Calculating Activity Times & Float in Project Management, Lecture notes of Logic

Download Calculating Activity Times & Float in Project Management and more Lecture notes Logic in PDF only on Docsity!

Time Planning and Control

Activity on Node Network

(AON)

 Processes of Time Planning and Control

Processes of Time Planning

1. Visualize and define the activities.

2. Sequence the activities (Job Logic).

3. Estimate the activity duration.

4. Schedule the project or phase.

5. Allocate and balance resources.

Processes of Time Control

1. Compare target, planned and actual dates and update as necessary.

2. Control the time schedule with respect to changes

Each time-consuming activity is portrayed by a rectangular figure. The dependencies between activities are indicated by dependency lines (arrows) going from one activity to another. Each activity duration in terms of working days is shown in the upper, central part of the activity box. The principal advantage of the activity on node network is that it eliminates the need for dummies.  Activity on Node Notation Activity ID FF LS TF LF

Latest Starting Date Latest Finishing Date Total Float Duration Earliest Starting Date Earliest Finishing Date ES D EF FF Activity ID LS TF LF The left side of the activity box (node) is the start side, while the right side is the finish (end) side.  Activity Box Predecessor Successor Free Float Activity ID FF LS TF LF

A horizontal diagram format is the standard format. The general developing of a network is from start to finish, from project beginning on the left to project completion on the right. The sequential relationship of one activity to another is shown by the dependency lines between them. The length of the lines between activities has no significance. Arrowheads are not always shown on the dependency lines because of the obvious left to right flow of time. Dependency lines that go backward from one activity to another ( looping ) should not be used.  Crossovers occur when one dependency line must cross over another to satisfy job logic.  Network Format Activity ID FF LS TF LF

The activity list shown below represents the activities, the job logic and the activities’ durations of a small project. Draw an activity on node network to represent the project. Activity Depends on Duration (days) A B C E F D S R D R D R, S B, C None A, C A, C

 Example Activity ID FF LS TF LF

The purpose of network computations is to determine: The overall project completion time; and The time brackets within which each activity must be

accomplished (Activity Times ).

In activity on node network, all of the numbers associated with an activity are incorporated in the one node symbol for the activity, whereas the arrow symbols contain each activity’s data in the predecessor and successor nodes, as well as on the arrow itself or in a table. ES Duration EF Activity ID FF LS TF LF  Network Computations Activity ID FF LS TF LF

1. The "Early Start" (ES) or "Earliest Start" of an activity

is the earliest time that the activity can possibly start allowing for the time required to complete the preceding activities.

2. The "Early Finish" (EF) or "Earliest Finish" of an

activity is the earliest possible time that it can be completed and is determined by adding that activity's duration to its early start time.  EARLY ACTIVITY TIMES Activity ID FF LS TF LF

 Example Calculate the early activity times (ES and EF) and determine project time. D 4 A 4 C 8 E 7 B 5 F 3 END 0 S 2 R 9 0 4 4 4 8 12 12 12 14 21 21 21 28 26 26 29 29 29 EF = ES + D Largest EF Activity ID FF LS TF LF

3. The “Late Finish" (LF) or "Latest Finish" of an activity is

the very latest that it can finish and allow the entire project to be completed by a designated time or date.

4. The “Late Start” (LS) or "Latest Start" of an activity is the

latest possible time that it can be started if the project target completion date is to be met and is obtained by subtracting the activity's duration from its latest finish time.  LATE ACTIVITY TIMES Activity ID FF LS TF LF

 EXAMPL

E Calculate the late activity times (LS and LF).

D 4 A 4 C 8 E 7 B 5 F 3 END 0 S 2 R 9 0 4 4 4 8 12 12 12 14 21 21 21 28 26 26 29 29 29 LS = LF - D 0 8 4 4 12 12 20 12 22 21 22 21 29 26 26 29 29 29 Smallest LS Activity ID FF LS TF LF

 FLOAT Time  Float or leeway is a measure of the time available for a given activity above and beyond its estimated duration.  Two classifications of which are in general usage: Total Float and Free Float. Activity ID FF LS TF LF

 EXAMPLE Calculate Total Float for an activity.

Total float (TF) = LS - ES = LF - EF

D 4 A 4 C 8 E 7 B 5 F 3 END 0 S 2 R 9 0 4 4 4 8 12 12 12 14 21 21 21 28 26 26 29 29 29 0 8 4 4 12 12 20 12 22 21 22 21 29 26 26 29 29 0 29 0 0 0 0 (^0 ) 8 8 Activity ID FF LS TF LF

 Critical activity is quickly identified as one whose

two start times at the left of the activity box are equal.

Also equal are the two finish times at the right of the activity box.  The critical activities must form a continuous path

from project beginning to project end, this chain of

critical activities is called the "critical path".

 The critical path is the longest path in the network.  CRITICAL PATH Activity ID FF LS TF LF