You’re welcome Shahul.

The following link will provide you with an example for an application of a constraint type that break the rules of CPM but in this rare occasion is useful and has no effect on other activities. At times even the use of these is the only or best way to model your plan.

http://www.htcprojectcontrols.com/TTB2004-2.pdf

Here you will find the rare application of finish to start relationship along with the also rare application of negative lag.

One approach at times I practice, because constraints are not so frequently used, is to model what I want to do in a very simple schedule and move the model by simulating updates to see the effect on the practice schedule.

Best regards,
Rafael

Shahul

This is determined by your contract documents.

Many times only Contractual Milestones are allowed to have artificial constraints, at times it is a mandatory requirement as to show negative float. Other contracts will allow you to use whatever is reasonable to plan your job but to be released if interfere with delay analysis, this is how I believe it should be.

If your contract allows you to decide which constraint to use and which not to use, in my opinion, only those that could be handled by the original CPM model with the addition of hidden internal logic should be used, otherwise no.

Date constraints such as SNLT, FNET, mandatory-start-on and mandatory-finish-on will override the basic premises of CPM and should not be used. The same rule shall be applied to artificial constraint to algorithms. Any other constraint that create negative float shall also be avoided; sorry this is the most commonly allowed and sometimes is a mandatory requirement as it calls to the attention some milestone date (or contract finish date) is forecasted not to be met.

In the case your contract mandate the use of some constraints or if you feel the need to use some that cannot be handled by the standard CPM algorithm you should know and investigate how some schedulers though the use of global changes toggle off and on some of this constraints. I find the trick cumbersome and prone to error. SureTrak, the software I use, is not able to make any global changes on constraints; its global changes function is very limited.

The book CPM in Construction Management, By James J. O’Brien, Fredric L. Plotnick is an excellent source from which I extracted some of the above information. The following link will give you limited access to a preview on the topic of Artificial Constraints. If you don’t get access try again usually at second click works.

CPM in Construction Management, By James J. O’Brien, Fredric L. Plotnick

Best regards,
Rafael