Critical Path Method in Project Management

                           
                           
                             WELCOME
                             WELCOME
                                     
                                     
TO
TO
                              LECTURE 6
                              LECTURE 6
                   
                   
SELESTIAN AUGUSTINO
SELESTIAN AUGUSTINO
Try this question now:  Draw a network diagram
    3.1.11 Critical Path Method ES, EF, LS, LF, FLOATS
    3.1.11 Critical Path Method ES, EF, LS, LF, FLOATS
Early Start-ES
Early Start
 or 
ES
 is the earliest time that activity can start. An activity
near the end of path or much later will only start if all the previous
activities in the path also started early. If any one of the previous
activities slips then it will push this activity out.
Early
 Finish-EF
Early Finish
 or 
EF
 is the earliest time that activity can finish. It is the
date that an activity can finish if all previous activities started early and
none of the activities slipped.
If project manager and team knows about early start and early finish
dates of all the activities(tasks) then they will know how much freedom
they have to move the start dates without causing any problem to the
project.
Tips for calculation of ES, EF during forward pass
Forward pass is the direction from left to right as you traverse on network
diagram.
 ES of first activity = 1
 ES of all other activities = EF(of previous activity) + 1
 If two activities say A and B converge (i.e. merge) to one activity, say C
in forward pass, then ES of activity C = (greater EF from activity A and B)
+ 1
 EF = ES + duration -1
                          Sample diagram
Late Start-LS
Late Start
 or 
LS
 is the latest time an activity can start. If an activity is
on the path which is much shorter compare to critical path, then it can
start much late without any delay to the project.
Late Finish-LF
Late Finish
 or 
LF
 is the latest time that an activity can finish.
If an activity is on a shorter path and all of the other activities on same
path start as well as finish early, then it can finish very late without
causing project to be late.
Knowing late start and late finish will help you see how much it can
be played around in the schedule. If an activity has large LS and LF
means there are more options available.
Tips for calculation of LS, LF during reverse pass
Reverse/Backward pass is the direction from right to left as you
traverse on network diagram.
 LF of last activity = EF of the same last activity
 For all other activities except the convergence mentioned in the next
line, LF = LS(of previous activity) -1
 If two activities say A and B converge (i.e. merge) to one activity in
the reverse pass say C then, LF(of activity C) = (Lesser LS from
activity A and B) -1
 LS = LF - duration +1
                         Sample diagram
Problem 3: 
The following data are available for construction project. a)
Construct a network diagram  b) Calculate the project completion time  c)
Find the critical path and critical activities  d) Determine the ES, EF, LS,
LF and TF of each activity
Floats
Float
 / 
Slack
 is the amount of time an activity or project can be delayed from the
early start without changing the completion date of the project.
Types of float
Types of float
                              1.Total Float (TF)
The amount of time that an activity can be delayed or extended from its early start
date without delaying the 
project finish date
 or 
violating a schedule constraint
.
Mathematically: Late Finish – Early Finish = Total Float
Mathematically: Late Finish – Early Finish = Total Float
                             2. Free Float (FF)
The amount of time that an activity can be delayed without delaying the 
early start
date of any successor
 or 
violating a schedule constraint
.
Mathematically: Earliest Successors’ Early Start – Activity’s Early Finish = Free
Mathematically: Earliest Successors’ Early Start – Activity’s Early Finish = Free
Float
Float
                                  Floats
                   3.  Interfering Float (INTF)
The amount of time that an activity can be delayed or extended from its early start
date without delaying the 
project finish date
, but delaying an activity into interfering
float will delay the start of one or more following non-critical activities. If an
activity is delayed for the amount of the Free and Interfering Float, its successor
activities are critical.
Mathematically: Total Float – Free Float = Interfering Float
Mathematically: Total Float – Free Float = Interfering Float
                   4.  Independent Float (INDF)
The maximum amount of time an activity can be delayed without delaying the 
early
start of the succeeding activities
 and 
without being affected by the allowable delay
of any predecessor activity.
Mathematically: Predecessors’ Late Finish – Activity’s duration = Independent
Mathematically: Predecessors’ Late Finish – Activity’s duration = Independent
Float
Float
Remark
: when the result is a negative value, we set the value to zero.
                                 
Advantages of CPM
The CPM makes it easier for the project managers to build a team and create
human network for efficient handling of a multi-tasked project.
The Critical Path Method binds the entire team together and motivates the human
resources in timely completion of the tasks in a project.
 The CPM takes into consideration the requirements well in advance to complete a
project in the most efficient way possible.
With help of the Critical Path Method the project managers can determine the
duration and estimate exact time and cost of the project. It helps to monitor human
resources, and the direct and indirect costs associated with the project.
The CPM assists the project managers in planning schedules, monitoring tasks,
and helps control the project expenses.
The Critical Path Method also makes it convenient for the project managers to
calculate the time required to complete the tasks of the project. That helps them to
predict completion date of every phase, anticipate problems along the way, if any,
and react accordingly.
                            
Disadvantages of CPM
In a big project, a CPM can become extremely complicated and difficult to fathom
for the new recruits to the project team.
If the project is far too bulky and lengthy, the Critical Path Method requires
software to monitor the plan.
CPM can become ineffective and difficult to manage if it is not well-defined and
stable.
It cannot effectively handle sudden changes in the implementation of the plan on
ground. It is very difficult to redraw the entire CPM chart if the plan of the project
suddenly changes midway.
The Critical Path Method cannot form and control the schedules of the persons
involved in the project.
The allocation of resources cannot be properly monitored.
The critical path of the CPM of a big project is not always clear. The project
managers have to spend a lot of time to calculate it carefully.
The Critical Path Method takes longer to identity and to monitor the critical path
when the project is of big dimension
.
Using CPM, identifying and determining a critical path is difficult when
there are many other similar duration paths in the project.
At times, to design a CPM is time consuming. It is also difficult to estimate
the activity completion time in a multidimensional project.
                     Self study
                     Self study
1.  Enumerate the concrete significance of CPM (At least 4 points).
 
