Rafael Says Let’s Challenge Mike.

Mike,
I understood that we discussed if SS/FF relationships shall be used in project modelling. Why PowerProject and software query?
Best Regards,
Vladimir

Hi Vladimir

That was quick.

It is just that Rafael asked you to think of a problem that I could not answer - it was the bathing in baby oil that got me going - so I decided to throw it open to the PP forum.

The challenge is not restricted to Powerproject in respect of general planning problems but I would not welcome challenges on the entrails of less useful software - Spider excluded of course - any of which I will forward to you for clarification.

Its a bit of fun - lets see what happens.

Best regards

Mike Testro.

Yes, it may be interesting.
If you will not be able to find a solution using PowerProject let me explain how to do it in Spider.
Best Regards,
Vladimir

Mike

Let’s make it a model for CMU Installation, Cement Plaster and Painting something many must be familiar with.

Activity-Duration-Successors
A1 CMU Partitions -30d-A2SS5, A2FF5
A2 Cement Plaster-30d-A3SS10, A3FF10
A3 Paint Walls-30d-A4
A4 Misc. Surface Repairs-5d     

Show us how you will model the network using only FS0 relationships and at the same time all work on the activities kept continuous during any update, maybe at a variable rate, and of course all relationships maintained.

You got to consider activities no A2 and no A3 have other successors and that subdividing the activities in many small duration activities would never show true relationships as you always can further divide the activities as if you were solving a calculus problem. This would be nuts.

Finally tell us why the use of lags makes invalid the above model. Please be reminded that many of the traps with lags are related to updating, these can be avoided with the proper use of your scheduling options. As for example, do not link remaining duration and percent complete, this creates problems with lag on some old software versions, this is a lazy scheduler option as well as any other option that automates updating, the problem is in the options not in the use of lag. Keep as a reference your outdated CPM books but don’t take for granted all you read on them.

Best regards,
Rafael

Hi Rafael

In your model the CMU partitions have a duration of 30 days and after 5 days you can start plastering - in which case there must be a physical reason for break point - so the partitions are in stages the 1st of which has a duration of 5 days - we don not know how the remaining 25 days are split up.

Lets assume therefore that the other stages are also 5 days so we have 6 5 day stages for partions - each of which is a stand alone activity.

So we have six partition stages to be plastered also in 6 stages then painted.

It is very quick to set up stage 1 in 5 day tasks FS0 links for Partition > Plaster > Paint and copy paste to form stages 2 3 4 5 & 6

Then cros link between stages FS0 betwenn trades in each stage.

You now have 18 tasks and the last one - snagging - is linked to the end of stage 6.

That is a pure bottom up FS cascade and it is absolutely clear what the stages and the breaks are.

Furthermore there is no problem with progress up dating.

Best regards

Mike Testro

Mike

By subdividing CMU Partitions into 6 stages then you are opening the door for six out-of-sequence occurrences between CMU Partitions and Cement Plaster after it happens at the first stage there is no reason why it cannot happens during the next stages, most probably it will. Similarly with Cement Plaster and Paint Walls, is kind of complicating things. I accept naming the stages got to be fun.

From four activities now we got into 19, there’s got to be some justification for it otherwise is nonsense.

I never had problems with my updating except when out-of-sequence occurs, why increase the chance? We use the correct methodology in our updating, I don’t see any valid reason to increase the number of activities by a factor of 19/4=~5 and in addition increase the chance for out-of-sequence occurrences from 2 to 12 this yields a factor of 12/2=6 is kind of insane. In this regard I find the first model superior.

Can you be more specific about the progress updating issues your software has? It cannot be something you got out of an old book or someone told you. I want to make sure my software does not show this kind of behavior using our method of updating and calculation options. I would appreciate if you use my model so I can easily follow you; anyway you say it is wrong, just 4 activities instead of 19, is a bargain.

If I got a SS1 (one day lag) relationship how many stages will I get, what if SS0? If it cannot be 0, then Lim (lag --> 0) ?

Best regards,
Rafael

Hi Rafael

The whole point is that if something delays the partition in stage 4 you know precisely where the work stage is and what logic needs to be revised.

This is essential for managing the work and in delay analysis you can pinpoint the precise location that was delayed.

If it is all wrapped up in one global bar you are just guessing.

I have seen worse when all trades are wrapped up in one bar called Internal Walls.

As for updating the percentages are put on a spreadsheet against each activity - this is done on a PDA during the site walkabout.

