Website Upgrade Incoming - we're working on a new look (and speed!) standby while we deliver the project

Tips on using this forum..

(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?

(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.

Floating Values

13 replies [Last post]
Wed, 2006-01-18 02:46
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
I cannot change the late finish dates and dependently the total float values. After rescheduling, all changes returns to the ald values. What can cause it?

In addition I want to know that if there is a way to specify float values to a constant. For example 5 days of floating will be a floating value for all activities.

Any help will be appreciated much!

Top

Replies

Thu, 2006-05-11 21:55
#1
Zhang Haixiang
User offline. Last seen 4 years 20 weeks ago. Offline
Joined: 14 Apr 2005
Posts: 250
Groups: None
I think you need to learn Critical path method first.
find some articles about CPM.
Then make a small project with several activity e.g. 10 activities, then calculate ES EF LS LF FF TF then you will understand every thing.

LF - if you finish the activity later than LF, the whole project will be delayed

For example, a single activty project say activity A dur 10 Day ES 1May. the project contractual finish date is 20May
so for A ES is 1May , EF 10May
if A finish on 20May, it still meet the contract date of 20May
so LF for A is 20May, the TF is LF-EF =10 days.

you can add TF to all activitis by shift the project compeltion date. But for each activity the only way is to add constain
Top
Thu, 2006-01-26 04:06
#2
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
Francis,

Thank you for your reply.

I spent considerably long time and much afford on this floating values subject although I am not an experienced and long timed primavera user.

Your comments has been so helpful to understand the phenomena. I am more relaxed about it now.

Sincerely,

NS
Top
Tue, 2006-01-24 08:16
#3
Francis Moyalan, ...
User offline. Last seen 5 years 41 weeks ago. Offline
Joined: 12 Feb 2005
Posts: 105
Groups: None
Nurhan,

See what the consultant is saying is logical to a certain extend,

I am working in a residential project and it contains podiums divided into 18 areas,

So each area is independent of one another and the precast erection in these areas happen independently,

So sometimes due to logistics problems, some areas will be lagging behind the target dates,

In this case, if the roof slabs of the adjoining areas are not connected logically the slabs will be showing all unrealisic floats, i.e if sometimes the roof slab in a particular area is not completed and if we want to know how much is the float available for completing that particular slab,then the relationship between the activities play a vital role,

I meant to say, total float really depends on the relationship between the activities and on taking the schedule report you will be able to get the open end listed activities and it is ideal to clsoe all the open ends in the program which has to be submitted to the consultant,

Regards,

FMV

Top
Wed, 2006-01-18 10:03
#4
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
Thank you all for your very precious replies.

Steven Oliver, Francis Moyalan, Gordon Blair,

I have not wanted to use constraints, because when you use constraints P3 calculates negative total float and it is not a situation desired for me. I experienced that negative calculation and it is written in reference manual in this way (Page 41) as well.

Francis,

Can you explain how late dates all depends upon the successor activities relationship? I want to learn the logic of calculation for lates. Maybe I can arrange the lates following the successor relationships.

Gordon,

I haven’t thought that large amounts of float was a normal situation and I havent liked it at all. Now, I am learning that it is such in the planning world of primavera and I am not going to concern about it.



Primavera sometimes calculates zero float and sometimes negative and sometimes 400 days of float. (They are individual activities) I wonder what to say If my client says I do not want such floats.






Top
Wed, 2006-01-18 08:43
#5
Gordon Blair
User offline. Last seen 7 years 4 weeks ago. Offline
Joined: 29 Jul 2005
Posts: 166
Groups: None
Nuhran Serin,

As I understand it, what you want to do is specify latest dates for completion of individual activities. This may be achieved by setting ’late finish’ constraints in the activities. For example, if you had a design brief that had to be out for review (for internal political reasons) on the 1st Feb, when the review period wouldn’t start until mid march, you would apply a late finish constraint to that activity of 1st Feb:

Activities box

Constaints Tab

tick Late Finish button,

pick date from the calendar.

This will hold in (constrain) the late date to the date you want, even after scheduling.