3.1.12 Time Estimation in PERT (With Calculation)
There are three different estimates of activity duration in PERT:
1. Optimistic time 2. Pessimistic time 3. Most Likely time
1. Optimistic time 2. Pessimistic time 3. Most Likely time
1. Optimistic time
1. Optimistic time
, expressed as ‘
t
o
‘, represents estimate of minimum
possible time by which an activity can be completed assuming that
everything is in order according to the plan and there can be only
minimum amount of difficulty.
2. Pessimistic time
2. Pessimistic time
, expressed as ‘
t
p
’ represents estimate of maximum
possible time by which an activity can be completed assuming that
things may not be in accordance with the plan and there can be
incidence of difficulties in carrying out the activity.
3. Most Likely time
3. Most Likely time
, expressed as ‘
t
m
‘, represents estimate of time for
completion of an activity, which is neither optimistic nor pessimistic,
assuming that things should go in a normal way, and if the activity is
repeated several times, in most of the cases, it will be completed in
time represented by 
t
.
From the above three different time estimates, PERT suggests to work out the
following;
 
The expected time, expressed as (
The expected time, expressed as (
t
t
e
e
) which is the average of  
) which is the average of  
t
t
o
o
 , t
 , t
p
p
 and
 and
t
t
m
m
 calculated as,
 calculated as,
                               t
                               t
e
e
= (t
= (t
o
o
 + 4t
 + 4t
m
m
 + t
 + t
p
p
 
) / 6
) / 6
                                                      
The variance expressed as (Var.) , calculated as,
The variance expressed as (Var.) , calculated as,
                             Var.= ((
                             Var.= ((
t
t
p
p
 -
 -
t
t
o
o
)/6)²
)/6)²
The standard deviation expressed as 
The standard deviation expressed as 
σ 
σ 
,which is the square root of
,which is the square root of
variance (Var.) calculated as,
variance (Var.) calculated as,
                              
 
 
σ
σ
 = √(Var.) = √((
 = √(Var.) = √((
t
t
p
p
 -
 -
t
t
o
o
)/6)²= (
)/6)²= (
t
t
p
p
 -
 -
t
t
o
o
)/6
)/6
         
Problem 4: 
Using the tabulated schedules below,
a)
Draw the PERT network diagram
b)
Calculate the expected time, variance and  standard
deviation of each activity
c)
Draw the CPM network diagram
d)
Calculate the project completion time
e)
Find the critical path
f)
Identify the critical activities
Table 1
Table 2
                             Difference between PERT and CPM
Self study
Self study
1.
What are the advantages and disadvantages of PERT?
What are the advantages and disadvantages of PERT?
(At least 5 points @)
(At least 5 points @)
      3.2.0 Resource Management
      3.2.0 Resource Management
Resource
 is a stock or supply of money, materials, staff, and other assets that can be
drawn on by a person or organization in order to function effectively.
Resource management 
is the process of planning, scheduling, and allocating
resources in the best possible way.
 
The ultimate aim is to maximize the resources’
efficiency. This means, it ensures that internal and external resources are used
effectively on time and to budget.
                                                     
OR
OR
Resource management 
is the process of planning the resources necessary to meet the
objectives of the project, and to satisfy the client’s requirements.
                                                    
OR
OR
Resource management
 is the efficient and effective development of an
organization's resources when they are needed.
Example: Financial resources, inventory, human skills, production resources, or
information technology (IT) and natural resources.
                                                    
OR
OR
Resource management
 is acquiring, allocating and managing the resources, such as
individuals and their skills, finances, technology, materials, machinery and
natural resources required for a project.
       3.2.1 Need for resource management
   
Resource management is needed because:
It provides the overview of everyone and everything involved in the
project
It enables utilization planning
It makes the planning and management process more transparent
It help you to see problems before they start
It gives control over the project
Techniques used in resource management are:
                                1.   Resource Levelling
                                1.   Resource Levelling
                                2.   Resource Allocation
                                3.   Resource Forecasting
   
 3.2.2 Basic important types of resources in
construction projects
                                   1.    Human resource
                                   2.    Financial resource
                                   3.    Material resource
                                   4.    Machinery resource
1. Human resource
1. Human resource
No matter the size and complexity of the project, in order for the project
tasks to be performed effectively, human resources are essential.
Human resources are considered to have the most complex requirements
than the other two types of project resources. Therefore, project managers
should plan in advance and identify potential people to become part of the
project team by making sure they are available and skilled for the project in
question.
Normally a project team is a group of people that is managed by a project
manager. The team management part is often the hardest part of the project,
especially if the manager hasn’t had to lead a team in the past.
Managing the project team’s time and workload can be tricky too, as,
usually, most of the project team members don’t work solely on one project.
They often have day jobs and may be involved in other projects at the same
time.
                                    1. 
                                    1. 
Human resource
Human resource
If you, as a project manager, know what individuals you need for your
project it could be a lot easier to do your resource planning, which
should help you balance those peaks and troughs of availability in the
team. Spend some time thinking through the different skill sets that you
need and the kind of tasks that are required for the project, regardless of
the project complexity and type.
Even at this early stage, you can still get a good idea of who needs to be
involved. You’ll have to work out who is needed on the project at what
times, based on your project schedule. You’ll need to bring in different
types of subject matter experts at different times, and each one will
have to know enough about the project’s objectives to get their part
done successfully.
  
