PM Chapter 09 Scheduling Resources

7/27/2019 PM Chapter 09 Scheduling Resources

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Project ManagementScheduling Resources


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Scheduling Resources

Project network times are not a schedule untilresources have been assigned to them.


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There are always more project proposals than

there are available resources.

The priority system needs to select projects that

best contribute to the organizations objectives,

within the constraints of resources available.

In this lecture, we will examine the methods of

scheduling resources so that team can make

realistic judgments of resource availability

and project durations.

The project manager uses the same schedule for

implementing the project. If changes occur duringproject implementation, the computed schedule

is easily updated and the effects easily assessed.


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Planned network and activity project durations

times fail to deal with resource usage and

availability.

The time estimate for the work packages and

network times were made independently with

the implicit assumptions that resources would be

available. This may or may not be the case.

If resources are adequate but the demand varies

widely over the life of the project, it may be

desirable to even out resource demand by delaying

non-critical activities (using slack) to lower

peak demand and thus increase resourceutilization. This is called resource levelingor

smoothing.


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On the other hand, if resources are not adequate to

meet peak demands, the late start of some

activities must be delayed and the duration of theproject may be increased. This process is called

resource-constrained scheduling.

This lecture mainly deals with methods available

to project managers for dealing with resource

utilization and availability through resource

leveling and resource constrained scheduling.


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Types of Project Constraints

Project constraints impede or delay the start of

activities. The result is a reduction in slack shown

on the planned network, a decrease in schedulingflexibility, a possible decrease in the number of

parallel activities and an increase in the likelihood

of delaying the project.

Three project constraints need to be considered

in scheduling:

Technical or logic constraint

Physical constraint

Resource constraints


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Technical Constraint

These constraints usually address thesequence in which project activities must

occur.

You cannot logically perform activity 2 unless

activity 1 is complete.

Start Design Code Test End


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Physical Constraint

In rare cases, there are physical constraintsthat cause activities that would normally

occur in parallel to be constrained by

contractual or environmental conditions.


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Resource Constraint

The absence or shortage of resources can drastically alter technicalconstraints. A project network planner may assume adequate

resources and show activities occurring in parallel. However, parallel

activities hold potential for resource conflicts.

Due to constraints parallel activities are changed to sequential.

Hire

Band

Decorate

Hall

Purchase

Food

Plan

Hire

Band

Decorate

Hall

Purchase

Food

Reception

Plan Reception


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Resource Constraint

The consequence is a delay of activities anda very different set of network relationships.

Note that the resource dependencies take

priority over technical dependencies but

does not violate the technical dependency.

A deficit of resources can significantly

alter project dependency relationships,

completion dates and project costs.


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Kinds of Resource Constraint

Resources are people, equipment and material that can be drawn on toaccomplish something.

In project, the availability or unavailability of resources will often influence

the way projects are managed.

The major resources that a project manager must manage on a daily basis

are people, material equipmentand working capital.


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People

Actually classified by the skill they bring to theproject.

In rare cases, some skills are interchangeable, but

usually with a loss of productivity.

The many different skills of human resources

add to the complexity of scheduling projects.


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Material

Cover a large spectrumfor example, chemicals,concrete, cement, survey data for a marketing

project.


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Equipment

Equipment is usually presented by type, size andquantity. In some cases, equipment can be

interchanged to improve schedules.

The most common oversight is to assume the

resource pool is more than adequate for the

project.


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Working Capital

In a few project situations such as construction,working capital is treated as a resource because

it is limited in supply.

If working capital is readily available, a project

manager may work on may activities concurrently.

If working capital is in short supply, material and

labor usage may have to be restricted.


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Scheduling Problems

Most of the scheduling methods available todayrequire the project manager to classify the project

as either:

A time-constrained projecta one that must be

completed by an imposed date. If required,

resources can be added to ensure that the project

is completed by a specific date. Project duration

is fixed and resources are flexible.

A resource-constrained projectone that assumes

that level of resources cannot be exceeded. If the

resources are inadequate, it will be acceptable to

delay the project but as little as possible.


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Resource Allocation Methods

Assumptions

Splitting of activities is not allowed. Once the

activity is placed in a schedule, it will be worked

on continuously until it is finished.

Level of resources used for an activity cannot be

changed.


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Time-constrained Projects - Smoothing Resource Demands

Scheduling time constrained projects focuses on resource utilization.