With such short periods it is either 0% 50% or 100% and if it is a bit out then the number of entries cancell each other out.

Once again with one long bar you are guessing the overall percentage.

The spreadsheet column is then copy - paste to the software and the update is done in 20 seconds. (I don’t think you can copy - paste in Suretrak or P3)

If one stage is out of sequence and you have not adjusted the logic beforehand thhen powerproject will re link around uncompleted work but only if it is a FS link.

If there is an activity that is 1 day long - Pour Concrete Columns for istance - then that is it.

The rule is:

1 trade in 1 location that can work without interuution by other trades.

The trick is to divide your project into sufficient work fronts to acheive this breakdown.

If a task is longer that 14 days it is too long.

I don’t think you have seen the speeded up version of my Bottom Up Demo.

Ping me an email at planning.services@xlninternet.co.uk and I will send a copy.

Best regards

Mike Testro

Mike,
I did not find in Rafael post anything about long activity durations. More than that we recommend to restrict activity durations not by 14 but by 7 days and we still use SS and FF links.
The distance between construction crews at pipelinbe construction is usually 500 meters and the speed of construction is close to 500m/day. And it is easy to estimate where each crew is knowing the volume of work that have been done measured in physical units.

You did not answer Rafael’s question, you discussed other topic.

Hi Vladimir

Even in a linear system such as a tunnel or a pipeline I would use FS links.

PowerProject can use a task per line mode where the different activities are on the same bar.

This creates an image on the chart similar to Tilos or Graphisoft.

Nearly all prgrammes that I have to deal with have multi task - multi location bars and Rafael was talking about a 30 day bar - much too long.

Best regards

Mike Testro

Mike,
we repeat the same arguments.
With your approach 1000 km pipeline model will have close to 1 mln activities and you did not try any project of that size with PowerProject. I don’t think that it will be easy to work with this model. And multiple activities on the same line do not add much to the way people work with the data. Besides your approach means that you replace continious work with discreet elements that creates unnecessary delays.

If you have objective (physical measure of the work performed then long durations do not create problems. If you know the direction of pipeline construction and know that 5km were done you know the exact point where the crew is at the moment. In this case activities may be longer.

So you will agree with Rafael if he will suggest 14 days example instead of 30 days example?

Best Regards,
Vladimir

Hi Vladimir

You are talking about a massive linear project which would be broken down into manageable sections between pumping stations or whatever.

There would not be 1 min tasks in any one chart - max 1000.

Powerproject could do it but I would prefer to use Tilos time chain software for linear projects where out of sequence working would be a rare occurrence.

Rafael is talking about construction work where out of sequence working is quite common and the logic would have to be adjusted.

You cannot do this with a global bar and SS FF links and arbitrary lead lags.

So no - I do not agree with Rafeal.

Best regards

Mike Testro

To all:

Managing the Overlap: Where inserting an additional task is not appropriate, the nature of the gap needs to be clearly understood: Why is this lag needed?

Links, Lags and Ladders


Mike

Mike using percentage instead of remaining duration to update your job is usually erroneous; the software computation for remaining duration will usually come out wrong, in disagreement with true remaining duration. In order to get it right when using percentage duration, got to know actual duration and remaining duration; when linked, %complete = 100x (Actual Duration)/ (Actual Duration +Remaining Duration)

In addition you should consider the following;

PITFALL #1: Linking of Percent Complete and Remaining Duration

I find your approach as another way to model the same thing as if you divide a 30 days activity into two 15 days activities in tandem. Construction jobs at this side of the pond are required to have a scale with maximum construction activity duration of 20 days, waiver to this are accepted if justified and non construction activities such as a delivery are exempted. Our good practice protocols are based on this scale, lag is one of the issues our protocols pay particular attention. It can be that applying this protocol to linear jobs might spell disaster.

I was hoping for you to tell me why my model is wrong, the following link is from a book which its first edition was written over 40 years ago, still on the market but I wonder if up to date to 15 years ago after SureTrak update or service pack C. I believe most of the issues about lag in the US have their origin here, when this book was written and O’Brien was one of the pioneers. He was one of the proponents of constraining contractual milestones and project duration, allowing for negative lag and the cause of many headaches.

Lag Algorithm


In the link you will see an example of the traps in the use of lags, but I could not even re-create the trap in my model using my version of SureTrak following good updating practice. You are welcome to use it as a reference in your quest to invalidate the use of lags in my model. You are also welcome to show us other situations where the use of lag tricks the CPM computations, now we understand your model, let’s move to the next stage.