  
2. Financial resource (Capital or Cost Resource)
2. Financial resource (Capital or Cost Resource)
The second essential resource for successful project completion is – capital.
As you know, all projects, regardless of their type, scale or complexity,
need money.
The cost resources are used for many things related to the project, including
project team members’ salaries, cost of tools and equipment that you and
your team will be using during the project execution.
Generally, managing a budget for a particular project is one of the core
skills that all project managers must have. As a project manager you need to
be confident handling finances and costs so that every phase of the project
goes smoothly.
One important aspect of this type of resource is for the project manager to
talk to its project sponsors about their expectations for the money that are
planned to be spent. It’s important that project sponsors have a realistic idea
about how much the project will cost, and as a project manager you can
help them do that once you have undertaken some of the planning.
     
     
 2.  Financial resource (Capital or Cost Resource)
 2.  Financial resource (Capital or Cost Resource)
If you don’t have enough finances for your project then you won’t be
able to get everything done. It’s that simple: the budget funds the
work and when it runs out the work has to stop. If they want the
project to be completed successfully then it needs to be adequately
funded.
You’ll need to know how much money you are spending because it
helps you establish whether you are on track or not.
                                   
 
 3.  
Material resources
Material resources
Projects also use up material resources that include different materials,
supplies and/or items that are part of the project. Assets, or goods, vary from
project to project but it’s highly likely that your project will need some kind of
tangible resource. It’s normally what you use the project budget to buy.
Equipment or machinery (which you might hire for the life of the project or
buy).
Property (again, it might be something you hire for the project such as a
temporary cabin on a building site).
Project managers can also make use of assets that the company already has
although they may have to budget for borrowing them or schedule in the right
time to use them so that they don’t clash with another project. An example
might be a testing lab that is used for multiple projects and that you will need
to book in advance in order not to coincide with other project teams using the
resource. This type of resource is particularly important to be planned in
advance because otherwise you can encounter huge problems for your project.
  
 3.2.3  Resource planning
 3.2.3  Resource planning
   1. What is resource planning?
   1. What is resource planning?
Resource planning is a specific area in project management that
deals with gathering and making use of all the necessary resources
required to deliver a project. In this respect, anything can be viewed
as a resource: people, equipment, materials and facilities.
Resource planning is also about managing available talent. It allows
project managers to make sure that one person will be working on
one thing, at one time, for a specific project. Managing resources is
also about matching skill level to task difficulty level. This way,
team members get to do challenging work and stay motivated.
  
 
2. 
2. 
Why is resource planning important in project management?
Why is resource planning important in project management?
Resources can make or break your project. Without the right resources, they
won’t turn into reality. Strategic use of resources allow project managers to
ship on time, respecting deadlines and costs. To this end, resource planning
is an essential step.
 Priorities can change on the fly. In order to accommodate changes, project
managers need to keep an eye on resource availability and utilization so
they can shift resources when needed.
It keeps an eye on utilization rates. This is very important if you charge
clients according to the number of hours.
It can help project managers to create balance and a good mood inside their
team. Matching tasks and skill set will keep team members happy and
engaged. Also, by constantly managing individual availability, project
managers make sure that work is divided equally and that no one gets
overworked.
      3.2.4  Resource levelling
      3.2.4  Resource levelling
Resource levelling 
is a technique in project management that overlooks
resource allocation and resolves possible conflict arising from over-
allocation. When project managers undertake a project, they need to
plan their resources accordingly. This will benefit the organization
without having to face conflicts and not being able to deliver on time.
Resource levelling is considered one of the key elements to resource
management in the organization.
                                         OR
Resource levelling 
is a project management technique in which the
demand for limited resources is accommodated by adjusting the project
program. In construction, resource levelling can be used to analyse the
variations in resource usage that can occur over time, and which can be
inefficient and costly.
       3.2.4  Resource levelling
       3.2.4  Resource levelling
                                           OR
Resource levelling
 is a technique in which start and finish dates are
adjusted based on 
resource
 constraints with the goal of balancing
demand for 
resources
 with the available supply.
                                          OR
Resource levelling
 is a PM technique’s which is begins and ends dates
is adjusted depends on 
resource
 restraints to the 
objectives
 of balance
the requirements for 
resources
 with presented supply.
                                          OR
Resource levelling
 is a technique in project management that overlooks
resource allocation and resolves possible conflict arising from over-
allocation. When project managers undertake a project, they need to
plan their resources accordingly
       3.2.5  Objectives of resource levelling
       3.2.5  Objectives of resource levelling
To allocate resource efficiently, so that the project can
be completed in the given time period
To overcome staff level constraints
To maximize the utilisation of resources between project
      3.2.6  Project crashing
      3.2.6  Project crashing
Project crashing 
is the process by which duration of project is reduced
by 
increasing
 the amount of 
resources
 allocated.
 
It can be used in the
management of construction works when the program is running behind
schedule. It is important to note that crashing is done only to 
critical
activities. This can be achieved by any one of the following approaches:
1)  Addressing productivity issues of the current resources and making
them more efficient. This can be done by taking better care of resources
available and cutting cost and time wherever possible.
2)  Bringing in new additional resources to speed up the processes.
3)  By evaluating alternatives available and analysing them in order to
find which one will help in compressing the duration with lowest cost.
3.2.6  Project crashing
3.2.6  Project crashing
Risks of Project Crashing in Project Management (PM) 
Risks of Project Crashing in Project Management (PM) 
1)  Various external and internal factors may lead project manager to go
for crashing but it usually affects the quality of work as the time taken
(besides cost) is the major issue on his mind.
2)  Using additional resources does not always guarantee better results.
Example if an organisation decides to hire more employees or outsource
them, one can't be sure that they are trained enough to deliver as per
expected standards which one will help in compressing the duration with
lowest cost.
  