When demand for a specific resource type is erratic, it is difficult to

manage, and utilization may be poor.

Project managers have attacked the utilization problem using resource

leveling techniques that balance or smooth demands for resource.

Basically all leveling techniques delay non-critical activities by using

positive slack to reduce peak demand and fill in the valleys for the

resources.


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ExampleBotanical Garden

Design

Layout

Walkways

Lighting

Irrigation

Fence / WallsPlanting

0 2 4 6 8 10 12 14 16 18 20 22 24

2 bh

1 bh

1 bh

2 bh

1 bh

3 bh

Number

of Backhoes

Required

0

4

3

2

1


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ExampleBotanical GardenTrial #1 Shifting the Irrigation Activity

Design

Layout

Walkways

Lighting

Irrigation


0 2 4 6 8 10 12 14 16 18 20 22 24

2 bh

1 bh

1 bh

2 bh

1 bh

3 bh

Number

of Backhoes

Required

0

4

3

2

1


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ExampleBotanical GardenTrial #2 Shifting Fence / Walls Activity

Design

Layout

Walkways

Lighting

Irrigation


0 2 4 6 8 10 12 14 16 18 20 22 24

2 bh

1 bh

1 bh

2 bh

1 bh

3 bh

Number

of Backhoes

Required

0

4

3

2

1


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The letter solution improves the utilization of resources.

Backhoes are not easily moved from location to location.

There are costs associated with changing the level of resources needed.

The same analogy applies to the movement of people back and forth

among projects.

It is a well known fact that people are more efficient if they can focus

their effort on one project rather than multitasking their time among

multiple projects.

Downside if a loss of flexibility that occurs from reducing the slack.

The risk of delaying activities delaying project also increases because

slack reduction can create more critical activities and / or near critical

activities. Pushing leveling too far for a perfectly level resource profile

is risky. Every activity becomes critical.


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In practice, smoothing a project with thousands of activities can onlybe achieved by software.

These software have good routines for leveling project resource.

Typically they use activities that have the most slack to level project

resources.

It is easy to experiment with many alternatives to find the one that best

fits your project and minimize risk of delaying the project..


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Resource-constrained Projects

When the number of people and / or equipment is not adequate to meetpeak demand requirements and it is impossible to obtain more, the

project manager faces a resource constrained problem. Something has to

give. The trick is to prioritize and allocate resources to minimize project

delay without exceeding the resource limit or altering the technical

network relations.


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The resource scheduling problem is a large combinatorial one. This meanseven a modest size project network with only a few resources types

might have many feasible solutions. .

Researchers have demonstrated optimum mathematical solution to the

resource allocation problem but only for a small network and very few

resource types.

Massive data requirements for larger problems make pure mathematical

solution impractical.

An alternative approach to the problem has been the use of heuristics.


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Heuristics do not always yield an optimal solution, but they are capableof yielding a good schedule for a very complex network with many types

of resources.

It is possible to test several sets of heuristics on a network and then

determine priority allocation rules that minimize project delays.

Compute software available today makes it very easy for the project

manager to create a good resource schedule for the project.

R All ti M th d


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Heuristics allocate resources to activities to minimize project delay.

They prioritize which activities are allocated resources and which

activities are delayed when resources are not adequate.

The following scheduling heuristics have been found to consistently

minimize project delay over a large variety of projects.

Schedule activities using the following heuristics priority rules in the order

presented.

Minimum slack

Smallest duration

Lowest activity number

R All ti M th d


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The parallel method is used most widely to apply heuristics.

It is an iterative process that starts at the first time period of the project

and schedules period by period any activities eligible to start.

In any period, when two or more activities require the same resource,

priority rules mentioned previously are applied.

When the resource limit has been reached, the early start for succeeding

activities not yet in the schedule will be delayed (and all successor

activities not having free slack) and their slack reduced.

In subsequent periods, the process is repeated until the project is

scheduled.

