Bar (Gantt) Charts - Construction Project Scheduling and Control - page 20

With the advent of logic networks and the critical path method (CPM) and the
evolution of powerful computers and software, bar charts have not perished or lost
importance. Instead, they have evolved from a scheduling technique to a report-
ing tool, which that has made them more valuable and popular. This is explained
in Chapters 3 and 4.
Tip Box 2.1
The most important advantage of bar charts is their simplicity. Whatever you do, don't
lose this advantage.
DISADVANTAGES OF BAR CHARTS
The main disadvantage of bar charts is their lack of logical representation (relation-
ships); for example, why an activity started on a certain date (bar charts don't reveal
the answer). The reason can be a logical relationship, a resource constraint, or a sub-
jective decision by the project manager. Although some software programmers try to
depict logical relationships on bar charts, the result is not always clear. The logic lines
get tangled, and unlike networks, bar charts do not allow the length of the bars to
be subjectively changed or the bars to be moved around to make the chart look or
read better.
Another limitation, rather than a disadvantage, of bar charts is the size and com-
plexity of projects. Bar charts may not be practical for projects with a large number of
activities, unless you use them in two ways:
1. You show a subset of the work activities to maintain the simplicity of the chart.
For example, the general contractor can produce bar charts for activities to be
performed during only a certain period (two weeks, for example), for critical
activities (activities that cannot be delayed or the entire project would be
delayed; a full definition and discussion follows in Chapter 4) only, for activities
in a certain section of the project, or for activities under a certain subcontractor.
2. You show summary/rolled up bars (each bar represents a group of activities
combined on the basis of a certain criterion, such as department, major com-
ponent, or responsibility). This can be done during the early planning phase,
when details are not available (see, for example, Figure 2.7) and when you are
reporting the information to high-level management.
New technology (computers, software, printers, plotters, etc.) has minimized or
even eliminated some of the disadvantages of bar charts by enabling the user to orga-
nize, filter, roll up, summarize, or do almost anything to customize bar charts. We will
discuss reporting and presentation further in Chapter 10.