3.2.7
3.2.7
 
Need for crashing
Need for crashing
   Project crashing can be necessary when:
The program planning has been inaccurate
When there have been unforeseen events which have caused delays,
such as defects being discovered.
Or if the client has requested that the projects, or a section of the
project, is completed earlier than previously specified, for example if
there has been an extension of time, but the client still wishes to
achieve the original completion date (this is generally referred to as
acceleration).
The aim of crashing is to achieve the maximum decrease in schedule for
minimum additional cost. This can be done by:
Addressing productivity issues being experienced by the current
resources and trying to find ways of increasing their efficiency.
3.2.7
3.2.7
 
Need for crashing
Need for crashing
Increasing the assignment of resources on critical path activities.
These could be internal resources or subcontracted resources.
Working longer hours.
Additional supervision.
Changes to design or specification (for example standardisation
replacing bespoke solutions)
Reduction in scope (for example transferring work to a separate
post-contract agreement for occupational work).
Early procurement of items.
           3.2.8  Tips for project crashing
           3.2.8  Tips for project crashing
Create project network
Identify the critical path
Identify the cost of reducing each activity on path
Reduce the most cost effective activity
Look for critical path changes i.e. if there is a multiple of critical
paths
 Crash next activity
          3.2.9  Principal Methods of crashing
          3.2.9  Principal Methods of crashing
Improving existing resources’ productivity
Changing work methods
Compromise quality/ reduce project scope
Work overtime
Increasing the quantity of resources
  
Scenarios to use crashing
Scenarios to use crashing
1.
 Imagine you are the Project Manager for XYZ project. You realize that
the project cannot be completed within 5 months. You decide to get
management's approval to add more resources to complete the project on
time, without changing the scope of the project. The technique used is?
Answer:
 
Crashing
Crashing
2.
 The Critical path of the project is 23 weeks. If the management wishes
to finish the project within 18 weeks. What is the impact on the term of the
critical path?
Answer
: If the management wishes to complete the project within 18
: If the management wishes to complete the project within 18
weeks, then the project slack will be- 18-23 = -5 weeks. The project slack
weeks, then the project slack will be- 18-23 = -5 weeks. The project slack
compares the critical path with an imposed date by the management, if
compares the critical path with an imposed date by the management, if
the project slack is negative, then you have an option to either perform
the project slack is negative, then you have an option to either perform
crashing or fast-track to ensure that the project is completed on time as
crashing or fast-track to ensure that the project is completed on time as
desired by the management. So, there will not be any changes in the
desired by the management. So, there will not be any changes in the
critical path.
critical path.
   
Scenarios to use crashing
Scenarios to use crashing
3.
 Crashing helps to bring the project back on schedule if it is delayed.
What should you do?
Answer:
 
Crashing should be done on the activities of the critical path
Crashing should be done on the activities of the critical path
of the project if you want to reduce the duration of the project.
of the project if you want to reduce the duration of the project.
4.
 The customer has given you a project to construct a building. The
project is delayed due to some unforeseen incidents and the customer has
demanded that you pay a penalty of 2,500,000Tshs, if you are not able to
complete the project on time. To avoid the penalty, you planned to work
overtime, add more human resources and rent physical resources to
complete the project on time. This is an example of:
Answer:
 
Crashing, as you have brought some extra resources to bring
Crashing, as you have brought some extra resources to bring
the project on track.
the project on track.
 
Scenarios to use crashing
Scenarios to use crashing
5.
 You are behind schedule by 3 months and you are under-budget
by  700,000Tshs. What is your best course of action?
Answer:
 
Since the project is delayed and I am under budget, I have
Since the project is delayed and I am under budget, I have
enough funds; and so, I can crash the project to make up for the
enough funds; and so, I can crash the project to make up for the
delay in the project schedule.
delay in the project schedule.
Scenarios to use crashing
Scenarios to use crashing
6.
 The project schedule network diagram for your project is as shown
in the figure below (duration is in days):
Scenarios to use crashing
Scenarios to use crashing
If Customer wants to complete this project within 14 days, what would
be the project float?
Answer:
Start→ Task 1→ Task 2→ Task 6→ End: 1+6+3+4=14 Days
Start→ Task 3→ Task 4→ Task 8→ End: 3+2+5+6=16 Days
Start→ Task 5→ Task 7→ Task 8 → End: 4+3+5+6=18 Days ->
This has Critical Path.
The duration on the critical path for the project is 18 days. If the
project has to be completed within 14 days, the project float is - 4
days; i.e., 14 - 18. So, Project Manager may either have the option to
perform crashing on the project schedule or otherwise, if the project
has a negative project float; i.e., -4 days).
     3.2.10  Time-Cost Trade-Off
     3.2.10  Time-Cost Trade-Off
The objective of the time-cost trade-off analysis is to reduce the
original project duration, determined from the critical path analysis,
to meet a specific deadline, with the least cost. In addition to that it
might be necessary to finish the project in a specific time to:
Finish the project in a predefined deadline date
Recover early delays
Avoid liquidated damages
Avoid adverse weather conditions that might affect productivity
Receive an early completion-bonus
Improve project cash flow
       3.2.10  Time-Cost Trade-Off
       3.2.10  Time-Cost Trade-Off
The activity duration can be reduced by one of the following actions:
Applying multiple-shifts work
Working extended hours (over time)
Offering incentive payments to increase the productivity
Working on week ends and holidays
Using additional resources
Using materials with faster installation methods
Using alternate construction methods or sequence
 
