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duration calculation for activities

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Mohammad Abdul Ba...
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hi i wanted to know how to calculate the activity duration
plz help...

Replies

Nahush Jain
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Hello Gents,

How about calculating the actvity duration through reverse methodology, wherein you have the contract value and labor or subcontract budget ex.HVAC trade > Calculate the total manhours required > With the available productivity rates, calculate the activity duration for HVAC subtrades like duct,chw etc 

Although not a accurate method, but it will help in budget check, trade specific durations & a easy format to be build and maintain. Feedback please ?

farnas ap
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Calculating duration is the key thing needed for a planning engineer,otherwise planning cannot be done or no one call that  person as planner he is just like a project engineer or else.

calculation can be done mainly as

the availibilty of resources

for eg

for 1 Activity 10000 bricks needed

we have 5 workers and productivity of them is 100 bricks for 1 hour(assume 8 hr per day)

Duration for that activity=quantity required for that activity/standard productivity of workers to complete that job

=10000/(8*100)

=13 days approx

if 10 workers are there it can be done with 7 days(without any delay)

I know that this post is out of date but it will help to someone sometimes

Stephen Devaux
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Hi, Mike.

Actually, I consult Judge Dredd about DRED slightly less often than I consult Priscilla, Queen of the Desert, about drag.

And yes, I have been following Windies' adventures in England. England have an excellent team -- any team that beats Aus and India the way they have recently is very powerful.  WI, OTOH, have been in the pits for many years! But finally, we are showing signs of stirring from the dead.  As it is, we've done better than I expected -- relatively competitive, even.  And I'm looking forward to Sunil Narine's debut Test on Thur, and then the ODI series.  We might surprise some people the rest of the way!

But England hasn't had a team like this in about 40 years.  Good luck to them.

Fraternally in cricket,

Steve the Bajan

Mike Testro
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Hi Stephen

Do you ever need to consult Judge Dred?

Best regards

Mike T.

Hey - England seem to be showing the Windies how to play cricket - or hadn't you noticed.

Stephen Devaux
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There is one technique that I have used in order to get at the resource elasticity (i.e., how much an activity's duration will change in response to added resources). It is a second duration estimate: the doubled-resource estimated duration (or DRED estimate):  how long would it take if you had double the resources? For all of Rafael's flying activities, it would be the same duration. For other types of activities, reasonable answers might be about 50%, 60%, 80%, 95%, 100% [not at all resource elastic] or 200% [workers will get in each others’ way.]  Very occasionally, the DRED estimate might even be 10% of the standard estimate: one person will require 20 minutes to lift the table up the stairs, but provide a second person to lift the other side, and they'll do it in two minutes.

The DRED estimate is  NOT intended as a predictor of duration, merely a predictor of resource elasticity.  Perhaps an increase of just one skill, rather than a whole crew, would halve the duration. If so that's what we need to find out when assembling and optimizing a schedule.

If I have DRED estimates, once I have put together the "first pass" schedule I would see what activities are on my critical path and what their Drags, Drag Costs and DREDs are. Then I would work with the activity manager(s) to optimize the schedule by adding resources to activities with large Drags and productive DREDs.

Fraternally in project management,

Steve the Bajan

Sunil Babu
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Hi Senthil,

Your explanation regarding the matter was so apt..

Thanks and Regards.

Sunil

Rafael Davila
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Senthil,

If Productivity of one carpenter with one helper equals 10sm per day then; 50 carpenters and 50 helpers means the activity can finish in 0.20 days. Good in case you are in a hurry.  It means that by simply adding more resources you will always be able to finish on time.

Following the same thinking, if one airplane can get me to NY in 4 hours, then 4 planes can get me to NY in one hour. If you want to save on airplane costs then get 4 pilots on the same plane, it will fly faster.

Sehari is correct, It is all about crews, and crews are composed of mixed resources frequently a mix of people and equipment; you cannot blindly apply the rule at the individual resource level. You cannot look at productivity books for average man-hour productivity without looking at the crew composition. Load your activities using whole crews, using the productivity of the crew as a whole even if you assign volume production at individual resource level.

