Scheduling
- Scheduling is the process of fitting the work plan to
a time frame indicating the start and completion of each activity. It also
shows sequential relationships among various activities.
- Schedules are also prepared for construction
resources such as labor, materials, machinery and money required at
various stages of the work.
- The actual progress of each activity can be monitored
with reference to the planned program. If there are any delays, suitable
corrective action can be taken to speed up the work.
- The construction schedule is a tool that a contractor
uses to manage time and execute activities in a proper sequence.
- To prepare a construction schedule, the project is
divided into different activities or operations. The sequence of
operations can be decided after knowing their inter relationship as per
the construction method adopted. The construction schedule serves the
following purposes:
- Making available a time table showing the schedule
and sequence of each activity.
- Providing a schedule for monitoring the progress of
work and taking corrective measures, if required.
- Providing a means for establishing and maintaining
time goals and prioritizing activities.
Advantages of Scheduling
- For any important construction work, planning and
scheduling is indispinsible. Following are the advantages of scheduling:
- Alternative methods of construction can be examined
and the effect of likely constraints evaluated at the planning stage and
the most economical method is selected.
- It gives clear picture about the quantity and type
of materials needed at different stages of execution of work and the
duration of supply of material.
- The time of starting of each activity is known and
thus prior arrangements for adequate provision of resources such as men,
material and machines etc. for each stage of construction can be made.
- The resource utilization is optimized and the
available resources are directed to various activities to the best
advantage.
- The actual progress of each activity is monitored
with reference to the planned programme. If there is any delay in any
activity, the remedial measures are taken to speed it up, before it
causes difficulty in the other related activities.
- The inter-relationship of various activities and
their relative importance of each stage of construction is known. This
helps in fixing their priorities properly.
- The effect of any change, to such as modification
in the original plans, weather conditions etc. can be properly evaluated
and the programme of construction can be suitably amended.
- Total time to complete the project is known.
- The last and the most important advantage of scheduling is that the work may be executed in a most efficient way without wastage of time and any inputs, resulting in maximum possible economy. ;
Milestone scheduling
- Project milestone schedules contain such information
as:
- Project start date
- Project end date
- Other major milestones
Scheduling by Bar Charts
- The conventional method of scheduling used in the
construction industry is the bar chart. It is also known as Gantt
after Henry Gantt, who developed this technique around 1919.
- A bar chart consists of two co-ordinate axes, one
showing the time and the other showing jobs or activities to be performed.
- Each job is depicted in the form of horizontal line
or bar and the length of a bar indicates duration of the job or activity.
- In a project, some jobs are taken up concurrently and
some are required to be completed before others can begin.
Limitations /
Disadvantages of bar chart
- Limitations of bar chart are as follows:
a)
Interdependencies of activities
§ A
construction project consists of a large number of activities. The bar chart
does not show clearly the interdependencies among the various activities. This
is a major deficiency.
§ The
mere fact that two or more activities are scheduled to start at the same time,
it does not make them interdependent or completely independent.
b)
Project progress
§ A
conventional bar chart can not be used as an efficient control device because
it does not show the progress of work.
§ A
knowledge of the quantum of work completed or progress achieved is essential in
any project.
c)
Quantities of items of work
§ The bar chart depicts the time schedule
for various activities but it does not indicate the quantities of work.
§ The
bar chart may be improved by showing quantities of work against individual
items.
d)
Critical activities
§ Another
limitation of the bar chart is that it does not indicate critical activities
requiring careful attention of the construction team.
§ Knowledge
of critical activities is essential for rescheduling or accelerating the
project completion.
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