R All ti M th d


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ES EFID

LS LFDur

SL

A

2F

4

C

4

B

6E

2

Legend

G

2

0 2

2

2

8

6

6 8

6 10

10 12

1210

10

10

8

6

62

104

20

0

2

2

00

0

Example


D

2

2 4

108

6

Resources

2 Persons

2 Persons

2 Persons

1 Person

1 Person

1 Person

Resource constraint: total resources available are 3 persons

1 Person

R All ti M th d


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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

2

2

2

6

6

10

2

10

6

10

10

10

12

0

2

0

6

2

0

0

ES Resource Load Chart

2 2

2 2 2 2 2 2

2 2 2 2

1 1

1 1

1 1 1 1

1 1

2P 2P 5P 5P 4P 4P 4P 4P 1P 1P 1P 1P

Available Resources 3P 3P 3P 3P 3P 3P 3P 3P 3P 3P 3P 3P

R All ti M th d


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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

2

2

2

6

6

10

2

10

6

10

10

10

12

0

2

0

6

2

0

0

Resource Constrained Schedule

2 2

2P 2P


Period 01, only activity A is eligible, it requires 2 persons. Load it into the schedule.

R All ti M th d


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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

2

2

2

6

6

10

2

10

6

10

10

10

12

0

2

0

6

2

0

0


2 2

2P 2P


Period 12, no activity is eligible.

Reso rce Allocation Methods


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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

3

2

2

6

6

10

2

10

6

10

10

10

12

0

1

0

6

2

0

0


2 2

2P 2P


Period 23, activities B, C, and D are eligible to be scheduled. Activity C has the least

slack (0), therefore, apply rule 1 and schedule activity C. Activity B is next with a slack 2,

however, it requires 2 persons and only 1 is available. Delay activity B and update itsES=3 and slack=1. Next eligible activity is D, since it only needs one person, so load it.

2 2 2 2

1 1

3P 3P 2P 2P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

4

2

2

6

6

10

2

10

6

10

10

10

12

0

0

0

6

2

0

0


2 2

2P 2P


Period 34, activity B is eligible but exceeds limit of 3 persons. Delay activity B, update

ES=4 and slack = 0.

2 2 2 2

1 1

3P 3P 2P 2P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

5

2

2

6

6

11

2

11

6

10

10

10

13

0

-1

0

6

2

0

-1


2 2

2P 2P



ES=5 and slack = -1. Also, since activity G is a successor activity, it is also delayed.

Update ES=11 and slack =-1.

2 2 2 2

1 1

3P 3P 2P 2P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

6

6

12

2

12

6

10

10

10

12

0

-2

0

6

2

0

-2


2 2

2P 2P



ES=6 and slack = -2. Also, since activity G is a successor activity, it is also delayed.

Update ES=12 and slack =-2.

2 2 2 2

1 1

3P 3P 2P 2P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

7

6

12

2

12

6

10

10

10

12

0

-2

0

6

1

0

-2


2 2

2P 2P


Period 67, activities B, E and F are eligible with slack of -2, 2, and 0 respectively. Load B

into schedule (rule 1), Activity F with slack 0 is the next eligible activity. Load F into schedule.

Limit of 3 persons is reached, so delay activity E. Update ES = 7 and slack = 1.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

8

6

12

2

12

6

10

10

10

14

0

-2

0

6

0

0

-2


2 2

2P 2P


Period 78, limit is reached, no person available. Delay activity E. Update ES=8 and slack=0

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

9

6

12

2

12

6

10

11

10

12

0

-2

0

6

-1

0

-2


2 2

2P 2P


Period 89, limit is reached, no person available. Delay activity E. Update ES=9 and slack=-1.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

10

6

12

2

12

6

10

12

10

12

0

-2

0

6

-2

0

-2


2 2

2P 2P


Period 910, limit is reached, no person available. Delay activity E. Update ES=10 and

slack=-2.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

10

6

12

2

12

6

10

12

10

12

0

-2

0

6

-2

0

-2


2 2

2P 2P


Period 1011, Activity E is eligible, so load it into schedule.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P

1 1

3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

10

6

12

2

12

6

10

12

10

12

0

-2

0

6

-2

0

-2


2 2

2P 2P


Period 1112, no activity.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P

1 1

3P 3P



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Example


ID RES DUR ES LF TS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A

B

C

D

E

F

G

Total Resource Load

2P

2P

2P

1P

1P

1P

1P

2

6

4

2

2

4

2

0

6

2

2

10

6

12

2

12

6

10

12

12

14

0

-2

0

6

-2

2

-2


2 2

2P 2P


Period 1213, Activity G is eligible, so load it into schedule.

