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Relationship between RD & TF

6 replies [Last post]
Mon, 2006-01-09 14:52
Kashyap Mothali
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I always thought that the Remaining Duration "RD" and the Total Float "TF" values are inversely proportional i.e., when the RD becomes less, the Total Float either remains the same or improves.

However, I have a Contractor’s schedule, which reflects just the opposite on a particular activity! When I increase the RD and the OD on this activity (due to extra work), the Total Float value also seems to improve. I don’t remember having seen this occur before. Could anyone please explain why this is happenning?

Not to mention that there are numerous lags along with all four types of relationships in this schedule (SS, SF, FS & FF).

Regards,

Kashyap Mothali
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Replies

Sun, 2006-01-15 15:19
#1
yousif alaubidi
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Dear Ronald Winter

Thanks for your information

with best wishes
15/1/2006
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Sat, 2006-01-14 21:07
#2
Ronald Winter
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You need to begin to look past the inputs versus the outputs and see what is actually happening. What are the work day numbers? Calculate early start date, add remaining duration, subtract one and calculate early finish. Translate that into the actual date using the current calendar. If this is too much of a bother, then use MS Project and just tell the Owner, “that’s what the software says it should be.”

Stop trying to come up with general rules to guide you in CPM when the entire process is complex and not amenable to general rules. Good luck!
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Fri, 2006-01-13 08:39
#3
Kashyap Mothali
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Thanks for the feedback guys, but my problem is this.

When I increase the RD on one activity, it’s the same activity that shows an impovement in the total float....unlike the example that Joao elicited.

Kashyap
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Thu, 2006-01-12 01:57
#4
Charleston-Joseph...
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Hello Kahyap,

Now you know that what you thought is not really what the way P3 is acting. This is not the only fundamental in Critical Path scheduling that will give you surprises. There are a lot of them in P3.

If you are doing forensic analysis of the schedule, you may end up confuse. This is because of the relationships that links activities, just complicated.

In this situation, I would suggest that you just do a simple forensic analysis of impacted schedule taking into consideration one event at a time. In this way you will be able to come up with claim entitlement considering only one event. As you evaluated more events, you will arrive at the most advantageous events that will mazimize your claim entitlement.

I hope this will help you, as a start. You can always come back to PP for assistance in the event you got bog down again.

Cheers,

Charlie

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Tue, 2006-01-10 04:40
#5
Joao Ribeiro
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Correction:
TF for T3 goes from 10d to 15d.
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Tue, 2006-01-10 04:34
#6
Joao Ribeiro
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Can you be more specific? Namely, what are the relationships?
It can happen with SF. Eg:

T1 5d
T2 10d
T3 5d

T1 - FS - T2
T2 - SF - T3

T1 TF=0; T2 TF=0; T3 TF=5

if RD T2 changes from 10d to 15d, TF of T3 goes from 5d to 10d. The example considers PCT of all task 0%.
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