Critical Path Float?

Sorry Forgot how to use this.

Patrick, Rafael, Vladimir, Stephen,

Good to know that you are still here. After a long silence I'm here again. I'm currently organizing a conference called Creative Construction (more info on www.cc2012.org) We are 150 abstracts so far, and we are beyond on almost every deadline, but I would be glad if you could participate with presentation. 

Stephen! We could settle down this Drag issue when precedence diagramming method is the scheduling engine, and we could meet each other face to face. If not in Budapest, then the next occasion could be the IPMA word congress in Create, where I'm also in the scientific comittee.

Now my answers to Richard

1) Generally there is a longest path from the start to the end node which is called critical path. So generally, my answer is yes. But..... and here comes an example.  You have got A, B, C  with 10 days each. And FS0 from A to B, and from B to C. Now the longest path is 30 days, and this is the critical path  and with zero total float on each activities. (This was the general yes)

Now assign a start later then day 15 to activity B. Well B, and C remains critical, but what about A? It has 5 days float. To continuethis  assign the contracted date to activity C e.g. finish on day 40. At this case situation is more interesting because each and every activity have a float, and so one. This kind of situation can arise in case of constraints (this example), in case of resource limits, different calendars etc.

2) generally yes but...

3). generally yes   but ....

Was good to find you in the same topic :)

Hi Andrew,

Question 1: No, the critical path may start at a point within the schedule (eg, a site access date) and may finish before the final end of the schedule (eg, the hand over of a plant to operations whilst there are still low priority elements of landscaping to complete).  The nature of the ‘path’ is defined by the contract.  For options on the best definition see: http://www.mosaicprojects.com.au/WhitePapers/WP1043_Critical_Path.pdf

Question 2 – Definitely not!  Positive Float may occur on a critical path if the work can be finished earlier than the contracted date. If the contract completion date has a constraint, the critical path will have positive float.  I have seen contracts that require 30 days positive float on the most critical path.

Question 3 – Definitely not.  Constraints should only ever be used to represent EXTERNAL requirements or limitations.  Typical uses are site or work area access dates and contracted handover dates. They may also be used to represent the expected date for the supply of items from another project or the client.

Question 4 – If this is a fact, there should be a Milestone defining the contracted date for the supply of the steel (or several dates if the steel is supplied in batches).    If the steel is supplied by an external third party this is legitimate and represents the contract in the schedule.  If the supply is the responsibility of your organization then you are just being lazy and infective with the planning and need to have the work to supply the steel included either in your schedule or in a dynamically linked schedule. Designing an effective schedule structure is critically important in major projects. See: http://www.mosaicprojects.com.au/PDF/Schedule_Levels.pdf and http://www.mosaicprojects.com.au/PDF/Good_Scheduling_Practice.pdf

If resources are constrained then:



1) The longest sequence of activities may consist of activities that are not logically linked with each other (Resource Critical Path or Critical Chain).

2) Activities that belong to classical Critical Path (calculated without considering Resource, Financial and Supply constraints) may have floats (resource constrained floats) due to resource (financial, supply) limitations.



3) Resource limitations can not be represented as some activities.



4) The steel may be purchased for not one but for many activities and many times during project execution. In this case simple approach with creating link from delivery activity to consumption activity does not work. It may be impossible to know which delivery provides materials that will be used on each activity. At least before project scheduling.



When resource are limited then classical approaches to calculating activity floats based on network logic do not work.



Regards,

Vladimir

Wow, Andrew! Wish I could write so concisely, precisely and correctly!

Andrew



1) Yes

2) Yess

3) Yesss

4) Yessssssssss!!!!!



Thank heavens for a straightforward planner

Can we be simplistic and answer the following yes or no?

1. The critical path must be the longest path from start to completion.



2. The only way activities on this path have float is because certain activies are constrained?



3. Constraints are really activities not defined on the network, (Because they may be by others outside the contractors control.) activities up to starting a steel frame are non critical because steel start is constrained by a steel delivery milestone (steel has been procured by client to a set delivery date.). All following activities are critical. The delivery milestone has behind it a series of critical activities not defined in the programme.



4. If an activity "steelwork procurement by others" had been included in the nework (from contract award to steel delivery (F-S) Then that activity would be on the critical path, and all activities on the longest path would be critical.



Hope that makes sense, from a simple building planner.

Hi Richard,



Please follow this thread (http://www.planningplanet.com/forum/forum_post.asp?fid=1&Cat=5&Top=30236). There are good points on this discussion that covered your query.