3.2.11  Project Costs
3.2.11  Project Costs
There are two types of costs associated with a project as here under:
 
(i) Direct costs
 
It represents the expenditure which can be allocated to different activi­
ties in a project, like manpower, material etc.
(ii) Indirect costs
It represents the expenditure on those items which are shared by more
than one activity and cannot be directly allocated to individual activity
of a project. Otherwise, one may say, indirect costs of a project are those
expenditures which cannot be apportioned or clearly allocated to the
individual activity. These include the expenditure related to the
administration and establishment charges, overhead, supervision, loss of
revenue etc.
                      1.  
Cost Slope and its significance in crashing
Cost Slope and its significance in crashing
In actual practice, we assume the time-cost curve to be linear between crash
point and nor­mal point. The curve in the figure below shows that, there is a
change in cost for change in time. The term ‘cost-slope’ is defined as the
in­crease in the cost of the activity per unit decrease in the time
.
        Mathematically, we can say,
        Cost slope = (Crash cost – Normal cost)/(Normal time – Crash time)
In simple words, we can say that 
cost slope of an activity is the increase in
cost of an activity by reducing the duration by one unit
.
                1. Cost Slope and its significance in crashing
                1. Cost Slope and its significance in crashing
   
   
Conducting a crash programme usually result in an increase in cost
of those activities that are constructed under the crash programme. In
order to keep the total increase in cost to a minimum, it is necessary
to crash those activities which permit reduction in construction time
at the least total increase in cost. The reduction in time for a project
can be achieved by reducing the duration of one or more activities
lying on the critical path.
The cost slope concept helps in finding lowest cost solution by
sequential compressing the activities having lowest cost slope, i.e.,
having lowest incremental cost, on critical path.
                      2.  Cost vs Time optimization curve
                      2.  Cost vs Time optimization curve
 
                              
                              
EXERCISE  3
EXERCISE  3
                         
                         
2 Marks questions
2 Marks questions
1.
What do you mean by scheduling in project management?
2.
 What are the uses of project schedule?
3.
Name the three project scheduling techniques.
4.
What do you understand by job layout?
5.
What do you know about WBC?
6.
What is a network diagram in project management?
7.
Name the two main types of network diagrams in project management.
8.
(i) What is an event?
     (ii) Mention two types of events
9.   What is an activity?
10.
 Define the slack.
11.
 What is resource management?
12.
 Mention the techniques used in resource management.
13.
 What are basic important types of resources in construction projects?
14.
What is resource planning?
15.
 Brief about resource levelling.
16.
 What do you know about project crashing?
17.
 For what purpose project crashing is needed?
18.
 State the general objective of time-cost trade-off analysis.
19.
 Name the two types of project costs.
20.  Define cost-slope and write it’s mathematical equation.
21.  Draw the cost-time optimization curve, label all the important features.
                               
                               
4 Marks questions
4 Marks questions
1.
Briefly explain the common steps in scheduling preparation.
2.
Classify project schedule.
3.
Discuss a Gantt chart with simple relevant diagram.
4.
Name and explain the principal preparation of job layout.
5.
What are the factors affecting job layout?
6.
Briefly explain any four (4) benefits of WBC.
7.
Explain the PDM.
8.
Using simple diagram, explain four (4) types of activities.
9.
Differentiate activity from event (at least 4 points).
10.
State the Fulkerson’s rule for numbering the events.
11.
Explain three time estimates of activity duration in PERT.
12.
Why do we need resource management?
15.
Explain in short about Critical Path, Earliest Start times, Earliest
Finish times, Latest Start times and Latest Finish times.
16.
Why is resource planning important in project management?
17. 
When is the project crashing necessary to be undertaken?
                                
                                
12 Marks questions
12 Marks questions
1.
Discuss in detail the temporary facilities needed to be constructed on
site.
2.
Enumerate the basic assumptions in creating a network diagram.
3.
Highlight and discuss the rules for drawing a network diagram.
4.
Differentiate PERT from CPM.
5.
What are the advantages and disadvantages of PERT?
6.
 Use the two tables below to: (a) Draw the PERT network diagram
(b) Calculate the expected time, variance and  standard deviation of
each activity (c) Draw the CPM network diagram (d) Calculate the
project completion time (e) Find the critical path (f) Identify the critical
activities.
                            END OF LECTURE 6
                            END OF LECTURE 6
                                   THANK YOU
                                   THANK YOU
                         
                         
SELESTIAN AUGUSTINO
SELESTIAN AUGUSTINO
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Critical Path Method (CPM) is a vital tool in project management for determining the longest sequence of tasks essential to complete a project within a specified timeframe. This method helps project managers identify tasks critical to project completion and allows for efficient scheduling and resource allocation. By calculating Early Start (ES), Early Finish (EF), Late Start (LS), and Late Finish (LF) times for each activity, project teams can pinpoint the project's critical path and potential areas for optimization. Understanding these concepts is crucial for effective project planning and execution.

  • Project Management
  • Critical Path Method
  • Task Sequencing
  • Project Scheduling
  • Resource Allocation

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  1. WELCOME TO LECTURE 6 SELESTIAN AUGUSTINO

  2. Try this question now: Draw a network diagram Immediate predecessor activity - Activity A B A C, D B E C F D G E, F

  3. 3.1.11 Critical Path Method ES, EF, LS, LF, FLOATS Early Start-ES Early Start or ES is the earliest time that activity can start. An activity near the end of path or much later will only start if all the previous activities in the path also started early. If any one of the previous activities slips then it will push this activity out. Early Finish-EF Early Finish or EF is the earliest time that activity can finish. It is the date that an activity can finish if all previous activities started early and none of the activities slipped. If project manager and team knows about early start and early finish dates of all the activities(tasks) then they will know how much freedom they have to move the start dates without causing any problem to the project.

  4. Tips for calculation of ES, EF during forward pass Forward pass is the direction from left to right as you traverse on network diagram. ES of first activity = 1 ES of all other activities = EF(of previous activity) + 1 If two activities say A and B converge (i.e. merge) to one activity, say C in forward pass, then ES of activity C = (greater EF from activity A and B) + 1 EF = ES + duration -1

  5. Sample diagram

  6. Late Start-LS Late Start or LS is the latest time an activity can start. If an activity is on the path which is much shorter compare to critical path, then it can start much late without any delay to the project. Late Finish-LF Late Finish or LF is the latest time that an activity can finish. If an activity is on a shorter path and all of the other activities on same path start as well as finish early, then it can finish very late without causing project to be late. Knowing late start and late finish will help you see how much it can be played around in the schedule. If an activity has large LS and LF means there are more options available.

