Automatically Calculating Durations in P3

Roger:



One example of using a SF relationship:



Let us think of a one story rectangular industrial building. Different discipline or trade work is hanging from the roof structure, like main electrical distribution, lighting, HVAC, compressed air, etc. The advance of work is lengthwise, for example from East to West. Some trade work need to be installed before others, for example A before B. Let us also assume that A and B do not span the whole length of the building, but they overlap at the middle of the building. Let us assume also that your schedule is not a detailed schedule so you have one activity per trade for the whole roof. B goes from the East to the middle and A goes from the middle to the west of the building. You can start A and B any time independent from each other, but you cannot finish B until you start A and do some work in the middle of the building. Therefore, you need a SF relationship from A to B with a lag.



You need to use many SS and FF relationships, and some SF relationships, when you develop a high level schedule like when you need one for bidding a job.



One more example of a SF relationship:



In a commercial building let us say that activity A is a main electrical feeder that comes hung from the roof inside the ceiling and feeds a distribution panel or load center supported on a light weight steel stud partition. You also have activity B for the erection of partitions for that building section. You can start both activities any time independent from each other, but you need some work (and not all) done on the partitions to finish your feeder. Therefore you need a SF relationship from B to A with a lag.



Tomas Rivera

Altek System

Detailed scheduling of high

performance construction projects

Tomas,



Can you give me some examples of where you would use a SF (start-to-finish) relationship in a network.



Roger

Andrew:



It would be great to have the option of "scheduling durations as interruptible" to apply it to only selected activities.



Also, you are right that this option applied to the whole project is useless for most real scenarios. Even so, it has been very useful to me in some real scenarios (not most though). I have used it several times in real scenarios getting reductions in the project duration. Let me explain.



Some times you have activities linked with SF or FF relationships. Therefore, you might end up with activities which have predecessors to their finish nodes and successors to their start node in the same activity. If it happens that one of these activities is in the critical path, your project finish date would be earlier if the duration of this activity is increased. Or the other option, is to allow the activity to split by means of the function "scheduling durations as interruptible".



Also, not only you can benefit from earlier project finish dates; but also from increased project float when having this type of activities not in the critical path.



Tomas Rivera

Altek System

Detailed scheduling for high performance

construction projects

Premashish:



I am sorry I cannot give an option in P3e/c to the function "scheduling options as interruptible" in P3, because I do not use it yet.



Tomas Rivera

Altek System

Detailed scheduling of high performance

construction projects

Alternatively, define a global change to impose early start constraints. However, what you then have is a picture, not a plan !.

The dates exported from P3 are calculated so when changed and imported they will recalculate when scheduled. If you were to say change some durations the dates will recalculate differently.



You will need to export/import the four constraint columns if you wish to use Excel to set constraints. I suggest you set some constraints on some activities before exporting so you will see the codes that P3 uses for each type of constraint.



Paul E Harris

Eastwood Harris Pty Ltd, Melbourne, Australia

Planning and Scheduling Book Publishers, Training & Consulting

www.eh.com.au

Hi there, I tried the way that mktse says. By importing my new EF and ES from Excel to P3 it doesn’t produce any constraint on related activities; therefore when I schedule it by F9, again dates will change again. Is there any sort of import rule that I can tell P3 import my dates as constraint or expected finish?

Hi there!

The option "schedule durations as interruptible" must be implemented for each task independently. Unfortunatelly P3 has ability to apply this rule for whole project. That’s useless for most real scenarios.

Tomas,

I’m a new member. I was going through new/old posts and came across your offered solution to Madahav’s query. Unfortunately the option of "schedule durations as interruptible" is not available in P3 e/c. I just wonder why such a fantastic option was missed out in P3 e/c.It may not sound to be a good option to some, but it surely allows to stretch an activity more than it’s original duration, as driven by it’s predecessor’s FF relaionship. I’ve trying hard to find an alternate to "interruptible" within P3 e/c. Would appreciate if somebody could suggest a solution.

A late coming suggestion "How about to do it on Excel".

For Act1, we have ES, EF and DUR

For Act2, both ES and EF is equal to the Act1 ES/EF cells



So if change the cells valve of Act1, the others will be changed auto by the formula.



Then import the dates into P3 for chart printing, of course, if you want the duration is auto calculate under different calendar, the import rule is ES on Excel will be import as start on constraint, EF will be import to expected finish on constraint, then F9. Finally, use global change remove all constraints.

Madhav:



There is another way you can try, although it will not give you everything you want.



If you set up your activities as you said and give activity 2 a duration say of 1 day, then when you schedule your project you can select in options "schedule durations as interruptible". This way your start and finish dates of both activities will be the same, but your duration for activity 2 will stay in 1 day. Also when you display or print a bar chart activity 2 will show one continuous bar from the start date to the finish date. This will treat the rest of your project the same way, and might change other activities dates and your project finish date.



Tomas Rivera

Altek System

Detailed scheduling and control of

high performance construction projects

Dear Madhav,



I quote your example here for easy reference:



Quote:

Act 1 - start - 1/1/04, Finish - 20/1/04

Act 2 - I don’t want to insert the duration for this activity; instead, I want P3 to calculate the same based on a SS and FF relationship with Act 1(assuming no lag). So whenever I change the start, finish dates or duration of Act 1, Act 2 should be adjusted accordingly. Is this possible to do in P3?"UnQuote



By default P3 will show duration as 1 for Act 2, even if you setup SS and FF relationship with Act 1 and whatever you schedule by pressing F9 or so, the Act 2 will be finishing with Act 1 based on Act 1’s latest finish date. In order to have realistic dates for Act 2, we must enter the duration for Act 2 first, then schedule it by pressing F9, then you can change the Act 1’s duration or dates to see the effect on Act 2, (Note: F9 shall be pressed again).



If your example dates are Actual Start and Actual Finish in Act 1, well, then you can use Act 2 type as Hammock, then According to your relationship, Act 2 will show summary of Act 1’s Start & Finish Dates. But this hammock will be useful if you have more activities in a network and want to see a summary band of start and finish. Anyhow i don’t think this is the one you expect from us.



Regards



Daya

I mean if the link remain duration and schedule percentage is flagged on.



Also if I do not like this option.

Steven



You may want to explore the Autocost rule “Perform these calculations during each scheduling computation”.



My understanding is that with this option unchecked then Hammock cost and resource information is not updated at each schedule computation and this information may be manually updated. Be sure not to use the “Update progress” function as this ignores all Autocost rules and the schedule is statused as if it had progressed according to plan.



I suggest you read the help file and create a small test project to see how this function works.



Paul E Harris

Eastwood Harris Pty Ltd, Melbourne, Australia

Planning and Scheduling Book Publishers, Training & Consulting

www.eh.com.au

Steven,

You can not update an hammock independently from its under-laying activities. Here the last statement of my post “You may have a problem with this solution if the Act2 progress is independent from Act1.”

Can you progress a hammock independantly of its underlying tasks ?

Steven,

This may be a solution, but at every update must run the global change. If you want the consistency of the dates between the activities.

If the activities to be mirrored are several it may required more global changes.



Another solution, if the dates must be equal at all the time, should be to use an “hammock” activities. P3 will estimate it duration, based on the Successors (linked by a SS relationship) and predecessors (linked by a FF relationship).



You may have a problem with this solution if the Act2 progress is independent from Act1.

Could try setting the expected finish constraint = ef as a Global Change