The idea is if there are traps (we know there are) in the use of lags, let’s go to the bottom of it. I am sure we can get a set of rules that will avoid most of the traps without banning all lags.

Vladimir,

With traditional SS and FF links you cannot fix the distance between two activities so related that if the second is delayed the first must slow down and is also delayed, resource allocation will follow. Probably your software can do that without resort to cumbersome relationships, I am sort of becoming lazy. The idea of having a definition for a SS and FF to create a fixed steps, equal rungs ladder is a functionality I would like to have. I don’t remember if Micro Planner ladder activities behaved in this way but believe it does.

Best regards,
Rafael

Mike,
we repeat the same arguments.
We already calculated the number of activities that are necessary in 1000km pipeline construction project if to use your approch. Dividing the project into small parts is bad idea. These parts are not independent.
And we also discussed that Tilos does not level resources, materials, finances. Maybe it is OK for your projects but not for mine. I chose linear projects because in this kind of projects using ladders is natural and obvious. You did not answer if you understand that replacing continious activities by discreete you make the simulate less accurate. It is your choice what to use in your projects but you did not suggest any real argument why other approaches are not as good.

Rafael,
I already wrote that Spider Project has so called Volume Lags and you can define that the next activity can start after 500m will be done on the preceding activity. This approach is much more practical and safer than using Time Lags. Besides Spider Project has strict links. Activities linked by strict dependencies are pasted and delaying next activity will delay preceding activity.

I don’t know if similar functionality is in MicroPlanner.

Best Regards,
Vladimir

Vladimir

It seems like Micro Planner have something similar, they call it "progressive feed", and yes this approach must be more practical and safer than using lag times. Use of lags will not be enough, SS and FF won’t prevent successor from slipping away. Progressive feed or Volume Lag is more than just a safe substitute for SS and FF, has a lot to do with resources and also with float even in the absence of resources. I know you know it but it is important everyone else get it, sorry for being redundant once again. I bet in your favor that they do not have the reports you have for linear jobs.

Mike

What about resource leveling, without resources there is no job? We got to admit Spider Project provides full CPM functionality into linear jobs like no other software. Why two software packages if you can do it with one? Especially good when you have a combination in a single job. Other Linear Scheduling software provides a lot of beautiful graphs at a high cost but not much functionality.

At times I have a need to keep several activities in a ladder with SS, FF and zero lag for activities that are incidental with another. As for example I might have an activity for placing of rebar on an elevated slab but at the same time the electrician and plumber got to be working in the same area. I need to separate them from the main activity for reporting and coordination with the trades. These activities must start and finish at the same time.

For updating our jobs we use Primavera Post Office, a mini application that can run stand alone. We filter the activities to be updated, a 3 month look ahead and e-mail the filtered Primavera Post Office file. This avoid sending the whole count and looking through a large number of activities, no need to send those previously finished or not in the horizon. When I receive back the file in my e-mail box I update the activities at a click of the mouse without need to make sure all activities are sorted out exactly as per my spreadsheet. Activity fields and resources can be updated as you can customize the table with ease. Sorry using a spreadsheet to update a CPM seems like archaic, no matter what gadget you are using.

Please help me with a list of lag traps so I can make a list for my use as to avoid them. For my laddering I will continue using SS and FF lag without the full functionality you can get with progressive feed, volume lags or ladder type activities, I have no other option with my software.

Use of lag other than laddering represent a mere 1% of my activity count but I am still concerned about this 1% (Total activity count x 10% activities with lag x 10% not ladders = 1% of total activity count).

Best regards,
Rafael

Hi Rafael

Resourcing.

I only use one resource called Hours - the number of which are extracted from the cost plan and then allocated to the respective activity.

Durations are calculated by adjusting the gang size.

I never use resource levelling software because you have no control over what is happening - you may recall the playing piano technique that I described in an earlier thread.

You wrote: "I might have an activity for placing of rebar on an elevated slab but at the same time the electrician and plumber got to be working in the same area."

Are you saying that you arrange your work so that rebar fixers - electricians and plumbers are all working in the same place at the same time? I don’t think so.

The rebar fixers will complete the bottom section and move on - the conduit fixers will follow and then the rebar fixers will return for the top layer.

This is a normal FS cascade of activities - and they do not all finish at the same time - there will be an overlap.

How do you re-arrange the programme when the electrician has fixed the wrong conduit in the wrong place?