More often than not, to get increase in production per day you have to change whole crew composition, as for example pumping concrete at the rate of 60cm/hour will require you to use a 60cm/hour pump and a pump operator instead of using 1.5 pumps rated for 40cm/hour and 1.5 pump operators.

Of course, for long duration activities where you have a crew assigned a percentage of the time the activity lasts; by simply changing the assignment percentage you can solve the issue up to the point where it is assigned 100% then thereafter you will have to look for changes in your crew as a whole or even changes in logic.

It is wrong to model activity duration based on the assumption elastic crew composition will proportionately yield a correct prediction. At the most you can automate partial assignments up to a 100%, sorry but real life is not that easy.

Regards,

Rafael

Sehari Mohamed
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RATION  DEPEND THE TEAM

Sehari Mohamed
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hello all #

 HP=QT*Ration

 

thank you all

senthil
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hi...

activity duration calculated based on resources availability.

activity name : shuttering works for retaining wall

total quantity is : 100 sq.m

productivity of one carpenter with aid of one helper : 10 sq.m per day

so 10 carpenters and 10 helpers can complete the work within a day. the reqd. duration for the activity is one day. if the available carpenters is 5 nos/day means the duration of an activity should be 2.

 

-------------------------------------------

 

by

senthil

muscat

 

 

 

 

senthil
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hi...

activity duration calculated based on resources availability.

activity name : shuttering works for retaining wall

total quantity is : 100 sq.m

productivity of one carpenter with aid of one helper : 10 sq.m per day

so 10 carpenters and 10 helpers can complete the work within a day. the reqd. duration for the activity is one day. if the available carpenters is 5 nos/day means the duration of an activity should be 2.

 

-------------------------------------------

 

by

senthil

muscat

 

 

 

 

Gary Whitehead
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For procurement activitites:

The intermal procurement processes (issue RFQ, Bid Evaluation, Award PO, etc) are fairly standard and durations shouldn’t vary much from project to project

The supplier activities (vendor data & ex-works) are much more variable. Until you start issuing RFQs, suppleirs often won’t want to put too much effort into giving you accurate timescales, and varying market conditions can have a big effect on delivery times, so data from previous projects can be of limited value. An experienced Procurement Manager who knows the market well and has good contacts with suppliers is invaluable.

Shipping to port durations are fairly standard and a quick call to a shipping agent will usually get you what you need.

Trucking to site can be calculated up front, but you need to know or make assumptions on things like #trucks per convoy, # convoys per day, local regs on max distance / time per day per driver, material qty per truck, truck average speed (very much depends on quality of roads), truck maintenance downtime, etc

If you’re crossing borders, don’t forget to allow time for customs


For design activities, if you have activity-based timesheet booking & a standard WBS you should be able to get reasonable historical data to base estimates on. I don’t, unfortunately :o(
Anoon Iimos
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Folks,

like Mohammed, I also want to know your comments or suggestions with regards to calculations for the durations of "Design Activities" + "Procurement Activities".

I may not like it if you just suggest to put "milestones".

come on please!?
Rafael Davila
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Mohammad
I tried to send you the following reference via personal communication in this site but unfortunatelly the system is down. It just came to my mind after my last posting.
http://www.gulfpub.com/
I believe Gulf Publishing Books are to the Petrochemical Industry what RS Means is for General Contractors in the USA.
Maybe you can adapt the information to your location.
Rafael Davila
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Mohammed
Although I provided a reference for the issue related to activity durations, in my professional practice I never used the "time-cost trade-off procedure" which as I said it is not even available in any Primavera Application. I don’t even know of anyone who ever used it. We have different needs depending on our particular projects, fortunately software vendors try to cover all the bases.
Because I read you are in the Petrochemical Industry I assumed you would be involved in essentially many parallel maintenance jobs. I believe that maybe the majority of your activities are inelastic due to space limitations, you cannot get 3 motor cranes, 20 welding machines and a 100 man crew to speed up work on a single distillation tower, and maybe you are limited to schedule a single crew per job.
Similarly in my Construction Jobs I cannot schedule Precast Installation with 5 cranes on a single location as space limitations and sequence of installation would be the limiting factor. I cannot schedule for the installation of the metal pans at will as the amount available for a particular job might be a fixed amount, in part determined by the particular structural requirements of the job. In this particular job, a School Expansion while the school is in use, we cannot increase at will some activities as we are limited in space to move around our hoisting equipment, production rates will not be elastic within these conditions.
Although usually over 90% of our activities are "inelastic" it is good to know you can use the software to apply these tools in case you are in need to adjust a few critical or near critical activities duration.
Eventually you will memorize your basic crew composition and production rates for most of your activities. If your maintenance activities are typical, let say replacement of a few valves and their actuators you will even be able to schedule most of your jobs by yourself. In my type of jobs I must coordinate with many different suppliers, subcontractor and trades, there is no way I can prepare a schedule and fix activity durations without getting others involved.
Stephen Devaux
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Gary, thank you very much for your input. For the record, Mike, I too think that lots of threads on the same subject are extremely problematic for discussion forums.

