Scheduling Resources and Costs

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Scheduling Resources and Costs

• Chapter 8

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The Resource Problem

• Resources and Priorities
• Project network times are not a schedule until
  resources have been assigned.
• The implicit assumption is that resources will be
  available in the required amounts when needed.
• Adding new projects requires making realistic
  judgments of resource availability and project
  durations.
• Resource-Constrained Scheduling
• Resource leveling (or smoothing) involves
  attempting to even out demands on resources by
  using slack (delaying noncritical activities) to
  manage resource utilization.

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Types of Project Constraints

• Technical or Logic Constraints
• Constraints related to the networked sequence in
  which project activities must occur
• Resource Constraints
• The absence, shortage, or unique
  interrelationship and interaction characteristics
  of resources that require a particular sequencing
  of project activities

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Constraint Examples
FIGURE 8.1
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Kinds of Resource Constraints

• People
• Materials
• Equipment
• Working Capital

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Classification of a Scheduling Problem

• Classification of Problem
• Using a priority matrix will help determine if
  the project is time or resource constrained
• Time-Constrained Project A project that must be
  completed by an imposed date
• Time is fixed, resources are flexible if
  additional resources are required to ensure
  project meets schedule, they may be obtainable
• Or a
• Resource-Constrained Project A project in which
  the level of resources available cannot be
  exceeded
• Resources are fixed, time is flexible inadequate
  resources will simply delay the project.

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Resource Allocation Methods

• Limiting Assumptions
• Splitting activities is not allowedonce an
  activity is start, it is carried to completion.
• Level of resource used for an activity cannot be
  changed.
• Activities with the most slack pose the least
  risk.
• Reduction of flexibility does not increase risk.
• The nature of an activity (easy, complex) doesnt
  increase risk.
• (Aside) From practical observation, the way many
  PMs handle resource allocation is to assign
  people to activities after the network has been
  MSProject-ized, and then filter for person and
  put in additional links.
• While easy to do, this is not theoretically
  correct and leads to over-restrictive scheduling
  or inability to react to personnel changes.

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Time-Constrained Projects

• Are projects that must be completed by an
  imposed date
• Require the use of leveling techniques that focus
  on balancing or smoothing resource demands by
  using (positive) slack (i.e. delaying noncritical
  activities) to manage resource utilization over
  the duration of the project
• Peak resource demands are reduced.
• Resources over the life of the project are
  reduced.
• Fluctuation in resource demand is minimized.

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Botanical Garden Example

• Given the following project network, we would
  like to
• minimize total resources (rented backhoes) used
• smooth capacity requirements (avoid large
  fluctuations)

FIGURE 8.2
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Pre and Post Smoothing
FIGURE 8.2 (contd)
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Resource Allocation Methods

• Resource Demand Leveling Techniques for
  Time-Constrained Projects
• Advantages
• Peak resource demands are reduced.
• Resources over the life of the project are
  reduced.
• Fluctuation in resource demand is minimized.
• Disadvantages
• Loss of flexibility that occurs from reducing
  slack
• Increases in the criticality of all activities

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Resource-Constrained Projects

• Are projects that involve resources that are
  limited in quantity or by their availability
• Scheduling of activities through use of
  heuristics (rules-of-thumb), according to the
  following priorities.
• Note- Heuristics do not guarantee optimal
  solutions, but they help in finding a decent
  solution quickly
• Start from beginning of project time and, when
  resources used exceed the resources available,
  retain activities first by
• Minimum slack
• Smallest (least) duration
• Lowest activity identification number
• and push the others out further in time
• An unarticulated rule in later periods, do not
  move activities that have already started
• Additional caveat when considering activities
  not to delay, consider the resources each
  activity uses.

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Example Resource Constrained Project

• Assume we only have 3 people available to do the
  following project, and we cannot afford to hire
  more.

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Example of Resource-Constrained Scheduling
a2
a5
a1
a7
a3
a6
a4
Suggestion for improving notation- prefix
activity IDs with a to keep s from overwhelming
FIGURE 8.3
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Prior to Resource Balancing
ES resource load chart (with slack in gray)
Revisions from book, to make process clearer
FIGURE 8.3 (contd)
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View Resources in MS Project

• In Resource Graph can see the overage
• Set resource availability via view resource
  sheet
• Defaults to increments of 50 but you can
  manually type in different amounts