Without the level of detail in a FS0 cascade you are stuffed.

I have listed the reasons for avoiding FF SS lags many times on PP before now and you and I and Vladimir have discussed them all.

Laddering looks good on the chart when all tasks are of a similar duration but the symetry goes when they are of different length.

My understanding is that laddering works ok in a manufacturing environment but not so well in construction.

Your updating software is just a spreadsheet application that works with P3 or Suretrak where you can’t otherwise copy - paste the data.

Where you do have a copy paste facility in your software then excell works very well - if you think excell is old fashioned I still use Lotus 123 - a far better peice of kit.

Best regards

Mike Testro

Mike, you wrote:
Laddering looks good on the chart when all tasks are of a similar duration but the symetry goes when they are of different length.

If there are both SS and FF links then it does not matter if activities have different durations. With different durations one or another link will become driving and the works will be done continiously.

I don’t share your attitude to Resource levelling and am sure that Hours cannot be considered as Resource at all. If it is good for you and your customers then it is OK. Our customers are not satisfied with the schedules that are not resource loaded.

Best Regards,
Vladimir

Hi Vladimir

I use a standard resource called Hours because it is quick and simple to resource model a programme.

At the basic level all trades operate in hours in the modelling software so why complicate matters with different types of resource.

You can filter tasks for the relative trade by the task decription and produce labour histograms for each one.

Best regards

Mike Testro

Construction crews include people and machines, people have different specialities. Activity duration depends on assigned resource productivitries that may be defined by people productivities on some works and machine productivities on others. Changing crews you change activity durations and costs. For some machines like cranes their quantity is always restricted and your schedule shall take it into account. And it is nice to get from the schedule resource plans.
I think that defining activity duration you have in mind some crew that will do the work. Then you count the number of people in this crew and multiply it by activity duration. The result become resource Hours. If I am wrong explain what you do.
In any case not all resources in the crew are driving, some of them are not fully loaded, there are also machines, etc. And it is necessary to know the planned quantity of resources on site at different periods.
Best Regards,
Vladimir

Mike

You got the right sequencing of trades. I was referring to the very common sequence you have when you strip your flying forms, one by one with a tower crane, it might be 2 decks per bay, 8 bays per day. You have 16 decks working in sequence, at 3 activities per deck this would yield 48 activities per day only for your elevated slabs, then for your walls you would get about twice, and so on, for a single days work and only for what is happening on the top floor, it is too much, your approach is not practical. Just imagine the printout for a single day’s work at your typical condo, something the contractor has been doing for many years.

Not all of my laddering are progressive feed but most of them, for progressive feed your best option is to use this functionality if available in your software, if not a progressive feed then your option would be SS and FF relationships.

“Your updating software is just a spreadsheet application that works with P3 or SureTrak where you can’t otherwise copy - paste the data.” - Copy and paste is so error prone that none of the serious scheduling software should have it as the mean for updating the whole thing, a more advanced technique is a better way to do it. Copying and pasting thousands of spreadsheet lines just to update a few cells is not an efficient way of doing things.

“I have listed the reasons for avoiding FF SS lags many times on PP before now and you and I and Vladimir have discussed them all. “ - For the moment I have not seen any valid reason on your part, on the other hand there are a couple very specific exceptions on the references I gave you before.

Your approach to resource leveling I find it to be practical. I use the concept of crews where a crew might be composed of various related trades, at times you do not know exactly your final ratio of masons to helpers and unskilled or labors but you know what size crew it will be. The crew will be working under the same supervisor for many weeks and the personnel are not to be moved from crew to crew on a daily basis. This is how construction works are managed, different to the matrix organization a design firm will use to manage their design teams where a designer might work for different jobs, for different PMs and a design trade supervisor. Here each person would be a single resource, each with a particular set of skills.

Best regards,
Rafael

Rafael,
so you also don’t level resources?
It is interesting who level resources. I have an impression that very few members of PP do it. Can this be explained by poor software capabilities, poor data, or there is some other reason?
Best Regards,
Vladimir

Vladimir

Because of poor software capabilities.

You were correct when you inferred I do not level resources. I resource load the schedule to make sure our soft relationships “solved” the issue. This prevent us from unlevel the schedule, as a consequence we are missing schedule compression options.

Most of our Contractors favor the use of "soft relationships" because our software after resource leveling does not show resource critical path nor resource float, with the lack of this functionality float is meaningless under limited resources. You lose track of what is driving your activities.

