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Resource cost rounding

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Bogdan Leonte
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Hello Vladimir,

Materials in Spider have an option called Discrete Consumtion which rounds up the consumtion of the material (granted the Backload consuption is set to No).

So here is my question, is there a way to do this with resources?

Example: 

Backhoe is paied by the day even if it works for 2 hours or for 8. I would like to know if there is a way to take this into account when calculating costs.

Best regards,
Bogdan

Replies

Rafael Davila
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Vladimir,

My post is just a statement of agreement that granularity is frequently required. 

Skill assignment is not the same as partial workloads:

  • For elevated slab flying forms the two cranes are required to do work on section B as in some areas of section B crane 1 will not be able to clear slab perimeter and take out elevated slab forms.  In the sketch you can see a rectangle outside of the slab perimeter mean to represent elevated slab flying form, only crane 1 can get it out. The rightmost forms in section B can only be moved to next level by crane 2. The leftmost forms in section B can only be moved to next level by crane 1.
  • Wall forms for elevator shaft(s), usually at the center of the building, might be a heavy prefab for the interior faces; therefore because of their shape, weight and additional stripping force it is preferred to handle these with the crane that is closer. 
  • Safety is always a major concern when there is a possibility of crane cables colliding. A way to keep it under control is to have anti collision system and limit to 3 the quadrants each crane works at any given time. When working on section B the two quadrants the two cranes share can be alternated in coordination with the superintendent. This is another reason to plan 2 cranes with partial workloads.

Cranes-1-2 Moving-the-Flying-Concrete-Floor-Forms  Elevator-Core-Forms

Best Regards,

Rafael

Rafael,

I do not understand if there is a question in your post.

I don't see any problem in your scenario.

Just assign the skill Tower Crane to activities of section B.

Skill consists of two multiresources consisting of the crane and its operator.

Spider Project will select which crane to use on any activity.

Rafael Davila
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Vladimir,

I will be experimenting your suggestion, seems this is what I am looking for.

I would like to add I agree with your assessment about the necessity for discrete planning for some activities.  I believe granularity shall be what best fit the needs of your model.
 
I do not believe you can figure it out for the following scenario without discrete planning for resources and activities.  At times crane is reserved for a single activity at specific times of the day but at other times it is shared.  Crane 1 is needed for section A, both cranes are needed for section B and crane 2 is needed for section C.  Communicating such detailed planning is essential for planning as well as to train new field supervisors.

Work-Patterns-for-2-cranes   Cranes-1-2

Best Regards,
Rafael
 

Rafael,

yes set fixed volumes for assigned teams, set calendars for assigned teams, set resource productivity for resource assignments, create UDF for volume units and set them for team volumes, define material requirements for assignments (I prefer per assignment volume unit), set resource costs or unit costs or both.

In Spider Project you can create Resource Centers. I suggest to create Resource Center Labor and include there all labor resources. As the result you will get any report on the resource center including cumulative labor hours. 

Rafael Davila
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Vladimir,

  • Do you mean using multi-resources and volume fixed for teams?
  • How do you get hours for labor resources only? 

Maybe a tabular report will address both.

I believe controlling cost by looking at labor production rates is a very good approach.  Labor costs have the highest variance and on average represent 40% of the direct construction costs and this you can get at the jobsite with precise quantities on real time.

Best Regards,

Rafael

P.S. I do not want Spider to get too complicated with regard to these reports, I appreciate Spider Project for modeling remaining work, here it provides more than I ever needed, but I know if I ever need more it is already available without extra learning effort.

Rafael,

you can assign different volumes for different teams but it will be necessary to create UDF for units of measure.

Activity volume will be the sum and will not make sense but teams (resources) volumes will be right.

Material requirements shall be set for assignments (not activity!)

Look at

Teams

Rafael Davila
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Bogdan,

I am not interested in the distribution per activity, but a summary per cost code.  I am looking for budget labor production rates, current period labor production rates and to-date labor production rates; for hundreds of cost codes as shown in the following figure, showing two of the many reports for costing and production reports we are used.

