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A good methodology to apply regarding Constrains?

6 replies [Last post]
Sat, 2009-11-14 20:16
Jose Ramirez
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Joined: 6 Sep 2008
Posts: 105
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What would be a good methodology to apply regarding Constrains on a Schedule?

I was giving the following schedule to correct:

Total Task in the Project: 1660
Normal Tasks: 1018
Milestone Tasks: 462
Summary Tasks: 180

Constraints: 329
Open Ended Tasks: 959
Out of Sequence Logic: 7
Lags Longer Than 0 Units: 75
Negative Lags (“Lead”): 145 (see example below to see how the issue was corrected)
Positive Lags on Finish to Start Links: 19 (see example below to see how the issue was corrected)
Start To Finish Links: 120
Lags between tasks with different calendars: 6


What I have done so far for the LAG Problems:

Example:

Task_ID 545: “TRA Sep/09: Steel 1 (structure PH I, EA, PP, FF, CL)”

Link Type: FS [ 545 --> 785 ]

Task_ID 785: CIV CV Structural Steel

Lag Link Type: [FS] Lag Link Duration [70]

So these is how I corrected these issues:

Example:

Task_ID 545 [FS]--> Task_ID 785
Task_ID 545 [FS] --> Task_ID FS_545:785 (Duration 70D) (*lag to task conversion) --> Task_ID 785

Or:

Example if the task had a SS Lag with Duration of [70]:

Task_ID 545 [SS]--> Task_ID 785
Task_ID 545 [SS] --> Task_ID SS_545:785 (Duration 70D) (*lag to task conversion) --> Task_ID 785

Now to my Question:

How should I deal with the issue of the 329 Constrains (I have read many of the previous post on the creation of a Sub-Project by Mike T and others “For the Dates of Deliveries of Construction Equip/Supplies/Systems/etc”. I also have been made quite aware of how the constrains can distort the critical path and how it’s so difficult to do any critical path analysis or any sort of risk management on a project with so many constraints.):

I have included the list of Activities with the Constraint Type: (P.S. I Did Not Create This Schedule)

[ID] [Task_Type] [Activity Name] [Constraints]

[101] [SM] [ENG MEC Water treatment system; order documents avaiCLle] [(Type)As late as possible]

[119] [SM] [ENG MEC Surveillance system; order documents available] [(Type)Must start on]

[479] [Task] [FAT Alternators 1-2] [(Type)Finish on or after]

[572] [Task] [TRA Nov/09 Engine lube servicel modules 6-1] [(Type)Start on or after]

[576] [Task] [TRA Dec/09 Power house ventilation system] [(Type)Start on or after]



Well Once Again, Thank Yyou to anyone who is willing to help a fellow planner....

P.s. Mike, Dieter, Rafael If any of guys can share your inputs and your valuable experience on this topic. I know you have dealt with these issues many time over your careers and I would be grateful if you guys could open my mind to a new solution and a new way of looking at schedule constraints. Instead of my currect view and method to just removed them and let the schedule be free to slip [lol].



:P

JoseR

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Replies

Sun, 2009-11-15 13:41
#1
Jose Ramirez
User offline. Last seen 12 years 25 weeks ago. Offline
Joined: 6 Sep 2008
Posts: 105
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Hello Mike,

Would you be so kind to explain to me what you meant by “fill the gap with activity bars that bars that fix a start date.”

This is my understanding of what you said “Go to the bar setting and create a bar for Constraints Dates. Next create a UDF with the dates of the constraints. Have the bar show the Constraints Date information on the right side of it and color it as bright as the Sun.”

I really hope this what you were trying to tell me otherwise am a big Dodo Bird.


JoseR
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Sun, 2009-11-15 14:22
#2
Mike Testro
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Joined: 14 Dec 2005
Posts: 4420
Groups: Building Information Modelling, Content Moderators, GPCCAR Editors
Hi Jose

It is very simple.

For every start constraint there must be a reason why it is there.

Maybe procurement or some sort of outside influence such as Local Planning.

If you do not know why the restraint is set when it is then put in a task bar from the most likely start point - even day 1 will do - and make the duration end at the constraint day - then set FS links to the restrained task.

Name the task something like "Unkown Late Start" and if you like colour it bright scarlet.

Better still work out for yourself why the consraint has been set in place and redraw the programme.

I hope that helps.

Best regards

Mike Testro
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Sun, 2009-11-15 15:05
#3
Jose Ramirez
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Joined: 6 Sep 2008
Posts: 105
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Thank you Mike, for making this clear, I totally understand now.
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Sun, 2009-11-15 09:22
#4
Rafael Davila
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Posts: 5241
Groups: Spider Project Team
Jose,

I would be tempted to follow last advice by Mike Testro: "strip them all out and start again".

By the statistics on your schedule report this is not a CPM schedule and logic, if any logic, it must be wrong.

Although I never say never, I have never used negative lag, over a hundred activities just makes no sense as well as the amount of open ended activities, this is more like the Bar Charting with a few relationships some MS Project schedulers do. One of the not uncommon relationships I have seen done by MS Project schedulers is to tie two activities with a FS relationship with negative lag as to mimic laddering or overlap of activities, this because MS Project only allows for a single tie between two activities. This approach prevent open ended activities, other MS Project schedules frequently follow the other option, to tie activities by a SS and positive lag relationship and leaving open the end of the intermediate activities.

Some MS Project schedulers believe that they are creating true CPM logic by moving activities and forcing the software to hold it by automatically inserting constraints on start and or finish date. If the schedule was created at a design office there is a possibility it was created in MS Project and then transferred to P6.

Kind of profiling, yes it is.

Best regards,
Rafael
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Sun, 2009-11-15 06:00
#5
Mike Testro
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Joined: 14 Dec 2005
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Groups: Building Information Modelling, Content Moderators, GPCCAR Editors
Hi Jose.

The only way to deal with this is - as you have already stated - to remove all constraints and lead lags and fill the gaps with activity bars that fix a start date.

I do use ALAP for design and procurement tasks linked to the 1st activity that requires the input.

Also if you are creating a "window" for other trades to occupy between a ASAP task and an ALAP task.

Otherwise strip them all out and start again.

Best regards

Mike Testro.
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Sun, 2009-11-15 12:57
#6
Jose Ramirez
User offline. Last seen 12 years 25 weeks ago. Offline
Joined: 6 Sep 2008
Posts: 105
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Hello Rafael and Mike,

Thank you, for your advise.

Rafael, yes the schedule was created with MS Project by the folks at MAN Diesel (Some German Co.?) and I was the silly one to imported it into P6.

I new that this schedule was not good, no wonder i got 53 pages of issues when I executed the Schedule Val. Report via Pertmaster.

I was trying to tell my boss that we require more then two days to fix all of these issues because he wanted to have this schedule corrected and resource/cost by Monday (Tomorrow). Oh, boy.

The Other Issues are that the task names are really weirdly name: (i.e. by parts names or statements no where close to how I normal name a task (i.e. Firehouse: Install Rebar). So, reading the schedule to know what we are doing is a bit tricky because I really don’t know what they mean by Install Fire House?. I guess someone is delivering a Fire House that day to be installed. Lol.

Well, Thanks again Mike and Rafael for all your time and help.

JoseR
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