  7. Tips for calculation of LS, LF during reverse pass Reverse/Backward pass is the direction from right to left as you traverse on network diagram. LF of last activity = EF of the same last activity For all other activities except the convergence mentioned in the next line, LF = LS(of previous activity) -1 If two activities say A and B converge (i.e. merge) to one activity in the reverse pass say C then, LF(of activity C) = (Lesser LS from activity A and B) -1 LS = LF - duration +1

  8. Sample diagram

  9. Problem 3: The following data are available for construction project. a) Construct a network diagram b) Calculate the project completion time c) Find the critical path and critical activities d) Determine the ES, EF, LS, LF and TF of each activity Immediate predecessor activity Activity duration (weeks) Activity A B C D E F - A A B C D,E 3 5 7 10 5 4

  10. Floats Float / Slack is the amount of time an activity or project can be delayed from the early start without changing the completion date of the project. Types of float 1.Total Float (TF) The amount of time that an activity can be delayed or extended from its early start date without delaying the project finish date or violating a schedule constraint. Mathematically: Late Finish Early Finish = Total Float 2. Free Float (FF) The amount of time that an activity can be delayed without delaying the early start date of any successor or violating a schedule constraint. Mathematically: Earliest Successors Early Start Activity s Early Finish = Free Float

  11. Floats 3. Interfering Float (INTF) The amount of time that an activity can be delayed or extended from its early start date without delaying the project finish date, but delaying an activity into interfering float will delay the start of one or more following non-critical activities. If an activity is delayed for the amount of the Free and Interfering Float, its successor activities are critical. Mathematically: Total Float Free Float = Interfering Float 4. Independent Float (INDF) The maximum amount of time an activity can be delayed without delaying the early start of the succeeding activities and without being affected by the allowable delay of any predecessor activity. Mathematically: Predecessors Late Finish Activity s duration = Independent Float Remark: when the result is a negative value, we set the value to zero.

  12. Advantages of CPM The CPM makes it easier for the project managers to build a team and create human network for efficient handling of a multi-tasked project. The Critical Path Method binds the entire team together and motivates the human resources in timely completion of the tasks in a project. The CPM takes into consideration the requirements well in advance to complete a project in the most efficient way possible. With help of the Critical Path Method the project managers can determine the duration and estimate exact time and cost of the project. It helps to monitor human resources, and the direct and indirect costs associated with the project. The CPM assists the project managers in planning schedules, monitoring tasks, and helps control the project expenses. The Critical Path Method also makes it convenient for the project managers to calculate the time required to complete the tasks of the project. That helps them to predict completion date of every phase, anticipate problems along the way, if any, and react accordingly.

  13. Disadvantages of CPM In a big project, a CPM can become extremely complicated and difficult to fathom for the new recruits to the project team. If the project is far too bulky and lengthy, the Critical Path Method requires software to monitor the plan. CPM can become ineffective and difficult to manage if it is not well-defined and stable. It cannot effectively handle sudden changes in the implementation of the plan on ground. It is very difficult to redraw the entire CPM chart if the plan of the project suddenly changes midway. The Critical Path Method cannot form and control the schedules of the persons involved in the project. The allocation of resources cannot be properly monitored. The critical path of the CPM of a big project is not always clear. The project managers have to spend a lot of time to calculate it carefully. The Critical Path Method takes longer to identity and to monitor the critical path when the project is of big dimension.

  14. Using CPM, identifying and determining a critical path is difficult when there are many other similar duration paths in the project. At times, to design a CPM is time consuming. It is also difficult to estimate the activity completion time in a multidimensional project. Self study 1. Enumerate the concrete significance of CPM (At least 4 points).

  15. 3.1.12 Time Estimation in PERT (With Calculation) There are three different estimates of activity duration in PERT: 1. Optimistic time 2. Pessimistic time 3. Most Likely time 1. Optimistic time, expressed as to , represents estimate of minimum possible time by which an activity can be completed assuming that everything is in order according to the plan and there can be only minimum amount of difficulty. 2. Pessimistic time, expressed as tp represents estimate of maximum possible time by which an activity can be completed assuming that things may not be in accordance with the plan and there can be incidence of difficulties in carrying out the activity. 3. Most Likely time, expressed as tm , represents estimate of time for completion of an activity, which is neither optimistic nor pessimistic, assuming that things should go in a normal way, and if the activity is repeated several times, in most of the cases, it will be completed in time represented by t.

  16. From the above three different time estimates, PERT suggests to work out the following; The expected time, expressed as (te) which is the average of to, tpand tmcalculated as, te= (to+ 4tm+ tp) / 6 The variance expressed as (Var.) , calculated as, Var.= ((tp-to)/6) The standard deviation expressed as ,which is the square root of variance (Var.) calculated as, = (Var.) = ((tp-to)/6) = (tp-to)/6

  17. Problem 4: Using the tabulated schedules below, a) Draw the PERT network diagram b) Calculate the expected time, variance and standard deviation of each activity c) Draw the CPM network diagram d) Calculate the project completion time e) Find the critical path f) Identify the critical activities

  18. Table 1

  19. Table 2

  20. Difference between PERT and CPM

  21. Self study 1. What are the advantages and disadvantages of PERT? (At least 5 points @)

  22. 3.2.0 Resource Management Resource is a stock or supply of money, materials, staff, and other assets that can be drawn on by a person or organization in order to function effectively. Resource management is the process of planning, scheduling, and allocating resources in the best possible way. The ultimate aim is to maximize the resources efficiency. This means, it ensures that internal and external resources are used effectively on time and to budget. OR Resource management is the process of planning the resources necessary to meet the objectives of the project, and to satisfy the client s requirements. OR Resource management is the efficient and effective development of an organization's resources when they are needed. Example: Financial resources, inventory, human skills, production resources, or information technology (IT) and natural resources. OR Resource management is acquiring, allocating and managing the resources, such as individuals and their skills, finances, technology, materials, machinery and natural resources required for a project.