Sample-Unit-Cost-Unit-Production-Report
 

  • Any activity out of hundreds or thousands can have multiple cost codes with distributions by LEMSO for labor, equipment, materials, subcontracts and other.
  • Same cost code with distributions by LEMSO can be assigned to hundreds or thousands of activities.

I do not find this approach practical, is too complicated, data entry looks to be a nightmare even when only for production reports.  When required to use other CPM software by client as it is common at home it is not transferable.

Best Regards,
Rafael
 

Bogdan Leonte
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Rafael,

you asked „When activity includes several volumes of work how can you get the current production rates for each team?”

Why not do the following:

Create 3 user fields (UF): Volume [UF], Unit of Volume [UF], Productivity [UF]. You can enter Volume and Unit of Volume at the Team level and then using a formula Volume / WorkLoadPlan (Resource Hours [Remaining]) and you get the planned productivity.

Also assign an insignificant Load (0.0001) to your 6am-8am, 8am-10am, 10am-11am resources in order not to influence your resource-hours column which is summed at the team level.

https://postimg.cc/cg6HXW8d

Using actual data you can get actual productivity.

Is this what you were looking for?

Best regards,
Bogdan

Hi Rafael,

now I understood your work pattern.

Here it is different. As I explained in my previous post the whole job is divided into divisions and pouring is done for the whole divisions only and this results in the necessity for discrete planning.

Rafael Davila
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In our regular planning for similar jobs, we pour concrete slabs each day early in the morning because of rain pattern and schedule them as individual activities, preparation for slabs take days and schedule them as individual activities.  For some locations we excavate footings early for 2 hours every day, then place reinforcing steel on whatever is ready and pour by mid-day whatever is ready as to avoid rain and not to leave open excavations during the night, we schedule them in groups as a single activity that spans several days.  We form walls using flying forms every afternoon and pour these walls late in the afternoon, we schedule them as groups, we schedule them as a single activity that spans several days.

I do not recall a single such job with 3 activities/day for each footing group, such granularity is unacceptable to my clients. Many go as far as rejecting resource loading.

I still wonder if excavation crew works 2 hours per day, reinforcing crew works 2 hours per day and pouring crew may work or not depending on the weather but if work then only 1 hour per day [then next day continue with 1 hour excavation to finish the required 2 hours, then 2 hours reinforcing steel and 1 hour concrete pouring].

I understood that your footing consists of several divisions that are done one after another, [Some divisions or group of footings are planned one after another but might be independent of other groups] pouring may be done for whole divisions only [pouring is done for a portion of each division each day until the division finishes], that excavation crews and reinforcing crews are different [yes they are different] and can work in parallel though at different divisions [we do not plan them as partial workloads so each crew work on only one division at a time].

Pouring crew can also work in parallel with others [we do not plan them as partial workloads so they work on only one division at a time] and requires less number of workers (variable assignments will be useful here) [resource quantities are fixed and at 100% workload, variable quantities and workloads is for activities that can use them when idle].

So we don't know the exact time when division excavating will be finished [within first 2 hours of last day of activity execution] and reinforcement may start [at 2nd hour of each day while activity is not finished]. We may plan that it will take 2 hours but in fact may take more or less [will take no more than 2 hours per day as per allotted time]. And so I don't understand resource assignments for certain time as in your example, for certain volume yes [each crew will have a specific time slot and next crew will work on what prior crew finished on that day].

Best Regards,

Rafael

Rafael,

I still wonder if excavation crew works 2 hours per day, reinforcing crew works 2 hours per day and pouring crew may work or not depending on the weather but if work then only 1 hour per day.

I understood that your footing consists of several divisions that are done one after another, pouring may be done for whole divisions only, that excavation crews and reinforcing crews are different and can work in parallel though at different divisions. Pouring crew can also work in parallel with others and requires less number of workers (variable assignments will be useful here).

So we don't know the exact time when division excavating will be finished and reinforcement may start, We may plan that it will take 2 hours but in fact may take more or less. And so I don't understand resource assignments for certain time as in your example, for certain volume yes.

I don't discuss contingency reserves, just planning resource work.

