execution of the contract showing how the work is to be prosecuted. If the Contractor s operations are materially affected by changes in the plan or in the amount of the work or if there is a failure to comply with the approved schedule, the Contractor shall submit a revised progress schedule, if requested by the Owner's Representative, which schedule shall show how the balance of the work is to be prosecuted.

64 PROGRESS SCHEDULE The Contractor shall incorporate into every progress schedule submitted, any contract requirements regarding the order of performance of each portion of the work. All practicable means shall be used to make the progress of he work conform to that shown on the progress schedule that is in effect. No payment will be made to the Contractor while delinquent in the submission of a progress schedule. Should the prosecution of the work, for any reason, be discontinued, the Contractor shall notify the Owner's Representative at least 24 hours in advance of resuming operations.

65 The schedule Content After Notice of Award (a) all activities that have a duration of four weeks or longer (b) dates of order and delivery of all major items of equipment and/or material (c) milestone dates (d) restraints (e) interfaces with other contractors or subcontractors, (f) proposed weighted values for each category of work, reflecting that category as a percentage of the total scope of work.