over use of SS relationships?

Hi Cam

Short answer - there is no place for SS or FF links in a construction programme - only FS should be used.

Best regards

Mike Testro

Hi,

         Try to use only FS relations. Because open end activities cause lot of troubles in your overall scheduling...... FS relation makes schedule simple & good.

thank you.

What if I use SS and FF relationship simultaneously ? Will that has any efferct on overall schedule?

Cheers

Saurabh

Hi Saurabh Kumar,

                                 What do u meant by using simultaneous???? Look we can use the schedule relationships in any way, if it is logic. The main problem in using relations other than FS is the activity becomes open. But you can close it by using another relation...... see the problem lies in how we use it......if it is really logical for you....then you can use any relation....but for large activity schedules....if you want be the schedule perfect you have to give importance to FS relation...... PM book also instructing us to do so..............

Hi all

I am a civil engineer and i have 4 years of experience as a planning engineer in my total 9 years of exp. Recently, I am looking for a job in india- chennai,bangalore.

As you pointed out that use of SS & FF relationships will create pbms when scheduling. I dont understand this concept as I used SS & FF relationship mostly in our program in dubai as our most of the activities takes place simultaneously. Also, I was adviced by my manager not to use FS with negative lag as it is illogical.

So could any one of you pls explain whether we can use FS with negative lag and what is the actual issue in using SS& FF / FS- lag relationships?

Please help me in this regards.

Thanks

M.Velu

9600996598

Hi Velu

As soon as you put a lead lag on a SS link you have changed its nature to a FS link because you have guessed that at some time along the predecessor bar sufficient work will be finished for the successor bar to start.

Your guess will almost certainly be wrong so you must break down the long bars into shorter tasks and link each one FS.

Other problems with SS links are:

1 Open ended tasks = massive float

2 Progress past the SS Lag and all successor logic is gone.

We once had a discussion on PP about FF links and not one planner could tell me where such a link would be used in construction programming - except to retain logic on otherwise open ended bars.

Use of SS FF links should be banned.

Best regards

Mike Testro

Hi Mike,

                  You are right.... I support you............

It is a misconception that schedules with only FS links are always better than those that include the other type links.

For example take a look at the following schedule, before resource leveling it seems the group without SS links is equivalent to the other group.

But after resource leveling you will find it is not, and perhaps the schedule with SS links yields better results as it keeps the Cement Plaster operation continuous instead of split with a time lag. Good software shall give you the option to allow resource leveling to split the activity if not doing so the project completion is delayed.

In addition very frequently it is easier and more intuitive to use those links to create the overlap. Assume that in your Country jobs are done without resources, or Courts do not require you to show your schedule considering resource availability and schedule the following without any regard to the possible effect of resource leveling.

Why do you believe the PMI nor any software developer has ever banned SS/SF/FF links?

It is a misconception that the use of SS links creates open ends, what creates open ends is the lack of a successor activity.

Hi Rafael

Its good to hear from you again - we have had this debate on PP a number of times and you are still propounding the same errors.

The reason why software developers allow SS FF links is that none of them are Builders.

Such links do have a place in other industries such as IT or Pharmaceuticals - in fact they are essential if you are setting a ladder programme for manufacturing.

But they are NOT fit for construction where a detailed bottom up FS programme is the only way to replicate what is going to happen on the site.

And appart from that it is impossible to impact delays accurately as and when they happen with global tasks at level 3.

Furthermore I would never allow the software to level resources - if it has to be done then I would do it by hand.

Best regards

Mike Testro

Hi Rafael

Now you are going into the ludicrous detail of micro programming.

A concrete pour on a slab is a single gang deployment combining different skills to complete the task.

Best regards

Mike Testro

Mike,

In the construction industry there are thousands of occasions where overlapping of activities is appropriate, where there is need for a continuous activity model.

As a matter of fact time lag, different from volume lag, the traditional, is common. Take for example a single day, detailed scheduling of slab concrete pouring.

Concrete pouring would be scheduled to be a continuous operation, say 4 hours while at the same time troweling would be scheduled to be a continuously overlapping activity that will start a couple of hours after concrete pouring starts and finished a couple hours + one after concrete finishes.

If you pour the whole volume of work in one hour troweling will start after concrete pour starts  the same amount of time as if poured during four hours.

Cement plaster and many other activities such as pipe laying do behave in similar manner and are best modeled using continuous activities.

Good software shall provide time lag as well as volume lag to be used depending on the modeling needs.

I did not know Asta is software not good for Construction as it still provides SS/FF/FS link types. Probably they should have a Construction oriented version. Of course this argument is directed to you as I agree with Asta choice, in my opinion good software.

Best regards,

Rafael

Mike,

Concrete pouring is not always a single gang operation but many times a several gang/teams operation. The concrete finishers might belong to a different gang that can perform work on other activities the same day while the concrete pouring crews will not move to different activities on the same day. Good software shall allow you to model such resource allocation on a single activity with no problem at all.

I agree this sample job is micro-planning, too much for me, same as splitting the activities into many separate chunks.

In any case modeling of Cement Plaster as in the first sample is in no way micro-planning, micro planning is slpitting the activity in many. Instead of 3 activities you would need 9, and if using different calendars with differnf workdays the duration distribution can become tricky.

Best regards,

Rafael

P.S. I was missing this never ending excercise