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Finish-to-Finish driving relationship.

9 replies [Last post]
Mina Arsal
User offline. Last seen 3 years 32 weeks ago. Offline
Joined: 15 Sep 2008
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This is my first project I am using the following technique. I started to call it "Time Frame Scheduling", simply I started to open time frame for the activities not an exact duration for each activity.

First I start to open a time frame for a specific activity (A1) which identify the possibility of starting the activity then link it with its successor with FF lag relation ship with another time frame for the successor activity (A2) in which I calculate the duration of A2 as follow: after which duration from starting A1 I can start A2.

This technique enables me to have an early start for the A2 and at the same time I am not restricted to specific duration as A2 will always be in progress as long as A1 is not finished.

When I am updating schedule I start tracing the FF relationship is still driving or the long duration of A2 became the driving. If so, I start reducing the time frame of A2.

I would like to hear from you about this technique.

Replies

Carlos Arana
User offline. Last seen 1 year 43 weeks ago. Offline
Joined: 6 Jun 2009
Posts: 178
Mina:

Many of the discussion in this forum is around Critical Path Method (CPM), as it is a proven, mathematical technique for planning. These are the basics of CPM:
http://www.youtube.com/watch?v=zoBv45v_AQY

What is the difference between your "time frame" and floats as defined in CPM? Remember: lags are not the same as floats.

Maybe your question is wrong, instead of asking "after which duration from starting A1 I can start A2?", you should ask "At what point of A1 completion can I start A2?", then divide A1 in two activities: one to the point from where you can start A2, and other from that point up to A1 completion.

Still, looks like your approach to planning has been thought by someone else before, maybe you should try Liquid Planner, it looks closer to what you are trying to achieve.
http://www.liquidplanner.com/

Regards.
Scarllet Pimpernel
User offline. Last seen 9 years 3 days ago. Offline
Joined: 19 Jul 2009
Posts: 152
Hello Mina,

Why bother? After all whar you are generating is not a proper CPM logic.

I tell you what? the best approach now is to use partnership contract.

In partnership contract, the planning is so rubbish that no one is accountable: Contractor, Client, Consultant because the basic tenet of partnership contract is nobody is accountable since we are all partners, no one should be penalized.

In this situation, the best planning idiots can always fit. For a 4 years duration contract, which cost around 3 billion USD, most activities (95%) in the baseline schedule will have a total float of 1250 calendar days.

Can you imaging a 4 year contract, with budget in the area of 3 billion USD, with 95 percent of the activities having 1250 calendar days float. This particular projects will be a resting place or vacation place for highly paid (around 50,000 AED per month tax free) idiotics planners.

I’m speaking based on facts.

So whatever drive your activities is irrelevant, just make money.

thank you,
Scarlett
Mike Testro
User offline. Last seen 54 min 25 sec ago. Offline
Joined: 14 Dec 2005
Posts: 4403
Hi Mina

What is the difference between a duration and a time frame?

Have you seen what happens whent you update progress and the lead lag links are still hanging out?

I look forward to your method being universally adopted - my business will have to expand to keep up with all the delay claims.

Best regards

Mike Testro
Anoon Iimos
User offline. Last seen 1 year 11 weeks ago. Offline
Joined: 22 Sep 2006
Posts: 1416
Mina,

I believe you got a problem with your engineering (but who doesn’t anyway?).For me, all relationships are theoretical (who said that it’s not?).

Are you looking for timeframe for unsure duration?

1. For Construction, I supposed it is details dependent (no problem).

2. For Engineering, It is man-hours dependent (but be careful with the coffe break, hot water burns man-hours).

3. For Procurement - This is the big problem of the engineering (P.O. first, before data sheets or any details).

cheers!



Mina Arsal
User offline. Last seen 3 years 32 weeks ago. Offline
Joined: 15 Sep 2008
Posts: 15
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Anoon,

Let me put it in simple words, advantages of this technique are;
1- I always allow overlap between activities without facing out-of-sequence problems (I believe FS relationship is very theoretical).
2- I can lead the site team with early start for the activities instead of starting just in time.
3- I can over come the problem of inaccurate or non available data of activities (e.g. Piping erection activity should be followed by Instrumentation erection activity, if I don’t have accurate data for the instrumentation BOQ I can just open a time frame with FF lag relationship and to adjust the duration so that the start of instrumentation will be after the start of piping erection with lag 7 days).

Disadvantages are;
1- Your schedule could looks in a non professional shape, as for activities which needs few days you are showing them in wide time frames.
2- During updating the schedule you must filter for the activities you decided to make them time frames and start evaluating the driving force, is it still the relation FF or the wide time frame for the activity.
3- Misuse of this method could be start scheduling without gathering real data for the activities.

Mina Arsal
Anoon Iimos
User offline. Last seen 1 year 11 weeks ago. Offline
Joined: 22 Sep 2006
Posts: 1416
Mina,

I supposed Mike doesn’t have a problem with his blood pressure, but I’m sure he has an allergy with FF relationship.

I don’t believe you can evaluate "duration" that way, duration is only driven by resources and decisions.

cheers!
Mina Arsal
User offline. Last seen 3 years 32 weeks ago. Offline
Joined: 15 Sep 2008
Posts: 15
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I am using Primavera 6.1

Yes it generates a critical path, the only difference it is a time frame not an accurate duration. so to keep the activity driven by relation I should evaluate the duration of A2 each update.
Mike Testro
User offline. Last seen 54 min 25 sec ago. Offline
Joined: 14 Dec 2005
Posts: 4403
Hi Mina

Does your method generate a critical path?

Best regards

Mike Testro
Anoon Iimos
User offline. Last seen 1 year 11 weeks ago. Offline
Joined: 22 Sep 2006
Posts: 1416
Hi Mina,

What software are you using? I may suggest that you should also check the "driving data date or status date".

cheers!

p.s. and of course "floats" as well