Traditional resource leveling reports are kind of cumbersome and even hidden, some P3 and P6 users do not even know about these reports. SureTrak do not provide me with such a report.

Proper Implementation of Resource Leveling

The Contractor wants to see which activity was delayed by predecessor or by resource; resource critical path provides the answer visually on the spot, on every screen.

From the next link:

Resource Critical Path Approach to Project Schedule Management

“True critical path should take into consideration all schedule constraints including resource and financial limitations.”

Nothing, new, we know that, our software developers do not know how to get the resource leveling algorithm to tell what it did. Our software developers are going backwards, re-inventing the wheel, hundreds of definitions for date fields and a database with thousands of irrelevant fields but not much up-to-date functionality. They are a bunch of database managers incapable of any scientific thinking.

Best regards,
Rafael

Hi All,

Allow me to refer to Mike’s post no. 16:

1. "Are you saying that you arrange your work so that rebar fixers - electricians and plumbers are all working in the same place at the same time? I don’t think so".

2. "The rebar fixers will complete the bottom section and move on - the conduit fixers will follow and then the rebar fixers will return for the top layer."

For No. 1 (If I’m allowed to answer), I’d say yes! This always happens before concrete placement and you are running after the inspectors to sign your pouring request!

For No. 2 - Ideal but not always the case, because conduit fixers tie their conduits on top layer bars sometimes (Mike, I thought you are a Builder???).

cheers!

Hi Anoon

Thanks for joining in.

Point 1.

I agree that sometimes things are a scramble and everyone piles in to get something done but this is not ideal.

I would not advocate setting up a programme which reflects a scramble before it becomes necessary - that only causes the scramble.

Point 2.

I chose the example of the mid point conduit because it was the most complex sequence.

BTW - I read about the floods - I hope you and yours are not affected.

Best regards

Mike Testro.

Thanks Mike,

I’m Ok (my family too), but I’m away (you know, trying to make money).

Point 1 - I believe it’s not a scramble. You schedule the crew on a daily basis, so if the works happen a day or a period before concrete placement, it’s natural that you need the skilled workers at the same time (regardless of the sequencing that you made in your plan). Nobody is scheduling on a minute basis at site.

Point 2 - For electrical conduits (i.e for floor mounted fixtures), workers will always tie the conduits and boxes on top layer bars to expose the boxes easily once they do the concrete chipping works.

By the way, I don’t load resources in my schedule. I only do it in my resume (to impress the probable employers that I really know resource scheduling).

I also don’t have any idea about resource leveling.

cheers!

Vladimir

Can Spider Project handle multi-constraint scheduling?

I have particular interest in the modeling of time-space conflict problem.

With increasing pressure for shorter delivery schedules, general contractors must increase the amount of work done per time unit by increasing the resources utilized by activities and by scheduling more activities concurrently. Since space is limited at many construction sites, an increase in space occupation per unit time can result in time-space conflict in which one activity’s space requirements interfere with those of another activity or with work-in-place.

The following is a reference to the above issue.

Everyone piles in to get something done

Best regards,
Rafael

… at some point Spider Project will be under check mate. LOL

Hi Rafael

I looked at your link - this is a typical passage:

A clear advantage of using GA over other methods is potential to locate global optimum or near global optimum solution without a necessity to search for all solution spaces.
Moreover, the processing time only increased as the square of the project size and not exponentially.

Please explain.

Best regards

Mike Testro

Mike

Easy, the principles of “survival of the fittest”, just give me the tools, whatever as long as it is close to the optimum, the same goes with Resource Critical Path.

The author most probably figure it out from observation on the required iterations as project size increased (I understand relevant activities count).

I just want to see with what does Vladimir is going to throw at us, if he says and can prove Spider Project can handle this then we should ban him for 30 years until our software developers can catch up.

Best regards,
Rafael

Hi Rafael

I have no idea what you are going on about.

Best regards

Mike Testro.

Mike

“A clear advantage of using GA over other methods is potential to locate global optimum or near global optimum solution without a necessity to search for all solution spaces.
Moreover, the processing time only increased as the square of the project size and not exponentially.”

Exponential functions look somewhat similar to polinomial functions you have seen before, in that they involve exponents, but there is a big difference, in that the variable is now the power, rather than the base. Previously, you have dealt with such functions as f(x) = x², where the variable x was the base and the number 2 was the power. In the case of exponentials, however, you will be dealing with functions such as g(x) = 2^x, where the base is the fixed number, and the power is the variable.

