Project Management: Chapter3: Project Planning & Scheduling

Material Science: Chemical Bonding
August 23, 2017
Project Management: Chapter4: Project Monitoring & Control Process
August 29, 2017
  1. Project Planning Process

Steps in project planning are

Task involved in project planning

Functions of Project Planning

2. Work Breakdown Structure (WBS)

Advantages/Uses of WBS

Role of WBS

Levels of WBS

Characteristics of WBS

Criteria for developing WBS

A typical WBS of a project

3. Work breakdown of building construction

4. Scheduling Process

Necessity of scheduling

Scheduling techniques

5. BAR Chart (GANTT Chart)

Linked Bar Chart

Milestone Chart

Line of Balance Scheduling Technique

6. Schedule Network Analysis

Network Diagrams

Terminologies in network diagrams

Critical Path Method (CPM)

Project Evaluation and Review Technique (PERT)

Difference between CPM and PERT

Similarities between CPM / PERT

7. Resource Leveling

8. Resource Smoothing

Project Planning Process

  • It is concerned with the development of a project for investment.
  • It identifies and addresses the task required for accomplishment of objectives.

Steps in project planning are

Task involved in project planning are

Functions of Project Planning

  • Determining the objectives of the project to be undertaken.
  • Definition of work requirement.
  • Estimating resource, funds, materials, machines and manpower requirements.
  • Scheduling various stages and determining the time frame of overall work.
  • Reducing risk and uncertainty.
  • It provides the basis for co-coordinating the work among concerned; provide a basis for predicting & controlling time and cost.

Work Breakdown Structure (WBS)

Systematic and logical breakdown the project into its components and sub-components in hierarchical order is called work breakdown structure.

  • It is constructed by dividing a project into major components, each of which is further sub-divided into smaller components.
  • The process is continued till a breakdown accomplishes the manageable unit of works for which responsibility can be defined.

Work breakdown is the first and major step in planning and the execution of the project.

The level of smaller component should be such that each of which should be:

  • Manageable so that responsibility can be assigned.
  • Independent so that there is minimum dependence on other ongoing activities.
  • Integrable so that total package can be seen, and
  • Measurable so progress can be measured.

Advantages/Uses of WBS

Role of WBS

Levels of WBS

A most common six level structure of WBS is as shown below:

Characteristics of WBS

Criteria for developing WBS

A typical WBS of a project

Work breakdown structure of building construction

Scheduling Process

Scheduling is laying out of the actual jobs of the project in the time order in which they have to be performed.

  • Manpower and material requirements needed at each stage of construction are calculated, along with the expected completion time of each of the jobs.
  • A schedule shows the starting and completion dates of each activity and the sequential relationship among the various activities.

Necessity of scheduling

Scheduling necessity

To predict project completion time.

To control cost and resources.
To serve as record
 To manages changes and uncertainties.

 

Most commonly used tool for project scheduling are

  • Bar chart
  • CPM
  • PERT.

The project schedule is the tool that communicates

  • what work needs to be performed
  • which resources of the organization will perform the work and
  • the timeframes in which that work needs to be performed.

The project schedule should reflect all of the work associated with delivering the project on time. Without a full and complete schedule, the project manager will be unable to communicate the complete effort, in terms of cost and resources, necessary to deliver the project.

Techniques used for Scheduling

BAR Chart (GANTT Chart)

Properties:

  • This is a horizontal bar chart plotted over time (e.g. days, weeks or months).
  • Each activity is shown as a bar (its length based on a time estimate).
  • Depending on task dependencies and resource availability, these bars may be sequential, or run in parallel.
  • Each bar is plotted to start at the earlier possible start date.

History:

  • A bar chart is also called a Gantt chart since it was developed by Henry Gantt in 1920s.
  • It is one of the most popular and widely used techniques for planning and scheduling activities because the graphical representation of a bar chart makes it easy to read and understand.

The plan laid out when the GANTT Chart was created can be compared with actual times taken (plotted below the planned time bars in the chart).

  • Bar charts are useful and used to detect the amount of resources needed for one particular project.
  • Resource aggregation is done by adding resources vertically in the schedule.
  • The purpose of this aggregation is to estimate the work production and establishing estimates for man-hour and equipment needed

Advantages:

  • It is simple to understand.
  • Easy to prepare, consume less resources.
  • Easy to develop and implement, no training is required.
  • It can be used to show progress.
  • Appropriate for small projects.
  • Can be used for resources schedule.
  • It gives the clear pictorial model of the project.

Shortcomings:

  • Difficult to construct Bar chart for the large and complex project due to limitations of the size of paper.
  • The relationship between activities cannot be shown easily.
  • Difficult to find critical path, critical activities, and floats etc.
  • Difficulties in seeing immediately and exactly overall project duration if changes occur in any particular activity.
  • It cannot be used as control device
  • Long duration project may seem to be most important which may not be correct.
  • Difficult to manipulate and make corrections i.e. updating means to redraw the entire chart again.

