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Does anyone can guide me regarding some international norm on allowable/safe"manpower density" at construction site? Specifically I am looking for the ref which tells me that if I engage more than X nos of manpower over Y sq m of construction area, it will not be safe and my productivity will reduce.
Thanks,
Mayukh
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Normally Size Of Toilet OF Commercial Flat will be around this size or less 2.Mtrs *2. Mtrs
an area of 4 Sq Mtr ,
normally i put 1 Mason and One Helper there, but when thigs are urgent put 2 masions and 1 helper
How the logic of 25 Sqm per men applies here
When planning an industrial project I start with 250-260 sf/man or about 25 square meters. From this starting point I adjust this area for vertical construction, not multi floored construction but whether there is overhead work, pipe racks, suspended ductwork, large process skids, etc. The more tasks required in the same space the larger an area required for each man.
I do not use this # to assign the number of workers, just to calculate the point at which productivity and Safety will be affected.
10000 sf area = 40 men that can be effective. If the work in the area is installation of process skids, pipe rack and ductwork then the effective manpower would reduce to about 20 or 10000/500 sf/man
The 500 sf comes from a judgement call based on the particular project constraints.
There is no mathematical way to determin a "safe #" when it comes to safety. Each task needs to be anylized for hazards. However it does follow that the more people are crowded in on a construction site the more unsafet it will become. Therfore a higher density site can result in more incidents.
When setting up a project I reduce productivity porportionally when the density is above 250 sf/ man. If the density is greater than about 400sf/man I think about shift work and adding more safety supervision. (At high density levels overtime does not reduce the density or increase productivity, just increases craftsman frustrations and the potential for an accident).
These are rules of thumb from a company I worked for years ago. They have worked for me for the past 35 years for gross project planning. I have not seen them in any publication.
Hope this gets you started.
Mike,
If you are scheduling the construction of a cruise ship, you would perhaps have about 600 confined areas with several environmental constraints on each as a few zones won't do it, in addition you will have to correctly model shift work to determine duration of activities that span several shifts and you do not know in advance how much work is to be done on each shift.
Here you will need software that can correctly model shift work as it was previously shown by Vladimir many of the other software cannot correctly model shift work. He performed a very simple proof on a few activities sample job, but here you will have thousands. Manually adjusting shift work would be insane.
Are you going to model this by hand? Are you going to pre-define soft-links that will limit your resource leveling or are you to re-define the soft-links for every schedule run? If so make sure these soft links allow you to get optimum or near optimum resource usage.
Your fixation into only FS relationships and no resource leveling is blurring your vision. This might make it easier for the forensic analyst to prove cause and effect but at a very expensive cost to the job.
Best regards,
Rafael
Mayukh,
You need to use your own judgement, visit the site and evaluate the work they need to perform and the equipment they need to use, you can also get the opinion of the people running the job on site.
Regards,
Mike,
Even without the use of Material Resources, you can model environmental constraints. You can set available quantity for each environmental constraint for each area equal to 100, then assign environmental resource usage as a percentage for every activity and perform resource leveling.
As you can see from the following example for some environmental variables you shall assign a nominal amount as to prevent them to be assigned when others are assigned 100%, such is the case for available air. For economy of space I am not including other non-environmental resources. Yes, assignment of environmental resources is somewhat arbitrary, it cannot be solved using e=mc2.
In this way, resources will be assigned based on availability and not on faulty “soft” logic. In my example consider Epoxi Painting not dependent on Floors nor Ceilings, any sequential order might be acceptable, the constraint is on breathable air, that is, any other logic is wrong and might prevent adequate resource leveling. Very simple and all major software can do it.
Best regards,
Rafael
Mayukh
If you cannot find that magic and unquestionable book then you can still prove your case but it would be after the facts. The case you are mentioning is analogous to an acceleration case, and there are ways to prove it and quantify it. The most common is to keep production records for the beginning of the job for those activities in question, then if when the owner requires you to keep schedule even when the job was delayed because of his actions then you will have a solid comparison base to make your claim.
Perhaps you increase labor by 40% and get an increase in production rate of 20%, and suppose this allows you to finish on time. If the effort was needed to recover owner caused delays then you are entitled to the difference.
When it comes to recovering lost productivity costs, the least subjective, and therefore most reliable, method is the Measured Mile. This method distinguishes itself from other methods because it allows specific impacts to be isolated while accounting for other inefficiencies inherent in the work being performed. It is neither based on industry averages that may not hold true for a particular contractor nor does it assume that all inefficiencies are attributable to the Owner, as in the Total Cost method.
http://www.ce.berkeley.edu/~ibbs/BRICS/Materials/Ibbs_Liu_JCEM_2005.pdf
http://www.brianerawling.com/PDF/Dec%2004%20~%20The%20Measured%20Mile.pdf
http://www.warnercon.com/articles/AACE%202002%20Measured%20Mile.pdf
http://www.floridaroof.com/file-dir/Approximating_Damages_The_Measure_Mile_Analysis.pdf
Sorry, it is after the fact, in any case using industry average reference books will always be questioned, even your own records on other jobs will be questioned, on the other hand other, after the fact methods such as the measured mile applied to the job in question are widely accepted methods.