I would suggest though, that there are very few reasons for doing this.

1) ’Political’ reasons which have little to do with the running of the Project.

2) A project lacking in comprehensive detail in activities and/or logic. If there is an occurence or activity or date that needs to be met within your project, it should be shown as such within your plan.

Once you have captured all of the factors driving the end dates of your project, you may well have some activities with large amounts of float, this is not something to fear, or to hide, it’s just the way things are.
Top
Wed, 2006-01-18 08:40
#6
Francis Moyalan, ...
User offline. Last seen 5 years 41 weeks ago. Offline
Joined: 12 Feb 2005
Posts: 105
Groups: None
Hi Nurhan,

Steven’s reply is logical for your query,

Since P3 is making backward pass for calculating the late dates, if the must finish - constraint is not given in the project over view, the value will remain constant or uniform, when you are scheduling every day,

but when, you are giving a must finish by constraint then that date is taken for backward pass by P3 and the total float will go on decreasing every day unless the activity is not updated,

And the late dates all depends upon the activity’s successor relatioship,

if the project must finish by constraint is not given, in that case if an activity is getting delayed , then also the total float will remain positive and you can’t make out the exact delayed completion of the project,

Thanks,

FMV
Top
Wed, 2006-01-18 08:15
#7
Michael Crawley
User offline. Last seen 19 years 3 weeks ago. Offline
Joined: 5 Dec 2005
Posts: 13
Groups: None
if you do not want to show the dates that the software is calculating for you. what’s the point in using it. as it is just a picture you are drawing why not just use an excel spreadsheet and type in the dates you want and fill the cells with nice colours.

if you do not believe the dates that the software is giving you then calculate it manually to check it.
Top
Wed, 2006-01-18 08:09
#8
Steven Oliver
User offline. Last seen 12 years 14 weeks ago. Offline
Joined: 8 Nov 2002
Posts: 313
Groups: None
"Late Dates" are generated by the "Backward Pass", that P3 performs during the scheduling process.

The date specified as the "Project Completion Date" specifies which date the backward pass uses in the calculation, or if the "Project Completion Date" is not given then the finish of the last activity can determine the final date.

To constrain the completion your project to a specific date apply a finish constraint to the activity.

It is possible to artificially constrain activities to a certain Total Float, but I personally wouldnt.

Try this out on a single activity, and understand what the dates P3 is giving you are.

It is possible to constrain activities to certain levels of Total Float, personally I wouldnt, but you could.

Top
Wed, 2006-01-18 07:34
#9
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
As I written, lates are given by the programme and they are not my values I want to assign. I want to assign my values. Besides, the late dates what programme gives are rather bad dates. And I cannot see any logic behind it.(I mean for assigning lates).
Top
Wed, 2006-01-18 07:14
#10
Michael Crawley
User offline. Last seen 19 years 3 weeks ago. Offline
Joined: 5 Dec 2005
Posts: 13
Groups: None
why???
Top
Wed, 2006-01-18 06:39
#11
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
In other words, late dates are given by programme.

I want to give late dates myself. My question is how it is possible?
Top
Wed, 2006-01-18 06:12
#12
nurhan serin
User offline. Last seen 17 years 23 weeks ago. Offline
Joined: 6 Jan 2006
Posts: 10
Groups: None
Marcio Eduardo Thank you for your reply. I am not trying to change dates, but late dates or float values. I have no problem changing early dates. I have problem with changing late dates. They remains the same after I scheduled the activity with changes that I made. So, the total float remains the same. Because late dates cannot be changed. It is something like that as if a determined total float value is memorized by primavera and you cannot change that value at all.
Top
Wed, 2006-01-18 05:57
#13
Marcio Sampaio
User offline. Last seen 12 years 26 weeks ago. Offline
Joined: 7 Nov 2005
Posts: 658
Groups: Petro-Chem / Oil & Gas
Nurhan Serin,

Are u trying to change the dates manually?

To modify the dates you must change relationships, lags and/or durations.

About the second question, I think it is not possible to do.

Kind regards,

Marcio Eduardo
Rio de Janeiro - Brazil
Top