Civil Engineering Reference
In-Depth Information
Actual duration
=
7days
Remaining duration
=
11 days
(
assuming the end of activity A
+
1day
)
Using the DML equation:
AD
B
(
1
−
PC
A
)+
L
PC
A
RD
B
=[
7
(
1
−
0
RD
B
≥
.
70
)+]∕
0
.
70
=
4
.
43
,
say 5 days
This result sounds like a violation of the FF relationship with activity
A, which puts the remaining duration of activity B at 11 days. In reality,
the remaining duration of activity A will be, most likely, a lot less than 10
days. Assuming linear production: If activity A reached 70% completion
in 10 days, it could reach 100% in 10
∗(
100
%∕
70
%) =
14
.
29 days,
29 days, which is slightly less than
the 4.43 days calculated by the DML equation as the minimum for
RD
B
.
Practically speaking,
RD
A
and
RD
B
can be 4 and 5 or 5 and 6 days,
respectively.
2. Repeat step 1, assuming that activity B started as scheduled, that is,
at the end of day 5.
that is, the remaining duration
=
4
.
Activity B (Shingles):
Actual duration
=
5days
Remaining duration
=
11 days
(
Assuming the end of activity A
+
1day
)
Using the DML equation:
RD
B
≥
[
5
(
1
−
0
.
70
)+
1
]∕
0
.
70
=
3
.
6
,
say 4 days
The same argument as previously given applies:
RD
A
and
RD
B
will
most likely be 4 and 5 days, respectively.
CONCLUSION
The DML relationship is a new and potentially useful concept in project scheduling.
It should be used mainly for a situation involving overlapping activities when the pre-
decessor has to stay ahead of the successor by a certain margin from start to finish.
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