If you find a book that measures differences in productivity for variations in density for numerous construction activities I will call it BS (yes Bull Sh...), perhaps no one dares to publish such a book, too many variables.
If the owner insists on you increasing crew size, I believe the best you can do is explain the owner why it is not efficient to increase work density and make it clear it will have a cost impact you will latter claim and prove using widely accepted methods to determine productivity loss.
Best Regards,
Rafael
Thanks Mike, Rafael for your valuable comments...
But still I am looking for any standard/international norm (may be different for diff types of projects) for the manpower density. may be a specific norm ....
My actual issue is : If my project is delayed and i wish to have a time extension from Client, the argument I have to counter is that why I can not increase manpower/machinery and complete the job in time. from this point of view, I have to put an solid argument that beyond X nos workers/100 sq m area will be reducing the productivity and it will not be safe also.
Or any HSE guideline can give some clue on this?
Thanks,
Mayukh
Mike,
Bottom up cascade is in no way a substitute to resource leveling algorithms. Such a call is in abominable error.
In a single space, resources are competing to work either at the same time or based upon a sequential logic. The demand and availability of resources varies along the schedule timeframe and using soft dependencies is a rudimentary approach prior to the 60's, is archaic, is wrong, is obsolete. Your solution can provide a workable solution the same as if you schedule all resources to work in tandem, perhaps a single worker at any given time, yes workable but bad medicine. Will take you 100 years to build a 10ft dingy.
Get out of the Middle Ages and read a bit about modern mathematical algorithms, no need to understand everything but enough to use them. The same way I use my PC but know nothing about how it works. It is not that hard.
Is Asta capable of modeling resource consumption and resource creation? Based upon your posting I suppose it does not.
Best regards, Rafael 
Hi Mayukh
You are absolutely correct - too many operatives in a confined workspace will affect productivity - they will be tripping over each other and getting in the way.
So the answer is to work bottom up:
1. Define your workspace on the plan - this is usually set by access to the work front by both vertical and horizontal routes.
2. Once defined set the tasks to be completed within the worlkspace.
3. Set up the cascade of tasks to be completed within the zone.
4. Use your skill and experience as a builder to assign the correct number of people to complete the tasks. (If you don't know then ask soemone who does)
5. Complete your resource modelling for every task.
6. Press F9
Best regards
Mike Testro
Hi Rafael
So good to see you live and kicking back in the forum.
It seems that you have forgotten everything I have taught you over the years.
All you have to do is set up a bottom up planning system where every task is dedicated to one zone where a trade can work in peace before handing over to the next trade.
It is called a bottom up cascade and we have debated this many time over the years.
Forget your fancy links and resource levelling - proper bottom up planning is the ONLY way to do it.
Here we go again - all new members please pile in - I am up for it.
Best regards
Mike Testro
mayukh
Space can be a very limited resource that is 100% available when no one is working on a given area, as soon as more people get to work in the area it is consumed until no more people can work on the area, when people start leaving the work area it is then released or produced.
Very few software can model this with resource production and consumption, especially using what some call “materials” resources. I use Spider Project and have before debated the modeling of space as a limited resource under Spider Project Forum.
Keep in mind that people doing different operations might consume more space than others, it might even be that a couple of persons occupy all available space as is the case when epoxy painting a room, either others leave or use respirators. In such case, you might need to model for several definitions of space, say man-density, equipment density, environmental density (noise, dust, air). Then the driving space resource(s) will allocate adequate manpower level.
I understand that perhaps for the shipbuilding industry this is a relevant constraint that might drive the scheduling of most of your activities.
If getting reliable and unrestricted crew productivities is hard, getting productivities that consider these constraints will be harder. You shall look for the way these are taken into consideration for the actual scheduling of your jobs, then you shall tabulate the data for your models. Remember productivity reference books are based on averages for a specific region or country and my experience as estimator has been that they are not reliable and that at most to be used just to close a few missing cost items but never for the whole thing. Use your own company reference books, if you do not have any, better start creating your own.
Best Regards,
Rafael
I am looking for a norm as may be explained in the following way:
maximum "X" nos of workers per "Y" sq m of construction site plan area is allowable to have optimal productivity level as well as from safe working environment point of view.
In other words, if we increase the no of workers in that particular area beyond that magic "X" no, my production rate will decrese.
Hope I am now clear with the query.
Thanks
mayukh
kindly can u explain more, to able me understand what u need.
regards.
mai
Email: PPadmin@planningplanet.com
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