Rafael Davila
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My typical construction workday is 8 hours as shown in the provided schedules, it is footing activities that are planned to take 5 hours a day.  Because of our rain pattern we do not leave open footings overnight, for mat foundations we place 2in lean concrete base and an electic water pump to keep excavation dry.

No schedule goes exactly as planned therefore we plan with this contingency in mind, that at times it rains in the morning is a contingency we must consider.  Contingency planning can take many forms; can be added time to activities, this usually I do not like unless it is not significant.  Contingency planning can be having spare resources you do not include in plans such as having extra labor to account for vacations, unplanned work, sick days etc.  Targeting for early completion to increase probabilities of finishing on time is another contingency strategy, this is my favorite for construction works.  For other type of works adding activity time is not always a sin.

For footings pouring crews are laborer, anyone who can work a concrete vibrator can do it, these laborer then move to other activities just that in my example for simplicity I only included rodmen.

Updating is easy, remaining work is planned the same way, pouring at the 5th hour, if it rained on prior day(s) then it will still take 1 hour to pour several days of footings, in one hour you can pour a lot of concrete for footings with the same crew, no need to change plans for remaining days of footings concrete pouring.


the-same-pouring-plan-for-every-day

For slabs pouring we use separate activity, for walls and columns we plan 8 hours/day with resource loading using partial workloads.  I do not recall a single time Spider Project let me down.

Best Regards,

Rafael

Rafael,

is it true that your construction work day lasts 5 hours only, excavation crew works 2 hours, reinforcement crew works 2 hours, and pouring crew works 1 hour per day? I think that No.

If they work the way I understand and for some reason pouring was not done it does not mean that excavating and reinforcing do not proceed. Actually excavation and reinforcing may be represented as one activity with volume lag between them, pouring dependency is more complicated because it shall be continuous for portions that were selected and it depends on the weather more than other jobs. If to model this my proposal will work more correctly.

Besides, we shall not plan that the work will be done at certain time like from 10 to 11 because any delays may happen and the same job may be done from 10:15 to 11:15.

Rafael Davila
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I find it better if a single activity for this group of footings allows me to account for resource leveling instead of 18 activities.

If we have 12 buildings each divided in 2 sections each of 6 pours that makes 12x2x6 = 144 pours x 3 activities/pour = 432 activities.  If using 1 activity to represent each section we will have 12x2 = 24 activities , a reduction of 432-24 = 408 activities.

18-activities-vs-1-equivalent-activity

Variable quantities is what will make it possible to make better use of the resources that can be shared the same day with other activities.

Rafael,

we create separate activities for excavation, reinforcing and pouring.

When I wrote about analysis period it meant the upper limit with one exception - when volume of work done and remained can be easily measured.

There are many reasons for selecting detailed schedules: different resources work at different times, rain will delay pouring but permits reinforcing, reinforcement can start at one day and finish next day, but pouring cannot be interrupted, etc.

The schedule that we will use looks like below with work day start at 6:00 and finish at 14:30.

footing

With this representation in another WBS

Footing-1

By the way, performance analysis is made before each PM team meeting that here happen at least once in a week.

Rafael Davila
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Rafael,
we recommend to create activities that satisfy following requirements:

  • I do not agree and here is why.

Footings Example: Footings activity with an excavation team working on the activity the first 2 hours of the day, a reinforcing steel team working next 2 hours and a pouring team working next 1 hour. This we do frequently because of how much it rains here in the afternoon. If we start at 6 am by 11 am we should have finished with the pour.