Both the thread topic and the the total content of the initial post ("hi i wanted to know how to calculate the activity duration plz help...") raise a topic that could generate answers in a wide variety of directions. I can imagine responses that would discuss parametric estimating, the benefits and shortcomings of three-point estimating, bottom-up estimating, or even estimating of remaining durations on activities that have started. All of these would have been on-topic responses.

It should not be up to any PP member, including moderators, to censor civil, knowledgeable, and on-topic posts. And I am confident that the end of your last post was not intended to suggest that you would feel empowered to "interfere" with posts or posters whose discussion tastes are different from yours.

Now it would be best if this thread returned to a discussion of activity duration calculations. Let’s keep it on-topic. As Gary suggested, if anyone wants to continue this meta discussion, please do so in the Improving PP forum.

Fraternally in PM,

Steve D.
Gary Whitehead
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Mike:

1) Moderators can’t set up new forum categories, only PP Admin.

2) Having the same topic discussed in multiple threads is the bane of many a forum. Readers would have to search through different threads in different categories if they wanted the full range of PP opinions on a given topic, which is a bad idea IMO.

3) I am not clear on how Stephen’s post denied you or anyone else "the chance to get on with the task of offering practical help to people who need it"?

In any event, we apear to have hijacked this thread somewhat. May I suggest if you have any more thoughts on the subject, you create a new thread in the ’imporving PP’ category?

Cheers,

G
Mike Testro
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Hi Stephen

OK May I suggest a way forward.

You are a Moderator.

Why not set up a Forum Category entitled something like "High Planning Principles" where those who operate in that stratosphere can communicate with each other at Peer Level.

This would leave the rest of us who are grubbing around in the basement for a living the chance to get on with the task of offering practical help to people who need it.

You could copy any thread to your forum category for discussion and the rest of us would be grateful to visit and to see what we are missing.

I promise not to interfere in your discussions unless it is absolutely necessary.

Best regards

Mike Testro

PS who have you got your money on for the 20-20 series in South Africa?
Stephen Devaux
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Hi, all.

Vladimir, I guess I was asking if Spider users avail themselves of the project value and profit functionality. Not only is such functionality rare (or very limited) in other packages, but I suspect most users wouldn’t have much clue nor desire for using it. At least in my experience across many applications, projects continue to be seen and measured in terms of cost (witness earned value indices!) rather than the more important value and profit. I’d be curious if other non-construction folks also have this perception.

Mike, decades ago I read of a wonderful Russian proverb: "Chess is an ocean in which a gnat may sip or an elephant swim!" I humbly believe that this should be the model for a forum like PP.

Surely there is room here both for those who are interested in fundamentals and for those who would like to converse about more complex subjects? Any readers of Thoreau, specifically, and many other essayists, will know how even a paragraph that starts with the mundane can trigger ideas that invoke the sublime.

Those PPers who wish to sip of only one beverage should be able to do so; but those who wish to wallow in all flavours should also have that right. And when faced with posts of an unfamiliar flavour, those who prefer to always order "The usual, bartender!" may choose either to try a taste or to avert their faces.

What they do not have is the right to shout down those with different taste buds. And I happen to think Raphael put it perfectly when he posted: "Mohammad please don’t be intimidated by the language of the trade if you dont know it, sooner than latter you will have to scope with it."

