Chapter 3 Project Management. Projects are typically characterized as: –one-time, large scale...
-
Upload
jarvis-dowers -
Category
Documents
-
view
219 -
download
2
Transcript of Chapter 3 Project Management. Projects are typically characterized as: –one-time, large scale...
Chapter 3
Project Management
Project Management
Projects are typically characterized as:– one-time, large scale operations– consuming large amount of resources– requiring a long time to complete– a complex set of many activities
3 Important Project Management Functions:– Planning – determine what needs to be done– Scheduling – decide when to do activities– Controlling – see that it’s done right
PERT/CPM project management technique(Program Evaluation & Review Technique)/(Critical Path Method)
• Inputs– list of activities– precedence relationships– activity durations
• Outputs– project duration– critical activities– slack for each activity
1 2Excavate
& pour footings
Pour foundation
Install drains
Project Network for House Construction
3
6
7
4
8
9
5
10
11
12
16
1813
1715
14
Install roughelectrical & plumbing
Pourbasement
floorInstall
cooling &heating
Erectframe & roof
Laybrickwork
Laystormdrains
Installdrywall
Layflooring
Installfinished
plumbing
Installkitchen
equipmentPaint
Finishroof
Installroof
drainage
Finishgrading
Finishfloors
Pourwalks;
Landscape
Finishelectrical
work
Finishcarpeting
CPMA project has the following activities and precedence
relationships:
Immediate Immediate Predecessor Predecessor
Activity Activities Activity Activitiesa -- f c,eb a g bc a h b,dd a i b,de b j f,g,h
Construct a CPM network for the project using:1.) Activity on arrow2.) Activity on node
Activity on Arrow(Initial Network)
Activity on Arrow(Final Network)
a
b
c
d
e
f
g
hi
j
Activity on Node
Critical Path
path any route along the network from start to finish
Critical Path path with the longest total duration
This is the shortest time the project can be completed.
Critical Activity an activity on the critical path
*If a critical activity is delayed, the entire project will be delayed. Close attention must be given to critical activities to prevent project delay. There may be more than one critical path.
To find critical path: (brute force approach)
1. identify all possible paths from start to finish
2. sum up durations for each path
3. largest total indicates critical path
1
2 6
4 7
53
b = 2
d = 4
g = 9
h = 9
f = 8c = 5
a = 6
k = 6
j = 7
i = 4
e = 3
Slack Times
Earliest Start (ES) – the earliest time an activity can startES = largest EF of all immediate predecessors
Earliest Finish (EF) – the earliest time an activity can finishEF = ES + activity duration
Latest Finish (LF) – the latest time an activity can finishwithout delaying the project
LF = smallest LS of all immediate followers
Latest Start (LS) – the latest time an activity can start without delaying the project
LS = LF – activity duration
Slack Times
Slack how much an activity can be delayed
without delaying the entire project
Slack = LF – EF or Slack = LS – ES
Slack
EF LF
ES LS
c = 10
g = 12
f = 1
7b =15
a = 10 e = 15
i = 7
d = 20
h = 9
b = 4
d = 5
h = 5
i = 3
c = 5
a = 5g = 4
j = 6
e = 5
f = 6
Input Table for Microsoft Project(Example 10.1, page 387)
Gantt Chart for Microsoft Project(Example 10.1, page 387)
Project Network for Microsoft Project(Example 10.1, page 387)
Activity Crashing(Time-Cost Tradeoffs)
An activity can be performed in less time than normal, but it costs more.
Problem: If project needs to be completed earlier than normal, which activity durations should be decreased so as to minimize additional costs?
Guidelines:• Only crash critical activities• Crash activities one day at a time• Crash critical activity with lowest crashing cost per day
first• Multiple critical paths must all be crashed by one day
Activity Crashing Example
Crash project as much as possible.
Activity DurationCrashedDuration
ActivityCost
CrashedCost
CrashingCost/day
a 3 2 40 45
b 4 3 50 54
c 8 5 50 68
d 5 4 30 33
c = 8 d = 5
b = 4a = 3
Minimum duration = 9 days; Total additional cost = $30
Program Evaluation & Review Technique(PERT)
3 duration time estimates
– optimistic (to), most likely (tm), pessimistic (tp)
Activity duration:
mean te = (to + 4tm + tp) / 6
variance Vt = [(tp – to) / 6]2
Path duration:
mean of path duration = T = Σ te
variance of path duration = σ2 = Σ Vt
X = T ± Zσpath
Z is number of standard deviations that X is from the mean.
Example: If the mean duration of the critical path is 55 days and the variance of this path is 16, what is the longest the project should take using a 95% confidence level?
probabilityof being late
.05
actualproject
duration
T55
X
Zσcp
PERT Example
If the expected duration of a project is 40 days and the variance of the critical path is 9 days, what is the probability that the project will complete in less than 45 days?
in more than 35 days?
in less than 35 days?
in between 35 and 45 days?
probabilityof being late
actualproject
duration
T40
45
Zσcp
PERT Example
The expected duration of a project is 200 days, and the standard deviation of the critical path is 10 days. Predict a completion time that you are 90% sure you can meet.