Linked Bar Chart

  • A variation of the bar chart schedule.
  • A linked bar chart uses arrows and lines to tie the activities and subsequent items, specifying the successors and predecessors of every activity.
  • The previous activities are linked one to another to demonstrate that one activity must be completed before the other activity can start.

The linked bar chart has an advantage of exhibiting the effect of delay on succeeding activities and also it can provide some information of the extra time available (if there is) with an activity for its completion.

  • The extra time available for an activity for its completion is called float.
  • Similarly, the activities, which do not have extra time for completion, are called critical activities.

Milestone Chart

  • Milestone Chart is an improved version of a bar chart.
  • It is called Gantt Milestone Chart.

Combined activity bar charts can be converted to milestone bar charts by placing small triangles or circles or a flag at strategic locations in the bars to indicate completion of certain milestones within each activity or group of activities as shown in the figure below.

  • A milestone implies some specific stage or point where major activity either begins or ends, or cost data become critical.
  • Each bar in a milestone chart again represents an activity or job or task and all the bars took together represent the entire project.

How is it better than bar chart?

  • A milestone chart shows the relationship between the milestones within the same activity or job or task.
  • Thus as compared to the bar chart better control can be achieved with the help of a milestone chart

Shortcomings:

  • It does not depict the inter-dependencies between the various tasks or the relationship between the milestones of different tasks.

Line of Balance Scheduling Technique

  • It is a planning technique for repetitive work.
  • The essential procedure for this scheduling technique is to allocate the resources needed for each step or operation, so that the following activities are not delayed and the result can be obtained.

Applications:

  • The principles employed are taken from the planning and control of manufacturing processes
  • This process usually applied in the construction work and more specific in road construction.
  • It is very powerful and easy to use process when the conditions are ideal for this type of work.

Schedule Network Analysis

  • The schedule network is a graphical display (from left to right across a page) of all logical interrelationships between elements of work — in chronological order.
  • This order is from initial planning through to project closure.
  • As the project progresses, regular analysis of this network diagram is a check to ensure that the project is proceeding ‘on track’.

Network Diagrams

  • For a project involving a large number of activities, the project scheduling becomes very complex
  • The use of the conventional method of scheduling like bar charts will not be effective in such case.
  • Complex projects, if not correctly scheduled, will probably result in either under estimation or over estimation of the project implementation period.

Network diagrams are one of the modern tools of project management. There are two popular network based scheduling techniques.

  • Critical Path Method (CPM) 
    • Graphical network- based scheduling technique.
    • US Government agencies insisted on their use by contractors on major government projects.
  • Project Evaluation and Review Technique (PERT)
    • In 1958 US Navy developed project management tool known as PERT for scheduling Polaris Missile Project.

Following is an example network

Terminologies in network diagrams

Activity (Task):

  • An activity is any identifiable job which requires time, manpower, material and other resources to complete.
  • The arrow in a network diagram represents activity.

Concurrent (parallel) activities:

  • Which can be performed simultaneously and independently to each other.
  •  In the figure, A and B are concurrent activities.

Serial Activities:

  • Performed one after the other, in succession.
  • In the figure below A and B are serial activities.

Activity duration:

  • An activity’s duration is estimated the time required for its completion.
  • Time unit may be hours, days, weeks or months.

Activity duration= Work quantity/Production rate

Event (Node):

  • The beginning or end of the activity is known as event.
  • It represents specific time and does not consume time manpower, material, and other resources.

Two conventions can be used for developing networks are:

  • Activity on Arrow (AOA)
    • Here arcs represents activities of the project and nodes represents events
  • Activity on Node (AON)
    • Here the nodes represent activities, while arc(arrow) represent the precedent relations

Dummy Activity:

  • Which doesn’t consume resources like time, cost, manpower, equipment etc.
  • But is only used to show relationships.
  • It is represented by Dashed Arrow.

Dummies serve two purposes in network:

  • Grammatical purpose
    • It is used to prevent two arrows having the common beginning and end nodes for two or more activities.
  • Logical purpose:
    • Dummies are also used to give logical clear representation in the network having an activity common to two sets of operations running parallel to each other.

Earliest Start time (ES):

  • It is the earliest possible time an activity or operation can be started.
  • It is equal to the earliest occurrence time of the tail event of that activity.It is represented either EST or simply ESi

Earliest Finish Time (EF):

  • It is the earliest possible time for completion of an activity without delaying the project completion time.

EF= ES + duration

EFj=ESi+tij

Latest Finish Time (LF):

  • It is the latest time the activity must be completed without delaying project duration.
  • It is equal to the latest occurrence time of the head event.

Latest Start time (LS):

  • It is the latest possible time; an activity can be started without delaying the project.