The Pharoahs may have managed projects -- yet project management as we know it is a very young discipline. We, collectively, are its midwives, and we need to nurture it with both advice and training for new practitioners AND with new ideas. WBS, CPM, EVMS were all once unfamiliar acronyms. So too new ideas/metrics like ABCP (totally unknown in most PM applications!), DRAG and DRED may become standard, but only if people learn about them. Those who choose not to expose themselves to new ideas are free to do so. But I, for one, am committed to improving our discipline. Too many people die because of poor project schedule management. If you don’t believe me, try Googling: "Dhahran" "Patriot missile" for just one example.

Mike, your experience in and knowledge of construction PM is profound, and very helpful for most readers, including myself. PP started as a construction project management forum, and there is still a strong flavour of construction management. But there are now also a large number of members from Oil & Gas, Defence contracting, IT and software, and even pharmacutical and medical devices. All these have industry-exclusive ideas about PM that can often be cross-pollinated. We can choose to be a big tent or a small tent. As far as I know, PP Admin has not weighed in on this; but as it has accepted members from all these industries, I assume it has opted for the big tent, with many rings.

As to my name, I served as a lowly enlisted man in the US Army. I therefore have been called many, many names, often consisting of four letters and often in an Alabama-to-Texas accent. I therefore find it easy to ignore the bait of mis-spellings of my name.

Fraternally in PM,

Mike Testro
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Hi Stephen

Thank you for your gentle admonition on my choice of language used in my last but one thread.

We have discussed the use of acronyms and complex theories before and I have no doubt that there is a place for them in the higher realms of planning practice.

At the work front however the planner has to do the best he can in the time available and that is why I advocate the simplest and clearest method set down in plain language - in my case English.

In other threads I have set down the method I use for resource modelling which takes me about a day to complete from Cost Plan to Resourced programme.

Vladimir and I had a lively exchange recently on the benefits of software resource levelling which I beleive ended in a mutually respectful draw.

My position remains however that resource levelling may work in sohisticated software such as Spider but it doesn’t in any other platform that I have come across.

Best regards

Mike Testro
Rafael Davila
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Mohammad maybe you know all the language of the trade, maybe you don’t; either way, your question is relevant at every level judging from the response of Mr. Devaux and Mr. Liberzon. Mohammad please don’t be intimidated by the language of the trade if you dont know it, sooner than latter you will have to scope with it.
Activity durations is manipulated, sometimes by default, differently among the available software packages. Microsoft project use the term Resource Driven while Primavera P3 and Suretrack use other terms. These options will become relevant at your first schedule update, here you have the options of resource leveling or resource smoothing which might yield different results. Also these options might be relevant when you convert file formats, you might be surprised by unexpected manipulation on activity durations unless you are in control.
Mike I believe Mr. Devaux first name is neither Steven nor Stephan but Stephen.
Hi Stefan,
all Spider Project users that we know use this functionality. Spider Project implementation always starts with creating corporate reference-books on cost and material requirement per typical activity volume units, on resource prouctivity on typical assignments, standard multi-resources (crews), etc.
And then creating the library of typical fragnets - mini-projects describing typical project processes.
Only after that corporate PM system may be created.
Regards,
Vladimir
Stephen Devaux
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To Rafael:

I agree that there is no quick fix -- but there are processes in optimization that software can do rapidly, but manually would require intensive and tedious effort. There is no reason in the world that, if a planner inputs an alternative duration estimate (I’d suggest DRED as a quick-and-dirty way of estimating an activity’s resource elasticity), the software should not compute DRAG and DRAG Cost, and show the project profit to be gained by using DRED estimates (or massaged DRED estimates) on specific CP activities. All the software would need to be able to do is:

1. Allow input of project value,
2. Compute activity DRAG, and
3. Compute increased expected monetary value and decreased LOE/overhead cost for a shorter schedule.

Which brings me to Vladimir’s comment:

It sounds as though Spider has some pretty amazing functionality -- a question: how many of your clients are using much of this? (If it computed DRAG, it sounds like Spider could do the whole nine yards of TPC. I hope we have the chance to chat at the Boston conference of the PMI College of Scheduling.)