  23. 3.2.1 Need for resource management Resource management is needed because: It provides the overview of everyone and everything involved in the project It enables utilization planning It makes the planning and management process more transparent It help you to see problems before they start It gives control over the project Techniques used in resource management are: 1. Resource Levelling 2. Resource Allocation 3. Resource Forecasting

  24. 3.2.2 Basic important types of resources in construction projects 1. Human resource 2. Financial resource 3. Material resource 4. Machinery resource

  25. 1. Human resource No matter the size and complexity of the project, in order for the project tasks to be performed effectively, human resources are essential. Human resources are considered to have the most complex requirements than the other two types of project resources. Therefore, project managers should plan in advance and identify potential people to become part of the project team by making sure they are available and skilled for the project in question. Normally a project team is a group of people that is managed by a project manager. The team management part is often the hardest part of the project, especially if the manager hasn t had to lead a team in the past. Managing the project team s time and workload can be tricky too, as, usually, most of the project team members don t work solely on one project. They often have day jobs and may be involved in other projects at the same time.

  26. 1. Human resource If you, as a project manager, know what individuals you need for your project it could be a lot easier to do your resource planning, which should help you balance those peaks and troughs of availability in the team. Spend some time thinking through the different skill sets that you need and the kind of tasks that are required for the project, regardless of the project complexity and type. Even at this early stage, you can still get a good idea of who needs to be involved. You ll have to work out who is needed on the project at what times, based on your project schedule. You ll need to bring in different types of subject matter experts at different times, and each one will have to know enough about the project s objectives to get their part done successfully.

  27. 2. Financial resource (Capital or Cost Resource) The second essential resource for successful project completion is capital. As you know, all projects, regardless of their type, scale or complexity, need money. The cost resources are used for many things related to the project, including project team members salaries, cost of tools and equipment that you and your team will be using during the project execution. Generally, managing a budget for a particular project is one of the core skills that all project managers must have. As a project manager you need to be confident handling finances and costs so that every phase of the project goes smoothly. One important aspect of this type of resource is for the project manager to talk to its project sponsors about their expectations for the money that are planned to be spent. It s important that project sponsors have a realistic idea about how much the project will cost, and as a project manager you can help them do that once you have undertaken some of the planning.

  28. 2. Financial resource (Capital or Cost Resource) If you don t have enough finances for your project then you won t be able to get everything done. It s that simple: the budget funds the work and when it runs out the work has to stop. If they want the project to be completed successfully then it needs to be adequately funded. You ll need to know how much money you are spending because it helps you establish whether you are on track or not.

  29. 3. Material resources Projects also use up material resources that include different materials, supplies and/or items that are part of the project. Assets, or goods, vary from project to project but it s highly likely that your project will need some kind of tangible resource. It s normally what you use the project budget to buy. Equipment or machinery (which you might hire for the life of the project or buy). Property (again, it might be something you hire for the project such as a temporary cabin on a building site). Project managers can also make use of assets that the company already has although they may have to budget for borrowing them or schedule in the right time to use them so that they don t clash with another project. An example might be a testing lab that is used for multiple projects and that you will need to book in advance in order not to coincide with other project teams using the resource. This type of resource is particularly important to be planned in advance because otherwise you can encounter huge problems for your project.

  30. 3.2.3 Resource planning 1. What is resource planning? Resource planning is a specific area in project management that deals with gathering and making use of all the necessary resources required to deliver a project. In this respect, anything can be viewed as a resource: people, equipment, materials and facilities. Resource planning is also about managing available talent. It allows project managers to make sure that one person will be working on one thing, at one time, for a specific project. Managing resources is also about matching skill level to task difficulty level. This way, team members get to do challenging work and stay motivated.

  31. 2. Why is resource planning important in project management? Resources can make or break your project. Without the right resources, they won t turn into reality. Strategic use of resources allow project managers to ship on time, respecting deadlines and costs. To this end, resource planning is an essential step. Priorities can change on the fly. In order to accommodate changes, project managers need to keep an eye on resource availability and utilization so they can shift resources when needed. It keeps an eye on utilization rates. This is very important if you charge clients according to the number of hours. It can help project managers to create balance and a good mood inside their team. Matching tasks and skill set will keep team members happy and engaged. Also, by constantly managing individual availability, project managers make sure that work is divided equally and that no one gets overworked.

  32. 3.2.4 Resource levelling Resource levelling is a technique in project management that overlooks resource allocation and resolves possible conflict arising from over- allocation. When project managers undertake a project, they need to plan their resources accordingly. This will benefit the organization without having to face conflicts and not being able to deliver on time. Resource levelling is considered one of the key elements to resource management in the organization. OR Resource levelling is a project management technique in which the demand for limited resources is accommodated by adjusting the project program. In construction, resource levelling can be used to analyse the variations in resource usage that can occur over time, and which can be inefficient and costly.

