Resource analysis
Project management
(lecture + seminar)
Introduction
• Sometimes one or more resources (especially
skilled workers) are equally or more
important than time. According to priority,
there are:
– time-limited and
– resource-limited
projects. Priority can change over time but it is
not wise to have double priorities.
• Basic tools came from production engineering:
loading (resource allocation)
Resources
• Definition: anything that is scarce and required for any
activity in the project. Resources are constraints for the
project.
• Resources can be:
– Non-storable: has to be renewed for each period
e.g. work
– Storable: depleted only by usage (remains available if not used)
e.g. money
• The most common resource typology, the 4Ms:
–
–
–
–
–
Men
Machines
Money (cost)
Material
Other
Loading (resource allocation)
• The assignment of work to an worker, machine
or unit (generally: to a workstation) in time.
• A workstation can be:
– underloaded (load < capacity)
– fully loaded (load = capacity)
– overloaded (load > capacity)
• Fully loading is nearly impossible to reach except
in flow production.
• Underloading is the most common, because it
respects time. Overloading leads to be late.
Defining resources for projects
• SOW
• WBS
• Task list
– Resource needs given in resource-hours
(e.g. man-hour, machine-hour)
– Two forms of resource specification:
• Rate-constant (can be changed to a constant
function/pattern): constant usage rate defines the
duration, too
• Total constant: to finish the activity
What to do with non-linear
duration-resource functions?
• Use a computer
• Focus on quasi-linear parts of the functions
Capacity
• Be realistic:
– Usual efficiency
– Estimated absenteeism, sickness, holidays
– Existing commitments
– Ancillary tasks and their resource needs
– Any additional constraints (like methodology) and
limitations (like work contracts)
• Also calculate with the possibilities
(cost, time, trade-offs) to increase capacity
Optimum seeking procedures
• Constraints:
– Resource-limited projects
– Time-limited projects
– Resource-limited AND time-limited projects
(question of priority)
• Methods:
– Linear programming
– Levelling
– Allocation
– Smoothing
Linear programming
• Successful only for small networks
(up to about 200 activities)
• Need for precise data
Levelling (simplest technique)
• Need for a previously produced starting
schedule.
• Attempts to level out peaks and valleys in
resource requirements by rescheduling some
activities.
• Difficulty of interactions between activities.
Allocation (for resource limited cases)
• Allocation resources
• ‘Splitting’ an activity: stopping an activity, which
is currently in progress, by the removal of its
resources for use on an activity of higher priority.
• Two procedures for allocation:
– Serial: if only a few activities are splitable
– Parallel: if many activities are splitable; more
complicated method that needs more time and data
Allocation when resources are
limited
• Serial procedure:
1.
2.
All activities in the project are ranked using constant priority rule.
The most frequently used rule: ascending order of the LSTs with a
tiebreaker of the ascending order of total floats (a kind of ‘urgency’).
Activities are scheduled in the above order at the earliest possible point
in time consistent with the availability of resources and the precedence
requirements.
• Step-by-step process:
–
–
–
Draw the network diagram for the logical connections
Compute the activity times and total floats
Plot a Gantt or time-scaled network in tandem with a resourcehistogram
Allocation when resources are
limited
• Parallel procedure:
Activities are considered sequentially (sub-lists). Unscheduled
activities are retained and ranked in the next period with new
activities.
d
a
i
e
l
START
b
f
j
g
c
h
k
FINISH
The time-limited case
• Balancing the S-curve with milestones:
Forcing early activities to start sooner
Smoothing (time limited)
• Aim is to produce a feasible schedule within the
time constraints & provide as smooth a resource
requirement profile as possible.
• Informational needs of smoothing:
– Start time and timeframe (TPT or deadline)
– Priority order of the resources required
• Prioritising activities and selecting them in order
for scheduling (critical activities have supreme
priority).
• Finding the best place for the activity (placing).
• Repeat the process with the next activity.
Prioritising activities
Considerables:
• Resource type(s) and importance
• Total work content (resource units per time
multiplied with the duration for all resources
used on the activity)
• Available float
Formula if no initial scheduling exists:
(Total work content) / (Float remaining)
In descending order (greatest first).
Placing
• The best position is the one that gives the
lowest usage increase in the time span of
the activity.