This is not a “Brute Force Method” that looks for all possible combinations and then picks up the solution but an algorithm that converges to the solution or near optimal solution substantially faster.

Our software are not keeping up with the available knowledge, our software developers are incapable of handling these solutions to solve real life problems. The issue on limitation on space is quite common, but how can you model this using available resource constraining functionality within our software? We got to stop thinking like if 50 years ago.

Spider Project is ahead, I want to see by how much.

Best regards,
Rafael

Hi Rafael

Are you talking about too many tradesmen working in the same workface?

Going back to the example of the Rebar fixers working in conjunction with the conduit installers.

You do not need fancy algorithms to work out how the two resources can be planned to work in conjunction.

It would seem that the rebar fixers are the driving resource and the conduit fixers are on standby to come in when the opportunity arises.

Say there is a resource factor of 80/20 Rebar to Conduit fixers.

I would set up the resource modelling for the rebar fixers of a gang size of 8 with an 80% efficiency rating.

That will drive the duration of the rebar fixing.

Above that I would set up a summary bar and allocate 2 conduit fixers on a non modelled resource on standby basis.

This will give both the resource histograms on labour deployment and cost.

Next question.

Best regards

Mike Testro

Hi Mike,

You said you only use hours as your "resource". And you are modeling it based on costs? (i’m not sure, maybe i’m refering to the other thread).

Since this thread is a challenge to you, I hope you won’t mind if I’m trying to dig-up the consistency of your statements (regardless of the threads).

You also said you can use several calendars provided the relationship is nailed to finish-to-start (FS). This I intend to agree.

Now the questions:

1.What do you think is the driving calendar, is it the task calendar or the resource calendar(s) (if you got day shift and night shift)?

2. Or do you need to assign a task calendar for a task that need several shifts? Or you are going to use only resource calendars?

if you just don’t mind answering

cheers!

Hi Anoon

Q1. The driving calendar is the task calendar.

In my simple bottom up FS method each task has:

1 Calendar 1 Resource 1 Work Pattern 1 Code.

I never put more than 1 type of resource to a task and the resource modelling software links the the task calendar to the resource.

If I change the task calendar the resource picks it up automatically.

In this way more than 1 calendar can be attached to the same resource in different locations depending on what the task has.

Q2. I think the above answers your question.

Best regards

Mike Testro

Mike,

1) Are you talking about too many tradesmen working in the same workface? – Yes, several crews working at the same time on the same limited space.
2) You do not need fancy algorithms to work out how the two resources can be planned to work in conjunction. – Yes, it is an advanced operations research question that is solved using fancy algorithms or by modeling all possible outcomes.
3) It would seem that the rebar fixers are the driving resource and the conduit fixers are on standby to come in when the opportunity arises. – is not as simple as that, it is a multiple constraints issue where resources are analyzed in conjunction of other constraint sets, space is a constraint set (type) different to resources that cannot be analyzed in conjunction using our old software, our scheduling tools and techniques are fragmented and designed to deal with a limited set of construction constraints.
4) The issue cannot be solved by considering available space as a resource, but as a different set of constraints.

Assume you are to retrofit a floor in a hospital, there are 60 rooms of different sizes and different activities to be performed on each room with many trades working at the same time; assume you have somewhat limited resources and at the same time a space constraint that varies from room to room. How to model this into a CPM to obtain the best on near to best plan would be a common question.

Many of us use resource leveling, a few true resource smoothing (not available in P3) without knowing the workings of the sophisticated algorithms, we don’t have to; all we need are the tools.

Best regards,
Rafael

Hi Rafael

About three years ago I was given the job of programming a refit of a working hospital - Great Ormond St - where wards and theaters were to be taken out of service in sequence and fitted out in a rolling schedule.

The rest of the hospital had to be kept working and if we missed the schedule then children would die - no pressure then.

A bottom up FS cascade for each trade was established for EACH ROOM and linked by:

1. Availability of Resource.
2. Access Allowed to room.

The project never went ahead because of lack of funds.

Best regards

Mike Testro

Mike

If you are referring to bed wards then after a few rooms you would get to the top of the learning curve and be able to adapt your schedule, on the other hand if work was to be done at areas with multiple room uses, each with different available work space, different trades requirements this would have been quite a challenge, no time for learning curve, you had to make it at first try on every room, a scheduling job only for very experienced planners.