2 2 2 2

1 1

3P 3P 2P 2P

1 1 1 1

2 2 2 2 2 2

3P 3P 3P 3P

1 1

3P 3P

1 1

1P 1P

3P 3P



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ES EFID

LS LFDur

SL

A

2F

4

C

4

B

6E

2

Legend

G

2

0 2

6

2

12

6

10 12

6 10

12 14

1412

12

12

10

8

62

126

20

0

0

0

00

2

Example


D

2

2 4

108

6

Resources

2 Persons

2 Persons

2 Persons

1 Person

1 Person

1 Person

Splitting or Multitasking


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Splitting or multitasking is a scheduling technique

used to get a better project schedule and / or to

increase resource utilization.

A planner splits the continuous work included in

an activity by interrupting the work and sending

the resources to another activity for a period of

time and then having the resource resume work on

the original activity.

Splitting is useful tool if the work involved does

not include large start-up or shut-down costs.

The most common error is to split people work

where there are high conceptual start up andshutdown costs. The cost may be hidden but real.



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The illustration depicts the nature of the

splitting problem. The original activity has been

split into three separate activities: A, B and C.The shutdown and start-up times lengthen the time

for the original activity.

Propensity to deal with resource shortages by

multitasking is a reason why projects fail to meet

schedules.

Avoid splitting as much as possible, except in

situations where the cost of splitting are known

to be small or where there is no alternative.

Activity duration without splitting

Activity duration split into three

activitiesA, B and C.

A B C

Activity duration split into three

activitiesA, B and Cwith

shutdown and startup.

A B C

Startup Shutdown

Assigning Project Work


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When making individual assignments, project

managers should match, as best they can, the

demands and requirements of specific workwith the qualification and experience of available

participants.

In doing so, there is a natural tendency to assign

the best people to most difficult tasks.

Project managers need to be careful not to overdo

this.

Over time these people may grow to resent the

fact that they are always given the toughest

assignments.

At the same time less experience participants

may resent the fact that they are never given

the opportunity to expand their skill knowledge

base.



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Project managers need to balance task

performance with the need to develop the talents

of people assigned to the project.

Project managers also decides who works with

whom. To minimize unnecessary tension,

managers should pick people with compatible

work habits and personalities but who complement

each others.Veterans should be teamed up with new hires

not only so they can share their experience but

also to help socialize the newcomers to the

customs and norms of the organization.

Future needs should also be considered. If twopeople who have never worked together before but

will work together later on in the project, it may

be wise to team them up as early in the project

as possible so that can become familiar with

each other.

Multiple Resource Schedules


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In reality resource allocation generally occurs in a

multi-project environment where the demands of

one project have to be reconciled with the needs ofthe other projects.

Organizations must develop and manage systems

for efficiently allocating and scheduling resources

across several projects with different priorities,

resource requirements, sets of activities and risks.

The system must be dynamic and capable of

accommodating new projects as well as

reallocating resources once project work is

completed.

While the same resource issues and principles

that apply to a single project also apply to a

multi-project environment, applications and

solutions are more complex, given the

dependencies among projects.



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Problems encountered in managing multi-project

resource schedules:

Overall schedule slippage

Inefficient resource utilization

Resource bottlenecks

To deal with these problems, more and more

companies create project offices or departments

to oversee the scheduling of resources across

multiple projects.



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One approach to multiple project resource

scheduling is to use a first come first served

rule.

A project queue system is created in which project

currently underway take precedence over new

projects. However, it does not optimally utilize

resources or take into account the priority of the

project.

Many companies use more elaborate processes

for scheduling resources to increase the capacity

of the organization to initiate projects. Most of

these methods approach the problem by treating

individual project as part of one big project andadapting the scheduling heuristics previously

introduced to this mega-project.



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p

Project schedulers monitor resource usage and

provide updated schedules based on progress and

resource availability across all projects.

One major improvement in project management

software in recent years is the ability to prioritize

resource allocation to specific projects.

Projects are prioritized and these priorities willoverride scheduling heuristics so that resources

go to the project highest in the priority lists.

Centralized project scheduling also makes it easier

to identify resource bottlenecks that restrain

progress on project.

Once identified, the impact of the bottlenecks

can be documented and can be used to justify

acquiring additional equipment, recruiting critical

personnel or delaying the project.

Documents

PM Chapter 09 Scheduling Resources