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FS (Baseline) >> FF (updating)

13 replies [Last post]
Fri, 2007-06-08 02:05
ruy frank rosales
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I have been trying to analize the updates that I had been doing on the schedule that I am working on. And I have thought about this (see below). Correct me if I am wrong. I need insights as well.

Example 1: Construction = activity A
Pre-commissioning = activity B

•Most of the time in a baseline schedule A and B will be set in FS (finish to start relationship). If this is true, we can say that the finish date of A should affect the finish date of B.
•But during updating, at a certain date B can start even if A haven’t finished yet.
•As a result of the FS relationship, A’s finish date will no longer affect B’s finish date. Which is now, while updating, incoherent with the purpose of the baseline schedule.

Example 2: if A = 3 days duration
B = 3 days duration
So if A & B with FS relationship (0 days lag) = 6 days total duration
Then A & B with FF relationship (3 days lag = B) = 6 days total duration

If our goal is to determine the effect of each activity’s finish dates to the project finish date.

Query: Can I change all FS to FF with consideration to each activity’s baseline durations.

Reason: In order to monitor the effect of each activity’s updated finish dates to the project finish date.


Thanks and Best regards
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Replies

Mon, 2007-06-18 02:49
#1
A D
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Shaju,

Retained logic / progress override options has been discussed recently in the following post: plz check this.

http://www.planningplanet.com/forum/forum_post.asp?fid=&Cat=7&Top=33781

This will definitely help you out.

Anyway, it all started from to change all FS to FF with consideration to each activity’s baseline durations?

Cheers,

Raviraj A Bhedase
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Mon, 2007-06-18 02:26
#2
shaju varkey
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Dear Sridhar,

Let us go back to the core of the issue under discussion. I believe in retained logic option for scheduling, where the relationship is FS-0, the successor will not finish prior to predecessor finish.

Someone please correct me if I am wrong.

Regards
Shaju Varkey
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Sat, 2007-06-16 03:52
#3
Ponnaganti Sridhar
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Dear Raviraj Bhedase,

i enterly agree with the comments you had made, what i mean to say is the same to Anoon Iimo, but there is a small interpetion, i am not saying that resources numbers to be used to be limited ( i mean ristricted), but instead of that u have think the no.of resouces to be used to complete the activity in that particular duration depending on the productivy and the workable space avaliable, if they are ristricting, may be you to brake the activity or chose the alternativy method of implementing your plan, for which we have discuss with the consturction team(dept.,)and other project team members.

hello Anoon Iimos,

sorry no it is not my point of concern, if i realied you arrongantly pls forgive me, i just gave my view what i though, i don’t mean that u r some thing what u have mentioned, if i had ever such kind of words unknowing or knowingly pls for give

hai to all,

i just discussing what i know ,just like throughing a ball and keep the ball rollwing so that by this kind of dissuctions i am empower my knowledge, i am not if i wright or wrrong , so i request you all to correct me if i am wrrong and advice me what is wright

thank’s
Sridhar
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Tue, 2007-06-12 08:50
#4
Anoon Iimos
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Dear Ponnaganti,

Yes i also believe that sometimes there are contractual restrictions on the durations of major activities (meaning group of activities), but for specific activities (i mean task), then i would rather suggest that you reckon it in terms of productivity rates.

did i sound like stupid and arrogant? (sorry, but i’m really is!)
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Tue, 2007-06-12 06:09
#5
A D
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hi sridhar,

Many specifications require activities to be defined with durations less than a set number.

The intent of this requirement is to allow for better monitoring and control of the work described by the activity.

Typically, the reviewer is allowed to wave this requirement in the case of Hammocks or deliveries, etc.

Working from consultant side, we are quite aware of LONG TASK DURATIONS (Case "Hours": Odd = 40, Case "Days": Odd 20, Case "Weeks": Odd = 10, Case "Months": odd = 4.)

But, please don’t apply this test to resources or summaries.

Cheers,

Raviraj
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Tue, 2007-06-12 03:47
#6
Ponnaganti Sridhar
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Dear Anoon Iimos

what i mean to say is that if in the contract clause there is Restriction on the duration then u do??

so what i mean to say is then u have break down the activity furter.

ofcourse what u said about Produactivity is the main factor( the number of resourses) the get the duration of the activity

this is my view

if iam wrrong pls excuse me and please through your views on me

thankyou
Sridhar
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Tue, 2007-06-12 02:50
#7
Anoon Iimos
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you can never put a limit on the durations of activities, it will be dependent on the resource productivity rates. Unless you’re just putting Durations by Guess! (which is mostly done i guess!)
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Tue, 2007-06-12 02:38
#8
Ponnaganti Sridhar
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i completly agree with Bijaya Bajracharya.

i would like say one that there should be a limit on the duration of the activites ( min. & Max.) otherwise while updating activites (mostly construction activites) it would give a wag concept on the situation on the project

if iam wrrong pls suggest me

thankyou
P.Sridhar
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Mon, 2007-06-11 07:31
#9
Bijaya Bajracharya
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My suggestion is to replace FS relationship in such situation by SS and FF relationships. And this is real representation of situation as well. B cannot start until A has started. And B cannot finish until A has finished.
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Sat, 2007-06-09 06:22
#10
Anoon Iimos
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i suggest that you break your activities into bits and pieces if you’re using FS relationships to be realistic. Pre-commissioning of a certain activity shall never start until its predecessor activity is completed. You might create a very long schedule but that’s it. You got no choice if you wanted to be realistic.
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Fri, 2007-06-08 21:17
#11
ruy frank rosales
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But my schedule is already progressed or updated with actual starts and actual finishes.

My problem is when you have applied actual start to B then the finish date of A will no longer affect B in an FS relationship. It would seem like A can finish until the project finish date without effect to the whole project.

I can see your point once we want to change the duration.

I am wondering if someone have done this before to their schedule as a "what if" analysis to determine the effect of each activity’s finish dates to the project finish date.

Because it seems to me that maintaining FS relationships when actual starts had been applied gives me a hard time analyzing the floats. Sorry, I can’t even understand the floats now all the negatives and positives, yet the project finish date is steady as planned.
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Fri, 2007-06-08 07:46
#12
Gary Whitehead
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The issues you’ll have then is that the start of the commissioning task is nto linked to the construction. So if during update you’re requried to extend the duration of thecommissioning task (say due to resource constraints, your schedule could potentialy be telling you start commissioing before construction has even begun.

A better solution would be to use a Start-Start relationship with lag, though even this can give you problems as if construction takes longer than anticipated, you might see comissioning starting before enough of the construction work has been completed. Either way you have to monitor the lags you’re using on a regular basis to ensure they are still valid.

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Fri, 2007-06-08 05:57
#13
ruy frank rosales
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I guess I made a query which is just "generally" answerable by a simple... "yes".. or if you want why not..

Ok... seriously...

Is there a negative effect to what I stated above? will it make the schedule unrealistic instead? will it give me rather worse project finish dates?

Thanks
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