Gantt chart is the graphical representation of materials and production schedules for various activities of the project.
It is a project management tool.
What is the Gantt Chart and why it is important?
Mr Henry, L. Gantt evolved a chart of planning and controlling the production of ordinate factories, which is known as a Gantt chart
or Bar chart.
The bar chart consists of two coordinates.
- Horizontal coordinates
- Vertical coordinates
The horizontal ordinate represents the duration required for completion of the activities
The vertical abscissa represents the respective jobs to be performed.
The length of the bar shows the time taken by the job or activity for its completion.
The duration of the activities represents from left to right.
Each bar is divided longitudinally into two portions.
- Top portion
- Bottom portion
The top portion indicates the process of completion of the activities
The bottom portion indicates the duration of the activity.
Importance and Advantages of Gantt Chart
The following are the main advantages of the bar chart.
- Easy to draw and to understand
- A person without experience can easily make the chart.
- Very easy to make the comparison of progress of activities and the original schedule.
- Using this chart can know the resources requirement time for each activity.
- If required we can modify the chart very easily.
- Using this chart it is easy to make inter-relationship between various activities.
Limitations of the Gantt chart, Project management tool
The following are the limitations of the gantt chart
- Interdependencies of activities
- Project progress
1. Interdependencies of activities
A project can have a large number of activities which can start at different intervals of time.
The bar charts fail to indicate clearly the interdependencies among such activities.
Simply drawing the bars of the activities, parallel to each other, does not always make them related or interdependent or completely dependent.
In a concreting operation, the following activities are involved
- Mixing the ingredients
- Transportation of concrete
- Placing of concrete
- Compaction of the concrete
- Curing of the concrete
These activities have to run in proper sequence serially
One activity must be completed before its succeeding activity can start.
On a bar chart, the bars representing these activities are not allowed to overlap.
Example 2 :
Another drawback of a bar chart is that two parallel bars need not always represent independent activities.
Let us image the project have the following activities whose duration are given below
- Excavation of foundation – 24 days
- Erection of the shuttering – 14 days
- Placing of concrete – 10 days
For the execution of these activities in strict sequence,
The total time required for the completion of the project = 24 + 14 + 10 = 48 days
But, in this case, one need not wait for complete excavation of the foundation for the starting of the next activity of the creation of the shuttering.
Say, after 12 days of excavation of foundation, erection of shuttering of sideboards may be started.
Similarly, after 6 days of erection of shuttering, the concreting activity can be started.
According to the above durations,
The timeline for Erection of shuttering of sidebars will be 13th day to 26th day.
The timeline for the placing of concrete will be 18th day to 28th day.
According to above, Gantt chart schedule to time schedule,
Shuttering still needs 2 days after excavation work is over.
Similarly, placing of concrete will have 2 days work after the erection of shuttering.
If due to some unforeseen reasons, excavation work or erection of shuttering is delayed by one day,
how this delay will affect the subsequent activities cannot be indicated by the bar chart.
A bar does not indicate the progress of the project,
So this chart cannot be used as a control device.
In every project, it is essentially required to have up to date knowledge of the amount of work in progress or work completed.
The changes in plans of a large project may be suitably made on a bar chart.
The most important limitation of the bar chart is that it cannot affect the uncertainties or tolerances in the timeline schedules of the various activities of the project.
If uncertain activities are found, they can not be forecasted with exactness using this bar chart.
In modern projects, programme rescheduling of activities necessary part of the project but this cannot be reflected on a bar chart.
Critical Path method|Project management