LS= LF – duration

LSi=LFj – tij

Rules to draw Network diagram

Numbering the Events

Fulkerson’s Rule :

  • For any activity, the number on the Tail Event should not be greater than that on the Head Event.
  • In other words, the number on Head Event must always be greater than that on tail Event.

Critical Path Method (CPM)

Developed by Du-pont chemical works-USA in 1956/57 and used for preparing maintenance shutdown schedule of chemical plant for the first time.

Unlike bar chart, it uses arrows to represent activities and length of arrows has no relation with activity duration. Start or end of an activity is called event and it is shown by circles with the special designation.

Terminology:

  • Starting event is called tail event and ending event is called head event.
  • Some event plays dual both the role of head and tail such events are called dual role events.
  • Activity which must be completed before start of another activity is predecessor.
  • Activity which starts after completion of an activity is its successor.

  • Activity B is successor of activity A and activity A is predecessor of activity B.

Critical path:

  • The longest path in a CPM network is called critical path.
  • There may be more than one critical path in a network.

Project duration:

  • The time required to travel critical path is called project duration.

Critical activities:

  • The activities lying on critical path are called critical activities.

Floats

  • Float means the available free time for an activity, which is useful for managers to manage the limited resources.

An activity has four types of floats.

Total Float (TF):

  • It is the total free time for an activity i.e. maximum time by which completion of an activity can be delayed without affecting project completion time.

Significance:

  • It works as buffer time for managers, to meet contingencies like machine breakdown, labour absentism, etc.

 

TF= (LF-ES)-tij = ( LF-tij )- ES

                                                              = LS – ES

Example numerical:

Total float for this activity A-B is (LS – ES)  = (14 – 9) = 5

Free Float (FF):

  • It is the spare time allowable for an activity so that the start time of succeeding activities are not affected.
  • It is based on the possibility that all events occur at their earliest time.

FF = (EF -ES) – tij =EF – (ES+tij)

Numerical example:

Free float for the activity A-B is  = 20 – (9 + 10) = 20 – 19 = 1

Independent Float (IF or Ind. Float):

  • It is the maximum delay allowable for an activity so that the start time of succeeding activities are not affected.
  • It may come negative but should be taken as zero.

IF = EF – LS – tij

Numerical example:

Independent float for the activity A-B is  = 20 – (14 + 10) = 20 – 24 = -4 (considered as 0)

Interfering Float (Int. Float):

  • It is name given to head event slack. It is the difference between TF & FF.

Int. Float= TF – FF

Interfering float for the activity A-B is  = 5 – 4 = 1

CPM example:

There are three paths:

Paths Duration(weeks)
1-2-3-4 4+0+7=11
1-2-4 4+6=10
1-3-4 3+7=10

Hence from above definition,

  • Critical path= 1-2-3-4
  • Project duration= 11 weeks(time duration along the critical path)
  • Critical activities= 1,2,3,4

 

Event Duration (Weeks) Earliest Start Time Earliest Finish Time Latest Start Time Latest Finish Time Total Float
1-2 4 0 4 0 4 0
2-3 0 4 4 4 4 0
3-4 7 4 11 4 11 0
1-3 3 0 3 1 4 1
2-4 6 4 10 5 11 1

 

Characteristics of critical path:

It is the longest path of activities.
It determines the total project duration.
There may be more than one Critical Path in a network.
A Critical Path may consist of less no. of activities than Non-critical Path.
The Critical Activities demand the requirement of resources prior to other activities to complete the project in time.

Significance of critical path:

  • If there is any delay in either starting or if the time taken to complete critical activity exceeds the estimated time, project implementation period will get extended.
  • Thus, any delay in critical activities leads to time overrun of the project which ultimately results in cost overrun.

Advantages of Critical Path Method

  • Makes dependencies visible.
  • Organizes large and complex project.
  • Enables the calculation of float of each activity.
  • Encourages the project manager to reduce project duration.
  • Increases visibility of the impact of schedule revisions.
  • Provides opportunities to respond to the negative risk going over-schedule.

Shortcomings

  • In large and complex projects, there will be thousands of activities and dependency relationships.
  • This method doesn’t account for resource and resource allocation.

Project Evaluation and Review Technique (PERT)

Like CPM, PERT is also a network based planning tool developed by US Navy in 1958. It was used for scheduling Polaris Missile Project.

  • But, unlike CPM, PERT is used for novel projects like research and development (R & D) where it is difficult to estimate activity duration accurately.
  • CPM is used for projects with prior experience such as civil engineering works.
  • It is a probabilistic approach for estimating project duration of an activity and event-oriented network diagram.
  • PERT is preferred for those projects in which correct time determination for various activities cannot be made.

PERT uses three-time estimate for each activity with a view to overcoming uncertainty in time estimates.