In my sample question you had the whole wing available but trade coordination and limit of space still a challenge.

Best regards,
Rafael

Hi Rafael

I was a challenge - which is why I was asked to do it.

In a way I am releived that it never went ahead.

The rooms were all different sizes and uses - for instance a 3 bed accute recovery ward was different to the clean linen store room.

I had a lot of consultation and collaboration with the respective trade packages - particularly M&E.

Best regards

Mike Testro.

Hi Rafael,
sorry for the late reply. At the moment I train our customers in Germany and have some problems with Internet access.

You asked:
Can Spider Project handle multi-constraint scheduling?
I have particular interest in the modeling of time-space conflict problem.

Yes, of course. Though these constraints are rarely used in pure construction projects they are necessary for planning works at the shipyards and similar kind of construction.
Spider Project simulates material supply and material consumption. Spider Project levelling options include taking into account material and financial constraints. So activities that require materials that are not available are delayed. Space can be simulated as material. Construction crew (or ship part) require space (assigned as the special material) and finishing the work it releases space that may be used by other crews (parts). Very simple.

Spider Project Demo includes an example of material levelling. Construction project in Demo has limited wall frames and some activities are delayed until necessary frames were released if to run resource constrained scheduling. So I do not need to prove, just look at the sample project in Spider Demo.

Best Regards,
Vladimir

Vladimir

Let’s see if I got it. I can assign to each activity, to be performed within a limited area, a "space" material resource for this area, for other areas a different "space" material resource and in this way I can perform my multiple constraining for all "space" material resources and other resource types.

Quite ahead of what we are using!!! Our software has very limited capabilities with regard to multiple constraining. Some of these are performed independently of each other so you do not get the simultaneous constraining for all constraint sets with all the implications this mean. About financial constraints none is considered.

My son has a phone that can receive e-mails with a touch screen that rotates the image as needed, to me still a toy, a gizmo, we embrace this futile technology but for serious work we are still thinking in CPM of the 60’s.

Best regards,
Rafael

Hi Rafael.
You got it right.
Each area has limited space and starting to work in the area resources consume space material and finishing the work in the area they release space. If the remaining space is not sufficient activities and resources that require this space are delayed.

If you will compare current and "old" PM software you will find that new releases have a lot of whistles but the same or even less powerful engines. I hope that you and Mike will pardon me but I cannot understand why an ability to place multiple activities on the same line can be discussed as the serious advantage of some software. Yes, it is nice. But we estimate the software by the schedules it produces. If the schedules are shorter the software is better because it saves money and time. But it works for those who believes in resource levelling. And I don’t believe in manual levelling. At least it will be far from optimal and very time consuming.

Best Regards,
Vladimir

Vladimir

An ability to place multiple activities on the same line I do not consider it as the serious advantage of some software, is kind of a gizmo I like for convenience in report presentations for multistory buildings schedules, is a matter of convenience.

But the functionality for True Critical Path that Spider Project has, this is a must have, not being able to see driving logic (relationships and resources) is crazy.

I do not believe in manual resource leveling but with our software lacking the functionality for true Critical Path we have no other option than use soft dependencies to mimic true critical path. And yes we know resource driving relationships move, appear and disappear as the schedule moves. Soft dependencies are far from perfect, very far, we know.

Most of our contractors are small and not in the opulence as the big players, a few P3 licenses and the service contract for a few years would buy you a backhoe, we use SureTrak because of its price and compatibility with P3 and also because it is commonly specified or accepted as a substitute to P3. For your knowledge SureTrak was priced for about 400US$, street price on the internet, until Primavera/Oracle decided to raise the price of a product they no longer update.

Best regards,
Rafael

Spider Project is more expensive but it saves a lot of money to its customers. Actually it is a range of products from rather cheap Lite version (450 Euro) to expensive Spider Project Professional (€2800).
Lite version is rather functional (resource constrained schedule optimization, any number of cost components, trend analysis, etc.) but it does not include unique advanced features like material levelling, risk simulation, simulating working in shifts, portfolio management, etc.
We usually recommend Lite version to IT people. Construction projects are more complex and require more advanced tools (Desktop or Prof versions).

But Spider Project is cheap because our customers get Spider Viewer (special version that does not permit to change project data but produces any analysis and reports) for free and can install it on any number of machines. So there are a lot of people who have an access to project data even if only one license was bought.
It improves project management culture in the organization and we are interested in the proper use of our software.