And finally to Mike’s comments:

First, my sincere apologies for breaking the PP Forum rules. (I looked at the Rules to see where they enjoined posters to stick to the KISS principle and banned "high arcane textual gibberish". I’m not sure I found it. The closest I could come was Rule 2: "Keep conversations civil. This is a professional forum. Flaming, taunting, name calling, abusive language and derisive / condescending posts will not be tolerated." It was certainly not my intent, nor, I suspect, Rafael’s, to use words that some might interpret as being "flaming, taunting, name calling, abusive language.")

Thus my deepest, humblest, and most abased apologies to anyone for whom the discussion seemed to become too complex, and for going with Raphael "off with the fairies", or even Pharoes! (Or Pharoahs? Or Pharos? That must be it! I see the light!) And thank you, Mike, for pointing out my breaching of the forum Rules, written or unwritten.

Fraternally in PM,

Stefan D.

It is easy in Spider Project.

Initial information on activity duration may be Duration itself, Volume (Amount) of work to be done, events determining activity start and finish time (for hammocks or LOE), or an activity may represent milestone (zero duration).
If activity Volume is an initial information then project planner shall enter assigned resource prouctivities.
They can be taken from the known databases like RS Means and it is useful for Clients (or Buyers).
Construction companies usually create their own Reference-books with productivities of their resources on typical assignments. These Reference-books are maintained in Spider Project.
Besides it is useful to create another Reference-book for usual crews (gangs) of resources that are used on typical assignments.
If Project Planner assigned such crew or individual resources to some activity resource productivities can be automatically transfered from the reference-books.
For simple assignments activity duration is calculated dividing activity Volume by total productivity of assigned resources.
In more complicated assignments activity duration is calculated during scheduling.
These complicated assignments may include:
1) assignments of different crews in different shifts. In this case activity duration may be calculated only when the time of activity start became known,
2) variable resource assignments when project planner defines minimal and maximal number and workload of assigned resources. In this case the number of resources that work on activity can change in time,
3)skill assignment - in this case the software selects which resources that have necessary skill to use. Resources may have the same skill but different productivities.
It looks complicated but for the software and not for the project planner. It is enough to enter activity and resource types. All the rest will be taken from the corporate databases (reference-books) automatically.

In corporate project management system it is necessary to define corporate norms. Activity duration estimates shall be based on these norms. If these estimates are based on someone’s estimates it is hard to defend them, to analyze project performance, to keep knowlege databases, etc.

About time-cost trade-off.
Project cost include indirect costs that depend on the project duration. We recommend to include these indirect costs in the project schedule model.
Besides, the project can generate future earnings. In this case we recommend to add to the project model activities that simulate these earnings and start after project finish. It does not make sense to simulate the whole product life cycle, so profit activities shall finish at some predefined date.
In this case you will be able to manage not only project expenses but also project cash flow and estimate the influence of management decisions on project total profit to some date.
Another option - to define the cost of one day of project delay and simulate these penalties or earnings (if to finish earlier than expected).
Using these approaches you can adjust assigned crews to achieve better results by automatic time-cost trade-off.
Optimizing cost you select the best project duration and resources to be used.

Best Regards,
Vladimir
Mike Testro
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Hi Stephan

Sorry I spelt your name wrong in the last thread.

Best regards

Mike Testro
Mike Testro
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Hi Rafael Hi Steven

What are you going on about.

This high arcane textual gibberish has no place in day to day project planning.

The poor guy who started this thread just wanted to know how to generate durations.

I tried to tell him a simple method and then you two are off with the fairies - or is that the Pharoes?

Please in future employ the KISS principle.

Best regards

Mike Testro
Rafael Davila
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I believe the nonlinear behavior; either due to diseconomies of scale, either due to the learning curve or due to any other reason such as space limitations can be modeled using a technique I studied 31 years ago. It was available in some software packages; it was called “time-cost tradeoff”. These software packages modeled this behavior not as a single or two points but as a continuous function. A reference could be the book by Moder and Phillips – Project Management with CPM and PERT, latter revised and renamed to include the term Precedence Diagramming in the title.
I know the cost can be modeled but with resource constraining/smoothing at the same time I wonder as I never had acces to these software and no Primavera software has these options.
Preciselly because of the validity of your argument we keep duration of activities fixed, then if needed to comply with contract time, we manually adjust activity duration and resource loading.
Yeap there is no quick fix.
Stephen Devaux
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One further technique that might be of help is an alternative duration field for the DRED, or Doubled Resource Estimated Duration. DRED is a way of estimating a quality, "resource elasticity" that everyone knows activities have, to a greater or lesser extent. But rarely is this quality quantified.