Optimistic time estimate (t0):

  • It is minimum time i.e. the shortest possible time required to complete the activity in ideal conditions.

Pessimistic time estimate (tp):

  • Maximum time required to complete the activity in the worst condition.

Most probable time estimate (tm):

  • Time required to complete the activity in normal circumstances.

From these three time estimates, we calculate average time i.e. expected time (te) using the following formula.

te=(t0+4 tm+tp)/6

PERT assumes optimistic time and pessimistic time are equally likely to occur while the most likely time is four times more likely to occur than the other.

Similarly, standard deviation (σ) is calculated using,

S.D. (σ) = (tp-t0)/6           and

Variance (σ2) = [(tp-t0)/6]2

Difference between CPM and PERT

 CPM  PERT
 Deterministic tool, with only single estimate of duration  Probabilistic tool used with three estimates of duration
 Activity oriented  Event oriented
 CPM considers less uncertainty  PERT considers more uncertainty
 Suited for routine projects         requiring accurate time and cost estimates  Suitable for R&D related projects where the project is performed for the first time and the estimate of duration are uncertain
 CPM can control both time and cost This tool is basically a tool for planning and control of time
 Easy to maintain  Costly to maintain

Similarities between CPM / PERT

  • Both tools lead to the same end:
    • A Critical Path and Critical Activities with the slack time equal to zero.
  • Extensions of both PERT and CPM allow the user to manage other resources in addition to time and money, to trade off resources, to analyze different types of schedules, and to balance the use of resources.

Project Scheduling with Limited Resources/Resource Allocation:

Planning is usually done for unlimited and readily available resources.

However, in practice, resources are usually limited and scarce. There are many jobs sharing common resources and available resources are not adequate enough.

But, the beauty of the scarce resources is that they can be managed.

  • To finish a construction project at maximum efficiency of time and budget it requires the sound planning of schedule and allocation of available resources.
  • Resources like man power, materials and equipment are of great importance and requires close attention.

The seasonal shortage, labor disputes, equipment breakdowns, competing demands, delayed deliveries and many other uncertainties affect supply and availability of resources so, this is seldom be taken for granted.

Most project managers problems:

  • Relatively fixed manpower, a certain number of machines or equipment, and a limited budget.
  • Jobs that occur on parallel paths through the network or concurrent activities may require the same resources, and even though precedence constraints would not prevent their being scheduled simultaneously, a limited supply of resources might force them to be scheduled sequentially.
  • Lack of adequate resources may lead to the revision of established schedules.

If the resources demand exceeds the supply, remedial measures to combat inadequate resource supply is to be made. If there are conflicts among project activities for the same resource items, activity duration & precedence relationships should be considered and rescheduling the non- critical activities will often solve the problem.

In most project situations resources can be acquired or released in practically any desired amounts if one is willing to pay expenses involved in changing resource levels, such as the costs of hiring, training, unemployment insurance, and so on.

It is usually prudent, however, to maintain relatively stable employment levels and to utilize resources at a more constant rate.

The scheduler may use activity slack as a means of smoothing peak resource requirements.

Resource Leveling

It is the method of scheduling activities within their available float so as to minimize fluctuations in a day- to- day resource requirements. It is done by moving project activities.

Resource leveling is necessary to:

  • Implement the project effectively.
  • To reduce the cost of a project.

By resource leveling

  • we try to optimize the use of resources required to complete a project.
  • Resource leveling helps in obtaining uniformity (as far as possible) in resource requirement throughout the life of a project.
  • It will ease resource management so that cost involved in managing resources can be minimized.

If resource is manpower, its leveling is called Manpower Leveling

  • Like manpower, Materials schedule is also done based on CPM/PERT analysis.
  • It helps to deliver materials at the site well in advance but avoids delivery far in advance, as a result of which deterioration, damages etc. are avoided.

Resource Smoothing

Resource smoothing is part of resource leveling process. It is defined as a technique that adjusts the activities of a schedule model such that the requirements for resources on the project do not exceed certain predefined resource limits.

  • In itself, attempts to determine resource requirement that is “smooth” and where peaks and troughs are eliminated.
  • Even if there is no limit to the amount of any resource available, it is desirable that resource usage is as smooth as possible.

References

CPM: https://www.kullabs.com/classes/subjects/units/lessons/notes/note-detail/5480

PERT: https://www.kullabs.com/classes/subjects/units/lessons/notes/note-detail/5494

Scheduling with BAR Chart (GANTT Chart) https://www.kullabs.com/classes/subjects/units/lessons/notes/note-detail/5323

 

5 Comments

  1. Rahul says:

    I think definition of independent float is wrong.
    It should be preceding activity instead of succeeding

  2. anand says:

    Even the Smoothing and leveling explanations are wrong( exchanged ).

  3. Patrick Maina says:

    What are the techniques used in planning and scheduling the different tasks in health project management

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