Best Regards,
Vladimir

Vladimir

SureTrak was about 400US$ street price a few years ago when we got our licenses. Now it is about 800US$ the same version, just Google it. We got to love Primavera, with time vintage cars cost more, why not vintage software?

Best regards,
Rafael

Dear All,

I cannot imagine (forgive me I don’t really have an imagination) where this "resource leveling" necessary? Is it only for huge or big projects, or including the smaller ones?

For example: A small company got a contract to build a small electrical substation building and hired tradesmen as follows:

1. Steel Fixers - 6 no.
2. Carpenters - 6 no.
3. Masons - 6 no.

The company scheduled to complete construction in three months, do the company needs to level the resources mentioned above so that it can terminate 3 carpenters after a month? Or it will retain them for the next two months? How does a small company do his budget?

I believe the same will apply to big companies having smaller jobs but with higher quantities in different locations. For example, a thousand small substations in a thousand different locations.

cheers!

Anoon

There are not fixed rules, it depends on the particular needs of your work, the scale or granularity required to efficiently manage your schedule.

For your particular example, in our jobs the construction of the electrical substation building would require a small activity count but the masons would be taken from a pool of masons that might be scheduled to do work on other areas. Resource constraining helps you detect and avoid conflicts in scheduling activities when there is a shortage of resources.

If your company is doing just the substation building whether you use or not resource constraining the duration of the job will be driven not only by sequential logic but also by the assigned resources. Even after all this B.S. I would not take the time to model resource leveling in such a job and hire jack of all trades, expert in none but that can handle multiple trades.

The rule is, there are no fixed rules.

Best regards,
Rafael

.... Pacquiau, Cotto time is nearing.

Rafael,

I agree, "there are no fixed rules". Pacquiao is an example of it. Now I suggest that you place your bet in favor of Pacqiao.

A little history...he worked as a construction worker (peon), before he has established his name in boxing, so construction works made up his endurance.

I supposed he doesn’t know anything about scheduling softwares, but I’m sure that he knew how to make 30 million dollars in 30 minutes.

Now, the disaster that hits Manila adds to his inspiration.

Think about it, you still have time...

cheers!

I bet for Pacquiao.

50 USD if he will fail to win against cotto may go to your favorite foundation for the needy.

50 USD to 0.

Thank you,
Scarlett

Anoon,

We know about the disaster and wish your country well; we also know Filipinos are social people and even in adversity find a way to enjoy the little good things in life.

I will make a toast to the winner with my Empire State shot glass, one of my favorites in my collection, after the Mexican shot glass, the count is easy, just one.

Scarlet,

It is a deal, you are free to increase the odds.

Best regards,
Rafael

About levelling.

Proper levelling will supply you with the information about the minimal number of different resources necessary to finish the work in three months, when and what number of resources shall work, what materials are needed and when, if material supply has some limitations how to organize the work taking into account these limitations, etc.
Usually organization resources are limited and resource levelling shows how to do the work with the limited resources that you have, what order of activity execution to select to minimize project duration.

Regards,
Vladimir

Vladimir,

I agree with what you said.

When you are making a Plan or Schedule:

1. Isn’t it first you need to determine the activities?
2. For me, second would be quantifying the works or activities (with measurable units as possible).
3. Third would be determination of "Resources" to work on each activity that you had defined (if so).

Questions:

1. How can you level resources on Lump Sum activities (supposing its not possible to assign measurable unit on it)? - Assuming you are using a program or software.

2. Assuming you have a "resource pool" (as Rafael said), isn’t it evident that you can quantify a certain resource or crew in the first place before you can assign it to a specific activity that you had defined?

3. Now, supposing your project is offshore and you had scheduled a specific crew to work for two months straight, and mobilization/demobilization is not cheap, are you going to recall the crew once you had anticipated a delay for two weeks to happen and your crew would be on a standby mode?

I believe the answer is obvious, what I’m trying to say (if you’ll just allow me) is that,...anybody knows...???

cheers!

Mike,

I supposed nobody wants to challenge you anymore as regards resource levelling and your finish-to-start 0 lag relationship. With my limited knowledge (if any), I’m 100% with you.

Now, why you will do "resource levelling"? It is one of the many ways to make Profit.

Another question: How are you going to budget your "resource pool" say on a yearly basis (regardless if your company is big or small)?

Isn’t it still on a project basis? If you got project, you need resources; if you don’t have project, are you gonna get rid of your resources? Or sustain until your capital gets drained?

cheers!