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Start Shifting Activities Later to Satisfy
Resource Availability
Resource-constrained schedule through period 56
2 2 2 2 2 2
1 1
1 1 1 1
1 1
FIGURE 8.4
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We Now Consider the Resources Available
Delay activity 2 by 1 period, making 2-to-3
period resource- feasible (still not feasible for
3-to-4 and beyond.)
2 2 2 2 2 2
1 1
1 1 1 1
1 1
FIGURE 8.3 (contd)
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Resource Load Now Feasible

• Final resource-constrained schedule
• Still need to re-compute slack, given new project
  end date

FIGURE 8.4 (contd)
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Example in MS-Project

• Go to tools level resources
• For resource-constrained leveling, use the
  default settings
• For time-constrained, pick Level within Slack
  and ignore the working messages that may be
  produced
• Will produce a schedule with less fluctuation,
  but may still exceed level limits

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(Another) Computer Demonstration
ofResource-Constrained Scheduling

• EMR Project
• The development of a handheld electronic medical
  reference guide to be used by emergency medical
  technicians and paramedics
• Problem
• There are only eight design engineers who can be
  assigned to the project due to a shortage of
  design engineers and commitments to other
  projects.

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EMRProject NetworkView of Schedule before
Resources Leveled
This is the illustration from the book, which
has 2 grievous errors- Can anyone spot them?
FIGURE 8.5
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EMR Project Prior to Leveling Resources
FIGURE 8.6
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Time Constrained Leveling Within Slack

• We reduce the need for some overtime
• but still have a large peak at the end, so this
  is probably not acceptable

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Leveling by Allowing the Project Duration to
Expand

• If we take MS Projects leveling defaults
• Project duration will now be 57 working days
  instead of 45 working days.
• Assuming a 1/2/08 start and no special holidays,
  we go from ending on 3/4 to 3/20
• Resource usage between 5 to 8 engineers
• Can insert leveling delay column in schedule
  view to see the shifts
• Even manually make them without relying on MS
  algorithms.

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The Impacts of Resource-Constrained Scheduling

• Reduces delay but reduces flexibility
• Increases sensitivity of the network
• Increases scheduling complexity
• Can break the sequence of events
• May cause parallel activities to become
  sequential and change the critical path

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Splitting/Multi-tasking

• A scheduling technique use to get a better
  project schedule and/or increase resource
  utilization
• Involves interrupting work on an activity to
  employ the resource on another activity, then
  returning the resource to finish the interrupted
  work
• Is feasible when startup and shutdown costs are
  low (must include them)
• Although easy to put in with project software,
  both prof and book would argue this is not a good
  approach.

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Assigning Project Work

• Factors to Consider
• Dont always pick the same people for the
  toughest assignments.
• Choose people with an eye to fostering their
  development through participation on the project.
• Pick people with compatible work habits and
  personalities but who are not identical- can
  complement each other.
• Mix team-up veterans with new hires to share
  experience and socialize newcomers into the
  organization.
• Select people who may need to learn work together
  on later stages of the project or other projects.

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Multiproject Resource Schedules

• Multiproject Scheduling Problems
• Overall project slippage
• Delay on one project creates delays for other
  projects.
• Inefficient resource application
• The peaks and valleys of resource demands create
  scheduling problems and delays for projects.
• Resource bottlenecks
• Shortages of critical resources required for
  multiple projects cause delays and schedule
  extensions.

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Multiproject Resource Schedules

• Managing Multiproject Scheduling
• Create project offices or departments to oversee
  the scheduling of resources across projects.
• Use a project priority queuing system first
  come, first served for resources.
• Prioritize based on perceived need- Internal
  projects more likely to get slipped than
  client-facing ones.
• Centralize project management treat all projects
  as a part of a mega-project.
• Outsource projects to reduce the number of
  projects handled internally.

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Group Exercise

• Old Test Question
• Given the following
• table and the fact
• that we have 4
• coders on staff
• Before smoothing/rebalancing resources construct
  a Gantt chart and show weekly resource usage.
• Revise the Gantt chart and weekly resource usage
  assuming that we are time-constrained and can
  hire coders at 3K/week. Summarize your
  recommendation to your boss.
• If we are resource-constrained, redo the Gantt
  chart and resource usage to produce a feasible
  schedule. Summarize appropriately.

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Some Final Thoughts on Resources

• We may not have a pure time-constrained or
  resource constrained problem. A hybrid approach
  may be most appropriate.
• It may make sense to show management both
  extremes in order to triangulate to the best
  solution
• We have not explored revisiting activity
  dependencies, outsourcing tasks, doubling effort
  to do a task twice as fast (or halving effort to
  do twice as slow)
• In the next chapter we will look at one such
  possibility