  33. 3.2.4 Resource levelling Resource levelling is a technique in which start and finish dates are adjusted based on resource constraints with the goal of balancing demand for resources with the available supply. OR Resource levelling is a PM technique s which is begins and ends dates is adjusted depends on resource restraints to the objectives of balance the requirements for resources with presented supply. OR Resource levelling is a technique in project management that overlooks resource allocation and resolves possible conflict arising from over- allocation. When project managers undertake a project, they need to plan their resources accordingly OR

  34. 3.2.5 Objectives of resource levelling To allocate resource efficiently, so that the project can be completed in the given time period To overcome staff level constraints To maximize the utilisation of resources between project

  35. 3.2.6 Project crashing Project crashing is the process by which duration of project is reduced by increasing the amount of resources allocated. It can be used in the management of construction works when the program is running behind schedule. It is important to note that crashing is done only to critical activities. This can be achieved by any one of the following approaches: 1) Addressing productivity issues of the current resources and making them more efficient. This can be done by taking better care of resources available and cutting cost and time wherever possible. 2) Bringing in new additional resources to speed up the processes. 3) By evaluating alternatives available and analysing them in order to find which one will help in compressing the duration with lowest cost.

  36. 3.2.6 Project crashing Risks of Project Crashing in Project Management (PM) 1) Various external and internal factors may lead project manager to go for crashing but it usually affects the quality of work as the time taken (besides cost) is the major issue on his mind. 2) Using additional resources does not always guarantee better results. Example if an organisation decides to hire more employees or outsource them, one can't be sure that they are trained enough to deliver as per expected standards which one will help in compressing the duration with lowest cost.

  37. 3.2.7Need for crashing Project crashing can be necessary when: The program planning has been inaccurate When there have been unforeseen events which have caused delays, such as defects being discovered. Or if the client has requested that the projects, or a section of the project, is completed earlier than previously specified, for example if there has been an extension of time, but the client still wishes to achieve the original completion date (this is generally referred to as acceleration). The aim of crashing is to achieve the maximum decrease in schedule for minimum additional cost. This can be done by: Addressing productivity issues being experienced by the current resources and trying to find ways of increasing their efficiency.

  38. 3.2.7 Need for crashing Increasing the assignment of resources on critical path activities. These could be internal resources or subcontracted resources. Working longer hours. Additional supervision. Changes to design or specification (for example standardisation replacing bespoke solutions) Reduction in scope (for example transferring work to a separate post-contract agreement for occupational work). Early procurement of items.

  39. 3.2.8 Tips for project crashing Create project network Identify the critical path Identify the cost of reducing each activity on path Reduce the most cost effective activity Look for critical path changes i.e. if there is a multiple of critical paths Crash next activity

  40. 3.2.9 Principal Methods of crashing Improving existing resources productivity Changing work methods Compromise quality/ reduce project scope Work overtime Increasing the quantity of resources

  41. Scenarios to use crashing 1. Imagine you are the Project Manager for XYZ project. You realize that the project cannot be completed within 5 months. You decide to get management's approval to add more resources to complete the project on time, without changing the scope of the project. The technique used is? Answer: Crashing 2. The Critical path of the project is 23 weeks. If the management wishes to finish the project within 18 weeks. What is the impact on the term of the critical path? Answer: If the management wishes to complete the project within 18 weeks, then the project slack will be- 18-23 = -5 weeks. The project slack compares the critical path with an imposed date by the management, if the project slack is negative, then you have an option to either perform crashing or fast-track to ensure that the project is completed on time as desired by the management. So, there will not be any changes in the critical path.

  42. Scenarios to use crashing 3. Crashing helps to bring the project back on schedule if it is delayed. What should you do? Answer: Crashing should be done on the activities of the critical path of the project if you want to reduce the duration of the project. 4. The customer has given you a project to construct a building. The project is delayed due to some unforeseen incidents and the customer has demanded that you pay a penalty of 2,500,000Tshs, if you are not able to complete the project on time. To avoid the penalty, you planned to work overtime, add more human resources and rent physical resources to complete the project on time. This is an example of: Answer: Crashing, as you have brought some extra resources to bring the project on track.

  43. Scenarios to use crashing 5. You are behind schedule by 3 months and you are under-budget by 700,000Tshs. What is your best course of action? Answer: Since the project is delayed and I am under budget, I have enough funds; and so, I can crash the project to make up for the delay in the project schedule.

  44. Scenarios to use crashing 6. The project schedule network diagram for your project is as shown in the figure below (duration is in days):

  45. Scenarios to use crashing If Customer wants to complete this project within 14 days, what would be the project float? Answer: Start Task 1 Task 2 Task 6 End: 1+6+3+4=14 Days Start Task 3 Task 4 Task 8 End: 3+2+5+6=16 Days Start Task 5 Task 7 Task 8 End: 4+3+5+6=18 Days -> This has Critical Path. The duration on the critical path for the project is 18 days. If the project has to be completed within 14 days, the project float is - 4 days; i.e., 14 - 18. So, Project Manager may either have the option to perform crashing on the project schedule or otherwise, if the project has a negative project float; i.e., -4 days).

  46. 3.2.10 Time-Cost Trade-Off The objective of the time-cost trade-off analysis is to reduce the original project duration, determined from the critical path analysis, to meet a specific deadline, with the least cost. In addition to that it might be necessary to finish the project in a specific time to: Finish the project in a predefined deadline date Recover early delays Avoid liquidated damages Avoid adverse weather conditions that might affect productivity Receive an early completion-bonus Improve project cash flow

  47. 3.2.10 Time-Cost Trade-Off The activity duration can be reduced by one of the following actions: Applying multiple-shifts work Working extended hours (over time) Offering incentive payments to increase the productivity Working on week ends and holidays Using additional resources Using materials with faster installation methods Using alternate construction methods or sequence

  48. 3.2.11 Project Costs There are two types of costs associated with a project as here under: (i) Direct costs It represents the expenditure which can be allocated to different activi- ties in a project, like manpower, material etc. (ii) Indirect costs It represents the expenditure on those items which are shared by more than one activity and cannot be directly allocated to individual activity of a project. Otherwise, one may say, indirect costs of a project are those expenditures which cannot be apportioned or clearly allocated to the individual activity. These include the expenditure related to the administration and establishment charges, overhead, supervision, loss of revenue etc.

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