Rain-Hours-as-usual
- they have certain units of the volume, => In my Footings example each crew have their own production rate for different volumes of work. We frequently schedule multiple teams working on different activities each team working a different work component. When there is no correlation among the different production rates fixed duration activity type might be a best fit.
- they use certain crews through activity duration, => In my Footings example the reinforcing steel resources are used on other activities during the day, same go with the other resources. Usually we want the crews to be moved to other areas instead of being idle for most of the day.
- productivity of assigned resources are the same, => In my Footings example resources work on different work components, different productivity for each work component.
- their material requirements are the same,=> In my footings example the materials requirements for the different work components are different.
- their unit costs are the same, => In my Footings example the unit cost for excavation, reinforcing steel installation and concrete pouring are different, so different they do not share the units.
- their duration is comparable with schedule analysis period. => In my Footings example the schedule is analyzed by the Client on a monthly basis, the PM looks at progress on a weekly basis and at times for critical activities on a daily basis. Frequently we update the schedule on a weekly basis plus whenever the unexpected happens and immediate corrective action is necessary plus at the end of the cutoff date as required by the client. Many of our activities start and finish on different periods, it makes no difference if it works on a single period, two or several. I am still wondering if the update period is the whim of the client or whenever it needs to be. We do not force activity duration to a maximum arbitrary duration; initially we set activity duration to whatever it needs to be, in order to be contiguous we do not split it, otherwise leveling might spread apart the activities we need to be contiguous.

Best Regards,

Rafael

Rafael,

we recommend to create activities that satisfy following requirements:

- they have certain units of the volume,

- they use certain crews through activity duration,

- productivity of assigned resources are the same,

- their material requirements are the same,

- their unit costs are the same,

- their duration is comparable with schedule analysis period.

Rafael Davila
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Vladimir,

Do you mean team modeling is of little value as using different activity for each team is equally effective?

Note I just edited my example to make it with teams working on different shifts.

Regards,
Rafael

Rafael,

we define different activities if they are performed by different crews.

Project model usually includes soft dependencies that define the order of the crews movements (from the right to the left or vice versa? or from both sides, etc.).

We also use strict dependencies but they do not work in certain cases.

If we do not want that some crew will be moved to other area before some event we use approach similar to iusing space constraints.

Rafael Davila
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Vladimir,

Some activities might have several volumes of work.  You might have CMU Masonry Walls; the activity will include CMU installation on first shift as well as tie beams and columns on second shift that must go hand in hand with the progress of the activity.  If you split the activity and link them with SS and FF logic the resource leveling can schedule them to happen at different times.

When activity includes several volumes of work how can you get the current production rates for each team?

Footings can be another example of activities that require multiple teams working on different shifts; you might have an excavation team working on the activity the first 2 hours of the day, a reinforcing steel team working next 2 hours and a pouring team working next 1 hour.  This we do frequently because of how much it rains here in the afternoon.  If we start at 6 am by 11 am we should have finished with the pour.

Rain-Hours-as-usual

Rafael,

if actual data were entered correctly it is sufficient to apply formula Actual Volume / Actual Duration shows actual production rate.

Remember that Spider Project can create reports for any period. And applying formula for the period data you will get production rate for the period.

I am not sure that understood all parameters shown in your sample reports, but it looks like all of them can be provided by Spider Proect.

Rafael Davila
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Vladimir and Bogdan,

The following image displays some of the cost & production reports we are used to.


Sample_Unit_Cost_&_Unit_Production_Report


While Project Managers will pay attention to cost & production reports the activities are managed at the jobsite by field supervisors who closely track production rates instead of costs.  Keeping track of estimate vs. per period and to-date production rates is fundamental to cost control.

I am interested on how to calculate and report production rates for current period and production rates to-date using Spider Project.

Best Regards,

Rafael

Bogdan Leonte
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Ok Vladimir,

I yield, there are some cases, like the one you mentioned where my approach cannot capture the daily costs.

But I am still not a fan of the only solution (the one you proposed) because if you have many resources that are payed by day then you complicate the model; but it is still easier than what Rafael proposed (keeping a spreadsheet in parallel with the schedule).

I understand that the schedule is only an estimation, a mathematical model, that assumes some simplifications.

Best regards,
Bogdan

Bogdan,

There is no problem with your approach if resources are paid for work hours only.

But there are problems if they are paid for work days.

Let's suppose resotce rate is 80 moneys per day or 10 per hour (if to divide as you ptoposed.

Let's consider only one day of resource work. Resource spent 1 hour on activity 1, 15 minutes on activity 2 and 2 hours on activity 3. The rest was idle time. The cost of this day calculated using hour cost is 32.5 moneys, not 80 moneys. I don't understand what did you propose for automatic correction of the hour price for each day of the project.

Besides, as the result you will get different costs of the same activities performed at different times.