When Mike wrote...

"For instance if you have a wall that has 10000 bricks and a gang of bricklayers can lay 100 bricks an hour then the duration would be 100 hours. 2 gangs would take 50 hours."

...he was suggesting that building the wall is "perfectly resource elastic", i.e., doubling the resources halves the time. That’s true for a lot of work, and it’s nice when it happens -- but it is often not the case, especially outside of construction.

Doubling resources on a 100-hour duration activity can:

a. Reduce the duration to 50 hours (perfectly resource elastic, and thus with a constant hourly rate results in no cost increase).

b. Reduce the duration to 60 hours (perhaps very helpful, but increases work hours to 120, and thus increases cost).

c. Reduce the duration to 80 hours (a slight improvement in time, but purchased at a cost of 160 workhours).

d. Leave the duration unchanged at 100 hours.

e. Increase the duration to 140 hours (as would have happened on a project I consulted on a few years ago to assemble avionic controls in a jet fighter cockpit -- more resources would have gotten in each other’s way. Many software projects are like this also, thus leading to Fred Brooks Law that "Adding resources to a late software project makes it later.")

The DRED is important info, both for upfront schedule optimization and for later, if the critical path starts slipping. For example, if a 20D activity has a labour budget of $100K, DRAG of 12D, a DRAG Cost of $20K/D, and a DRED of 13D, doubling the resources will increase the labour cost to $10K X 13D or $130K, but reduce the DRAG Cost by 7D X $20K = $140K. Planned project profit would thus be increased by $140K - $30K = $110K.

Fraternally in PM,

Steve D.
Anoon Iimos
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"duration calculation for activities"

I supposed these are the usual practice (using planning tools or software):

1. A Planner (Old or New) will type the activities.

2. After typing the activity description, the second thing in mind is to type the duration (this is supposed to be the Original Duration or OD). What brainstorming, resource modelling or reference for productivity rates? You never got time for that! The time will come during execution, where the real works will come in. At these times, All are Planners (or wanting to be), but never during the initial development of the Plan.

Common folks, be real!

i’m not real

Mike Testro
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Hi Rafael

You are quite right.

Keep learning and - if you don’t know - ask someone who does.

I have been doing this all the time over the last 45 years in construction and people who know are delighted to share their knowledge.

Come to think of it this is what PP is all about.

Best regards

Mike Testro
Rafael Davila
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You can control your Activity Duration deppending on your available resources, the controlling resource does not necessarilly deppends on manpower it can be equipment production rates.
Your first reference should be your contract requirements, then your company estimator. Look for refinement and team buildup with the job Project Manager or Superintendant, make them part of the schedule, ask for their comments and suggestions.
Also your Company records on Job Costing should validate the assumed production rates which your estimator might have adjusted to your specific job. Preferably use crew production rates avoiding the use of fractional crews.
Your last resort should be production rates books as production rates will vary deppending on the job location. Your rates books should show you what is and what is not included and equipment or thechnology used.
If in the US you could use RS Means for General Construction but should look for books specifc for your industry.
As Mike says there is no quick fix. Maybe you will get a better schedule than those of us who wrongly belive know everything and forget about the most usefull management tool "Brainstorming".
Mike Testro
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Hi Mohammad

Sorry to say there is no "quick fix" od shortcut to what is a fundamental part of programming.

You will have to do it propperly from first principles

Best regards

Mike Testro
Mohammad Abdul Ba...
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Thanks Mike for your assistance i wanted to know any standard guide or procedure manual for quick reference quide...

regards
Mike Testro
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Hi Mohammad

You need to use the resource modelling software in your system.

Basically most types of software have a resource modelling section which works on the basis of the amount of work to do set against the number of workers available to do it.

For instance if you have a wall that has 10000 bricks and a gang of bricklayers can lay 100 bricks an hour then the duration would be 100 hours. 2 gangs would take 50 hours.

The trick is knowing what the production rate is.

Best regards

Mike Testro