7 Scheduling Resources and Costs

SCHEDULING RESOURCES AND COSTS

The Resource ProblemResources and Priorities

Project network times are not a schedule until resources have been assigned.

o The implicit assumption is that resources will be available in the required amounts when needed.

o Adding new projects requires making realistic judgments of resource availability and project durations.

Types of Project ConstraintsTechnical or Logic Constraints

Constraints related to the networked sequence in which project activities must occur

Resource ConstraintsThe absence, shortage, or unique interrelationship and interaction characteristics of resources that require a particular sequencing of project activities

Constraint Examples

Kinds of Resource ConstraintsPeople

Materials

Equipment

Working Capital

Resource Allocation ProblemA shortcoming of most scheduling procedures is that they do not address the issues of resource utilization and availability.

Scheduling procedures tend to focus on time rather than physical resources.

Classification of a Scheduling ProblemClassification 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 willsimply delay the project.

Resource Allocation MethodsLimiting Assumptions

Splitting activities is not allowed—once 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) doesn’t 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 toover-restrictive scheduling or inability to react to personnel changes.

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.

Resource LoadingResource loading describes the amounts of individual resources an existing schedule requires during specific time periods.

The loads (requirements) of each resource type are listed as a function of time period.

Resource loading gives a general understanding of the demands a project or set of projects will make on a firm’s resources.

The project manager must be aware of the flows of usage for eachinput resource throughout the life of the project.

It is the project manager’s responsibility to ensure that the required resources, in the required amounts, are available when and wherethey are needed.

Resource Leveling (Smoothing)Resource leveling aims to minimize the period-by-period variations in resource loading by shifting tasks within their slack allowances.The purpose is to create a smoother distribution of resource usage.Resource leveling, referred to as resource smoothing, has two objectives:

To determine the resource requirements so that they will be available at the right time,To allow each activity to be scheduled with the smoothest possible transition across usage levels.

Resource Leveling (Smoothing)

Resource management is a multivariate, combinatorial problem, i.e. multiple solutions with many variables, the mathematically optimal solution may be difficult or infeasible.

More common approach to analyzing resource leveling problems is to apply some resource leveling heuristics.

Resource Leveling Heuristics

Prioritizing resource allocation include applying resources to activities:

with the smallest amount of slackwith the smallest durationthat start earliestwith the most successor tasksrequiring the most resources

Resource Leveling StepsCreate a project activity network diagramCreate a table showing the resources required for each activity, durations, and the total float availableDevelop a time-phased resource loading tableIdentify any resource conflicts and begin to smooth the loading table using one or more heuristics

Resource Loading ChartAnother way to create a visual diagram of resource management problem is to use resource-loading charts.Resource conflicts can be seen in the resource-loading charts.They are used to display the amount of resources required as a function of time on a graph.Each activity’s resource requirements are represented as a block (resource requirement over time).

Resource Loading ChartResource limit is set at 8 hourly units per day.Display the amount of resources required as a function of

time.

0 A 4 Res = 6

4 B 5 Res = 2

5 D 9 Res = 7

9 E 11 Res = 3

4 C 7 Res = 2

11 F 12 Res = 6

1. Start with a network diagram

Resource Loading ChartActivity Resource Duration ES Slack LF

A 6 4 0 0 4B 2 1 4 0 5C 2 3 4 4 11D 7 4 5 0 9E 3 2 9 0 11F 6 1 11 0 12

2. Produce a table that shows the duration, early start, late finish, slack, and resource(s) required for each activity.

Resource Loading Chart

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

Pre and Post Smoothing

Resource Allocation MethodsResource Demand Leveling Techniques for Time-Constrained Projects

Advantageso Peak resource demands are reduced.

o Resources over the life of the project are reduced.

o Fluctuation in resource demand is minimized.

Disadvantageso Loss of flexibility that occurs from reducing slack

o Increases in the criticality of all activities

…Are projects that involve resources that are limited in quantity or by their availabilityScheduling of activities through use of heuristics (rules-of-thumb), according to the following priorities.o Note- Heuristics do not guarantee optimal solutions, but they help

in finding a decent solution quicklyStart from beginning of project time and, when resources used exceed the resources available, retain activities first by:

1. Minimum slack2. Smallest (least) duration 3. 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.

Resource-Constrained Projects

Example: Resource Constrained Project

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

Example of Resource-Constrained Scheduling

Prior to Resource Balancing…

ES resource load chart (with slack in gray)ES resource load chart (with slack in gray)ES resource load chart (with slack in gray)

Start Shifting Activities Later to Satisfy Resource Availability

Resource-constrained schedule through period 5–6ResourceResource--constrained schedule through period 5constrained schedule through period 5––66

2 2 2 2 2 2

1 1

1 1 1 1

1 1

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….)

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

Resource Load Now Feasible

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

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

Example in MS-ProjectGo to… tools: level resources1. For resource-constrained leveling, use the default settings2. 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

(Another) Computer Demonstration ofResource-Constrained Scheduling

EMR ProjectThe development of a handheld electronic medical reference guide to be used by emergency medical technicians and paramedics

ProblemThere are only eight design engineers who can be assigned to the project due to a shortage of design engineers and commitments to other projects.

EMRProject: NetworkView of

Schedule before

Resources Leveled

This is the illustration from the book,which has 2 grievous errors-Can anyone spot them?

EMR Project Prior to Leveling Resources

Time Constrained: Leveling Within SlackWe reduce the need for some overtime…but still have a large peak at the end, so this is probably not acceptable

Leveling by Allowing the Project Duration to Expand

If we take MS Project’s 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 3/20Resource usage between 5 to 8 engineersCan insert “leveling delay” column in schedule view to see the shifts

Even manually make them without relying on MS algorithms.

The Impacts of Resource-Constrained Scheduling

Reduces delay but reduces flexibilityIncreases sensitivity of the network Increases scheduling complexityCan break the sequence of eventsMay cause parallel activities to become sequential and change the critical path

Splitting/Multi-taskingA 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 experts would argue this is not a good approach.

Assigning Project WorkFactors to Consider:

Don’t 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.

Multiproject Resource Schedules

Multiproject Scheduling ProblemsOverall project slippage

o Delay on one project creates delays for other projects.

Inefficient resource applicationo The peaks and valleys of resource demands create

scheduling problems and delays for projects.

Resource bottleneckso Shortages of critical resources required for multiple

projects cause delays and schedule extensions.

Multiproject Resource SchedulesManaging 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.

o 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.

Some Final Thoughts on ResourcesWe 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)

View Resources in MS ProjectIn “Resource Graph” can see the overageSet resource availability via view: resource sheet

Defaults to increments of 50% but you can manually type in different amount