project scheduling - جامعة نزوى · aon versus aoa •aon networks are constructed without...

PROJECT SCHEDULING

PROJECT SCHEDULING

Next to the WBS analysis, the scheduling of work elements is the most important step in planning because it is the basis for allocating resources, estimating costs, and tracking project performance.

PROJECT SCHEDULING

Events and Milestones :

Project plans are similar to road maps: They show not only how to get to where you want to go, but how much progress you have made along the way. Along the way are signposts called events and milestones that show how far you have progressed.

PROJECT SCHEDULING

Events and milestones should not be confused with work packages, activities, or other kinds of tasks. A task is the actual work planned (or being done) and represents the process of doing something (such as driving a car to get somewhere); it consumes resources and time. An event signifies only a moment in time, usually the instant when

PROJECT SCHEDULING

something is started or finished (such as beginning a trip or arriving at the destination).

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Bar Chart Schedules The bar chart is graphically the simplest of the

scheduling methods. Most project people understand it, and it can be produced more quickly than any of other methods.

To quickly examine overall timing, owners, designers and construction professionals frequently use it in the planning stage of a project.

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2 0 4 10 6 8

3 1 5 7 9

Month

Month

Activity

Design house and

obtain financing

Lay foundation

Order and receive

materials

Build house

Select paint

Select carpet

Finish work

A Bar Chart

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Bar Chart Schedules Bar charts can also be used to report information

to people who are concerned about project but may not be involved in day-to-day management.

In summary:

1. Bar charts are excellent communicators of time-related project information.

2. They are quick and easy to develop and understood by most people.

Bar Chart Schedules

3. Their major limitation is that interpendencies among activities can not be shown.

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Network schedule

A Network schedule is a good tool for controlling field activities because it can be posted at the field office and update as the work proceeds. Most project people can find a specific task on the schedule and see due date.

Network schedule some times is called a critical path method (CPM) schedule.

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Network schedule

In Network schedules the activities are given a duration (in hours,days,weeks and so on), and they are connected by network diagrams.

A completed network thus defines activity interrelationship and durations, considers available resources, and assumes how the project will be pursued.

A network schedule can be viewed as a road map that, if followed, will bring the project to its desired destination.

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Network schedule

Network schedules two forms:

1) activity on arrow notation

2) activity on node notation (precedence notation).

In activity on arrow notation, the work or activity is shown on the arrows, which are connected by nodes. In precedence notation, the work occurs on the nodes, which are connected by arrows.

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Mobilize

Lay out

footings Excavate

footings

Forms and

concrete

Erect

steel

Procure formwork

Procure steel

Activity on arrow notation

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Mobilize Lay out

footings

Excavate

footings

Forms and

concrete

Erect

steel

Procure

formwork

Procure

Steel

Activity on node notation

Network schedule

• The two common methods for constructing network diagrams are called activity on-node (AON) and activity-on-arrow (AOA). Both were developed independently during the late 1950s.

Example:-

AON Diagram

Dummy Activities

A dummy activity is used to illustrate precedence relationships in AOA networks. It serves only as a “connector,” and represents neither work nor time.

AOA Diagram

AON versus AOA

• AON networks are constructed without use of dummies they are simpler and easier to construct.

• Because AOA diagrams use line segments (the

arrows) to represent the flow of work and time, it is easy to construct schedules that are similar in appearance to Gantt charts but incorporate the advantages of networks.

• Most project software packages create AOA networks that look similar to Gantt charts.

THE CRITICAL PATH

• The major use of networks is for scheduling—determining how long the project will take (the expected project duration) and when each activity should be scheduled.

• The longest path from the origin node to the terminal node is called the critical path; this gives the expected project duration.

There are two paths from the origin node to the terminal node. The shorter path J-L-Q-W-X is 18 weeks long; the longer path J-M-V-Y-W-X is 26 weeks