Without correction project cost will be higher than the sum of activity costs. And if first use of the resource happens in the middle of the work day and ends at the beginning of the last work the resuly will be wrong.

I know that estimaring usually ignores idle time. But we hope that our users will use Spider for managing their own expenses.

Bogdan Leonte
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Vladimir,

With the risk of getting off topic idle times and costs, depending on country legislation, may be considered overhead costs. In my country idle times and costs are considered overhead costs, according to some goverment regulations, thus national norms consider only the working times of resources. But this is a little off topic, now back to our debate.

Regarding: „resource that paid daily did 5 activities in one day and besides had some idle time. What is the cost of each activity?”

Using your method you cannot determine the cost of each activity, you determine the cost of the resource, no matter the workload.

Using my method I determine the cost of the activity (number of hours x hourly rate) + idle costs (wich I consider overhead and don't neet to assign to an activity).

Resources payed daily have 3 possibilities:
1. Work every day less than the full day and get paied for the whole day;
2. Work every day the whole day, finish in the middle of the day and are no longer needed, they get paied for the whole last day;
3. Both 1+2.

Getting passed the complication of the model and multiple WBS structures (all fine with me) your method handles points 1-3 no argument there, but you cannot distribute the cost of resources to activities, unless done in a spreadsheet based or using a formula.

I don't understand on what aspect you do not agree with my suggestion. It deals with points 1 & 2, for the 3rd (1+2) the user can round activity durations to whole units (because if an activity has a calculated duration of 20,125 days it doen't matter if you round it to 20, actual data may pe 19 or 25), it captures activity costs and overhead costs.

This toppic has many aspects, for example some subcontractors want to be paied/day but work no more than 9 hours and if they work more than 9 hours they want to be paied extra, for example.

From my point of view the project model has to be 90-95% accurate, yet easy enough to create, understand, track, change; isn't this the same as you preffering to use 3 Scenarios over Monte Carol?

Bogdan,

in our discussion I suggested an example:

resource that paid daily did 5 activities in one day and besides had some idle time. What is the cost of each activity?

You suggested to transform daily cost to hour cost. Once again - what if resource worked only 5 minutes on its last work day? If you want to distribute resource cost between activities how do you suggest to distribute its idle time?

 

About the model that I suggested.

You rememer that you can create any number of WBS and some of them may be not full.

So yes, adding hammocks will complicate the model but you can create and work with WBS where these hammocks will be hidden.

Bogdan Leonte
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Daily costs are formed from working times + idle time. A resource that works 2h/day is payed for the full day. Say it costs 200 money/day; by dividing 200 to number of hours/day you get the cost/hour. If you capture idle time of reource you capture the daily cost. This of course doesn't work if activity duration isn't in whole units (2.25 days). It's not perfect but I suppose, in the end, that both solutions have pro's and con's. In the end it depends on the user. I understood your solution and will consider it for some cases, but I belive it can complicate the project model. Best regards, Bogdan

Bogdan,

you suggested to collect resource idle times on the hammock activity.

We do the same when there are different rates for work time and idle time.

But I did not understand how it helps for calculating costs of resources paid daily and activities where they were used.

Bogdan Leonte
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Vladimir,

I made a mistake when I setup the leveling on the project presented.
I forgot to set minimal quantity to zero for the resources on the hammock; now the model looks good.
I also made a correction in my initial model, forgot to setup the calendar with 1h/day to an activity.

Now let's compare the 2 solutions:

1. Your option:
a. Captures costs/day for the 2 resources
b. Has 3 hammocks
c. Has no distribution of costs assigned to activities

2. My option:

a. Captures costs/day for the 2 resources
b. Captures Idle Time and Idle Costs
c. Has 1 hammock and 3 milestones for supply+removal of resources (so 1 more activity than yours)
d. Has distribution of costs assigned to activities

See below:

https://ibb.co/khVsFHb

Does my model have any flaws? This is the question.

Kind regards,
Bogdan

Bogdan Leonte
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Vladimir,

If I understoond correctly your approach:

1. Use hammocks with 1 h/day calendar;
2. Assign costs to this hammock per hour, where the cost/hour represents the cost/day of the resource;
3. If there are multiple resources than cost/hour (cost/day) will be cost/day x no of resources. Correct?