• Two ways of finding this position:
– Visual
– Sum of squares:
• Calculate the sum of squared resource needs of
each period within the questionable time frame
(between the ES and LF time of the given activity)
for every possible positioning
• Choose the position with the lowest value
seminar
Defining resources for projects 2
•
•
•
•
•
•
SOW
WBS
Task list
Logical connections (PNT)
Gantt chart and histogram
Levelling
Using the bar chart
• Set up and analyse the network
– Assign the resource data to the activities
• Draw the Gantt chart
– Aggregate each resource time period by time
period throughout the total project
• Cumulating (Summation or S Curve):
• Use levelling the load for optimization
Network with single resource data
0
2
0
0
0
0
0
0
0
0
2
a
(1)
2
2
0
0
5
5
5
b
(4)
5
10
c
(3)
8
10
3
5
0
10
0
2
START (0)
0
2
0
5
3
7
d
(2)
5
10
10
10
0
13
e
(1)
3
13
0
13
0
13
FINISH (0)
13
0
13
Aggregation with a bar chart
(single resource, earliest start)
activity
1
2
3
4
5
a
1
1
b
4
4
6
7
8
9
10
4
4
4
c
3
3
3
3
3
3
3
3
d
2
2
2
2
2
e
11
12
13
1
1
1
Res. aggr.
5
5
9
9
9
5
5
3
3
3
1
1
1
Cum. res.
5
10
19
28
37
42
47
50
53
56
57
58
59
1
2
3
4
5
6
7
8
9
10
11
12
13
Resource units
11
10
9
8
7
6
5
4
3
2
1
Time
Aggregation with a bar chart
(single resource, latest start)
activity
1
2
a
1
1
3
4
5
b
c
3
3
3
d
6
7
8
9
10
4
4
4
4
4
3
3
3
3
3
2
2
2
2
2
e
11
12
13
1
1
1
Res. aggr.
1
1
3
3
3
9
9
9
9
9
1
1
1
Cum. res.
1
2
5
8
11
20
29
38
47
56
57
58
59
1
2
3
4
5
6
7
8
9
10
11
12
13
Resource units
11
10
9
8
7
6
5
4
3
2
1
Time
The S Curve analysis
• The minimum slope level is the less ‘critical’
from the viewpoint of availability
S Curve of the example
70
60
50
40
ES
LS
30
smoothest
20
10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Scheduling with constraints
Three approaches:
• Allocation: Activities are scheduled so that an
initially defined limit of resources or time is
not exceeded.
• Levelling: A previously generated schedule
must be given. Then it levels out the peaks
and troughs without changing the TPT.
• Smoothing: A start time, a TPT and resource
priorities are required.
Other possibilities
• Alternative resources
• Alternative methods
• Alternative sequences
(if there is no technical dependency)
Levelling the load
• We must have a starting allocation of activities over
time and a resource constraint (previous example).
Resource units
11
10
9
8
7
6
5
4
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
Time
• Trying to keep the original TPT unchanged
means that critical activities should not be
moved. Thus try to move activities with free
float.
13
Solution
• There are only 2 activities with free float: b & d
• Which one to move and to where?
• Moving activity d 3 days in advance is
eliminating the peak.
Resource units
11
10
9
8
7
6
5
4
3
2
1
1
2
3
4
5
6
7
Time
8
9
10
11
12
13
activity
1
2
3
4
5
a
1
1
b
4
4
6
7
8
9
10
4
4
4
c
3
3
3
3
3
3
3
3
d
-
-
-
2
2
2
2
2
e
11
12
13
1
1
1
Res. aggr.
5
5
7
7
7
5
5
5
5
5
1
1
1
Cum. res.
5
10
17
24
31
36
41
46
51
56
57
58
59
S Curve
70
60
50
ES
40
LS
smoothest
30
leveled
20
10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Effect of levelling
• New „activity”: waiting for the resource
(it is a lag, not a true activity)
0
2
0
0
0
0
0
0
0
0
2
a
(1)
2
2
0
0
0
0
5
b
(4)
5
5
c
(3)
8
10
0
0
0
10
0
5
START (0)
0
2
0
5
0
10
d
(2)
5
10
10
10
0
13
e
(1)
3
13
0
13
0
13
FINISH (0)
13
0
• Changes: new precedence relationship, floats,
late start and finish times
13
Network with single resource data
0
2
0
0
0
0
0
0
0
0
2
a
(2)
2
2
0
0
5
5
5
b
(4)
5
10
• Resource limit: 5
c
(3)
8
10
3
5
0
10
0
2
START (0)
0
2
0
5
3
7
d
(2)
5
10
10
10
0
13
e
(1)
3
13
0
13
0
13
FINISH (0)
13
0
13
Network with multiple resource
data
0
0
0
0
0
0
0
2
2
0
8
2
0
10
2
3
0
10
10
3
START (0)
0
0
c (3A)
2
a (2A)
0
2
0
13
e (3B)
10
3
13
13
7
5
0
5
5
5
5
5
10
5
b (4B)
5
5
10
• Resource limits: 5A, 5B
0
13
FINISH (0)
d (2B)
0
0
10
5
8
f
(3A)
3
13
13
0
13
Reading
• Lockyer – Gordon (2005): Chapter 17 & 18
Thanks for your attention