(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.
Hi Planners,
I just moved to a an existing project (consultant) and the program has already been approved. Actually, 35% of the time has already elapsed. My concerns are the following:
1) The activities in the project were hard linked causing the schedule to have a huge negative floats due to the delay of an approval. For instance, the plastering for second floor cannot start unless the plastering for first floor is finished, same with most of the MEP items. The sequence of works is already established on the structural so, imo, there's no need to link each activity per floor to floor.
I discussed this matter to the PM and he said this is how it was approved and if we want to change it it will be an acceleration (which means with cost implication). We discussed it could be the resource allocation btu when I checked it, the resources were not leveled. I suspect it's deliberately done that way or the planner just had that methodology.
Now it's giving is a huge negative float and can be used by the contractor for the time extension.
What should I tell the contractor or to my boss? Should I just let it that way?
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The following might help you understand resource leveling using P6.
http://ronwinterconsulting.com/Implementing_Resource_Leveling.pdf
As you can see these links are called soft-links and there are two methods, one is using the computer to take care of it the other is manual. The important thing when using manual is to recognize links do change as the schedule progress and these must be corrected manually to reflect changed conditions. Your job have changed conditions and the links must be revised, you can use the reference as to substantiate your argument.
Note I added a video link to my previous post in case you want to take a look at it, this you should be able to model within P6. Probably you will have to work with the prioritization issue as it might be implemented differently in P6, but if you have different prioritization levels and you can define a UDF then maybe this is the way to go.
Hi Rafael,
This is what the ideal programming that I was talking about. In P6 however, you have to set Max Units for the Resources to work on this calculation, otherwise it will give another result. If it's hard linked, then this option will be superceded, however, you set your resources availability at some point, by the links, thus, activities that can be done in parallel will not be indentified by the program, unless you manually edit the sequence and check the resource allocation curves. Your example is my ideal scenario.
Thanks Rafael for the wonderful example.
Best Regards,
D'Artagnan
D'Artagnan,
Do not overlook the effect out-of-sequence algorithm might have on the schedule as it makes some assumptions to solve the issue that might not reflect true schedule. Perhaps this is why an activity is being delayed and you cannot see the invisible link the out of sequence option of retained logic can be creating. Try changing the option to progress override and tell us if you see a huge difference. Keep in mind progress override is not a solution but a chosen option to solve logic that many times only can be solved by hand.
Justin,
That activities have no logic links does not means there are priorities, your software shall be able to solve resource constraining using activity priorities and only break the prioritization if it delays project completion. It is just a matter of learning how to handle activity prioritization under resource leveling.
In the following example I have 3 crews for villa construction, a very simplified resource allocation as to show the strategy. If you change priority of Villa 4 say to a value of 30 it will be the first scheduled villa along with villa 1 and 2.
If you do not use prioritization most schedules can end up un chaotic distribution, we leave the optimization algorithm for last resort as this does not takes into account activity prioritization in order to get the shortest possible duration, a constraint that would prevent it to do so.
Best regards,
Rafael
Hi Justin,
I had already come to that point of view, as i mentioned, it could be the resources allocation but to the extent of my analysis. My opinion, if resources are issues, this can be analyzed by 'resource levelling' and not by hard linking. The floats would be used properly. I am seeing a sequence of activities, let's say on the second floor with 0 day gap and, on the 17th floor, same sequence of activities, with 6 months gap. That's not logical. On the second floor, my contractor can start water pipes installation on the ceiling after blockworks but on the 17th floor, they say they have to wait 6 months to start the same. And it's not resources issue, i checked.
Thanks for reply. I would like to hear more inputs.
Best Regards,
D'Artagnan
Hi D Artagnan,
I have a doubt from a contractor planner point of view , say for an example Project consist 600 individual villas duration of 24 months , to construct 1 villa needs 6 months minimum (CPM will show the same) , then contractor should decide in which way he should link each villas , so that he can spread those 600 villas over the period of 24 months , Logically there is no link between each villas , but contractor must show some link to his schedule , so that he can put up a plan before client
Simlarly, logically there is no relation between plastering activity of 2 floors, but it depends upon contractor's crew he will decide,
If contractor planner followed only the logical links between his activities, project would have finished before 6 months of contractual completion period
Then how contracting company’s owner will allow his planner to present a schedule showing before 6 months completion schedule.
Regards
Justin
Hi Mike,
At first, I suspected the resource deployment but when I checked the resource allocation, it was not the case. Plastering, Painting, MEP Activities (First to Last Fixes) - all were linked floor by floor. For instance, second floor - first fix of MEP starts immediately after blockworks but checking 19th floor, the gap is because the hard links.
We're only up to blockworks (actual works) as there was a delay in the issuance of ID package. The structural works are on schedule but the schedule update is showing "really huge" negative float. The first time i sat with the schedule, i already suspected an artifical negative float. I am just having a hard time convincing my manager and i am not sure how to deal with it since it's already been approved by some senior planner.
Thanks for the insights.
Hi Rafael,
Thanks for explanation. Very very helpful to support my argument.
Best Regards,
D'Artagnan
The sequence of works is already established on the structural so, imo, there's no need to link each activity per floor to floor.
I agree with you 100%, theoretically if you finish all structural works and only then you start with the interior finishes you shall be able to work on all floors at the same time if resources and material handling have no quantity constraints. If plastering is your first finishing activity it can start at the same time in all floors. The redundant links are forcing a logic that is not necessarily true. There is no excuse to stop plastering on the second level as there is nothing that prevents him to do so, if the schedule says otherwise then his submitted schedule was in error.
No matter what, the contractor is responsible for finishing the job on time unless he proves otherwise, if he used wrong links, links that are not necessary then this is no excuse to shift his responsibility to others. Of course in such case there is the possibility of some disruption but not necessarily a delay nor what seems like a work stoppage, he is going too far. I work for general contractors but we never abuse in such way our schedules.
Question his schedule to be in error, with unnecessary redundant links that prevent possible resource re-distribution that do not necessarily mean a delay. Here this tactic would be interpreted as an artificial float reduction technique, a technique considered dirty. I would tell him that he will bear responsibility for any delay due to undisclosed errors in his submitted schedule.
At home the acceptance of a submittal do not relieves the contractor from complying with the specifications, if he is in error and no one find it it will still be his responsibility. If the contractor wants to validate a deviation he must specifically warn of the deviation, otherwise it might be missed by the reviewer and this would be unfair trick. In the same way if the CPM had some soft-links that are no longer valid and this possibility was missed he is still responsible to make the necessary links corrections.
In order to reduce such schedule claims [abuses] it is common practice for our CPM specifications to prohibit soft logic links in lieu of software driven resource leveling. Our specs frequently say that If the contractor uses such links it will be at his own risk, and the owner reserves the right to ask for such dependencies taken out for any claim analysis. To me it is so logic that if there are no such links even the explicit prohibition is unnecessary, perhaps designed for fools that would present such argument.
Maybe you got a good example where not solving out-of-sequence logic, works against the Owner [usually works against the contractor - LOL], even when using the retained logic option.
Hi D
The only reason to link like tasks between floors is to control the level of deployed resources.
Do a check on the planned level of - say - plasterers and compare it with th actuasl deployment.
This will give you the answer as to whether the links are justified.
Best regards
Mike Testro
Email: PPadmin@planningplanet.com
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