See image below:

https://ibb.co/vz4cBXp

My problem with this approach:

1. It assumes a uniform distribution of resources, if you use variable quantity, the method will fail, unless you use multiple hammocks;
2. If resources are removed from site and then brought back, than you need hammocks for each time period;
I think it will complicate the model very much, and I think it is feasible if you have 1-2 resources for a long period of time several months.

I would like to get your oppinion on my ideea:

1. Using a hammock to capture idle time and costs, thus adding partial workloads from the activities with idle time captured by hammock you get full day cost;
2. Using milesone and resource production for the supply and removal of resources from site.

https://ibb.co/88YdPXd

Where:
(93) Removal of Labor - Bogdan - Has Resource Production - (-2) Labor - Bogdan at the end of the activity
(94) Removal of Backhoe - Bogdan - Has Resource Production - (-1) Backhoe - Bogdan at the end of the activity
(95) Supply of Backhoe - Bogdan - Has Resource Production - (+1) Backhoe - Bogdan at the end of the activity

However there seems to be a problem with this approach in the sense that resource production activities, when leveling, are delayed in order to be able to complete the hammock activity that captures idle costs.

Below is the result after resource leveling:

https://ibb.co/8D4yF2G
The expected result (edited in PDF):https://ibb.co/txMmYy3
Explanations:
Resource: Labor - Bogdan: the workload on the first 2 days is below 100%, first day 70%, second day 30%, thus the hammock should capture idel time and costs, after milestone (93) Removal of Labor - Bogdan the resource should be removed and the hammock should not display the Labor - Bogdan resource anymore;
Resource: Backhoe - Bogdan: similar to the Labor resource the first 2 days the workload is below 100%, after removal of the backhoe, hammock shouldn't capture resource idle time, after backhoe supply hammock also shouldn't capture idle time since the workload for each activity is 100% and the resource is leveled, activity 8 being delayed by activity 7.
 If this method would work properly users would be able to:
1. Use a single hamock to capture idle time and costs, thus costs/day
2. Distribute costs to activities
3. Manage resource supply/removal similar to material supply
What do you tinck, do you tinck this is a better solution? Would if be possible to make the leveling algorithm in such a way that hammocks have the lowest priority when leveling instead of resource production activities?
Best regards,Bogdan
Bogdan Leonte
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Rafael,

I don't intend to use CPM software for accounting instead of accounting software. I don't even enter materials that are below 3% of the total value of materials in the CPM model; as you said there are a lot of small materials that are used every day and it is a waste of time to keep track of them via CPM models.

Vladimir,

You are right in regard of the formulas I tested; and maybe with the whole ideea of modeling of daily costs, however I still want to try a different approach than the one you suggested and if that also fails I will yield.

Thank you for your input!

Best regards,
Bogdan

Bogdan,

it is possible to create formula that will summarise values from assignment fields but it will not solve the problem.

As I wrote earlier - if some resource did several activities in one day then it is not clear how to calculate the costs of these assignments.

For resources that are paid daily we usually create hammock activities that last from the first to the last resource usage.

Resource rate we assign to this hammock that have calendar where only first minute of work day is working. Daily rate is assigned to this minute.

Rafael Davila
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On a construction job, every day you have many cost components you must account for otherwise your cost database might be invalidated, you might have:

- Different concrete quantities for different activities, some deliveries with overtime charges.
- Some activities work only on regular time, some on regular plus overtime, other activities a combination of regular and overtime, each day a different distribution.
  Time cards for CPM data entry can be a nightmare; hours shall be distributed per cost code as well as per CPM activities.
  Time cards for Job Costing are easy; hours are distributed by cost code only.
- Equipment not used that day but based on rental per week or month.
- Margins in construction jobs is small, wrong distribution and you got it wrong.
- Job Costing Modules for Accounting Software do not get into the granularity extremes CPM Software do. When entering cost data in CPM Software you must enter the costs per cost code and activity codes while in Accounting Software you enter costs per cost codes only. This makes a huge difference in data entry.
  Imagine small purchases like nails to be used in many activities.
  Imagine you received a truckload of Gypsum Board Panels.
  In a Job Costing system usually you would do a single entry for a single cost code, in CPM software you must figure out the distribution per activity and make many entries, one for each activity you figured out the distribution.
- In CPM software when activities finish you cannot add late cost entries; by the same token you cannot add cost entries for not started activities.
- Accounting Software goes to the penny; no cost entry is ever missed.
- Job Costing gives you true total cost expenditures, unit cost to date as well as production rates.
  Unit cost makes the cost reports more meaningful.
- In order to track production rates you must enter production quantities for each cost code entry.
- CPM software only gives you an approximation to total cost because much of it is based on fictional data.

How are you planning to account for the above? A short list that in no way includes all possibilities you might encounter.

Bogdan Leonte
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Rafael, Vladimir

I agree with you regarding the partial workload of resources in the same day, in sense that my approach would result in wrong calculation and basically doubling, tripling the cost of resources at the assignment level.

This is the reason why, the field Duration [Cost/Day] would only be calculated for resources that are payed by day; in order to be able to filter them easily and find these overlaps.

The problem itself is a bit tricky, however from my experience it's better to overestimate costs than underestimate them.

The main reason for using such an approach is that I would like to be able to track actual resource hours and productivity while capturing true costs.

The problem I have in the performance archive is that after applying the formula to the performance archive the costs of resources isn't tranfered to the activity level, as shown in the table below:

Activity codeResource codeActivity nameResource nameLabor Costs [Actual]Machinery Costs [Actual]
1 Start   
3 Activity 3 1600 
3Lab_Cost_HourActivity 3Labor - Cost/Hour100 
3Lab_Cost_DayActivity 3Labor - Cost/Day1000 
4 Activity 4 700 
4Lab_Cost_HourActivity 4Labor - Cost/Hour700 
6 Activity 6  83,84
6Scafonding_Cost_DayActivity 6Scafolding - Cost/Day (24h) 400

The only solution I have to this problem is to export the table in excel and via a macro to calculate the actual cost of the activity by summing the resource costs with a loop (easily done) and then just copy-paste the results in the performance archive.

Another way I thought to do this is to create a calendar with 1 hour/work day and assign it to the resources payed by day and to track actual hours using a user field. The productivity of these resources will represent the productivity for 1 day instead of 1 hour.

Best regards,
Bogdan

Rafael Davila
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Bogdan,

The distribution of actual costs can easily become complicated for CPM software while Job Costing Modules can deal with the distributions with fewer complications. The following image can represent a common resource costing scenario.


Spider-Cost-Distributions


How you will get the distribution if using your formulas?


Best Regards,
Rafael

Bogdan,

I do not understand your proposal.

Imagine that some resource does 5 activities in one day. What is the cost of each assignment if resource is paid by days?

Rafael Davila
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Bodgan,

Usually we keep actual costs within accounting software database.  Anyway, did you executed a cost and material calculation after the second formula is applied in the Performance archive?

Good luck.

Rafael

Bogdan Leonte
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Vladimir, Rafael,

I have managed to create a procedure for calculating Costs/Day for resources that are payed by day:

Input Data:

User Fields

1. Cost per Day - Assignment value is the value of  Resource - This represents the cost/day for resources and it can be filled either in the resource table or OBS; also option Auto-fill in performance input is checked

2. Duration [Cost/Day] - Calculated by formula if (Cost_Day != '', NumDays, '') in the resource assignments table;

Formulas:

1. One for Labor Cost/Day and one for Machinery Cost/Day: c_fix_Cost_Man_Exec = if (Cost_Day != '' and  DurPlanD != '' and Type = 'Labor', Cost_Day * Dur_Cost_Day * NumPlan, c_fix_Cost_Man_Exec), where c_fix_Cost_Man_Exec is the cost component of Labor, this formula calculates the remaining cost for resources that are payed by day

2. One for Labor Cost/Day and one for Machinery Cost/Day: c_aac_Cost_Man_Exec = if (Cost_Day !='' and Type = 'Labor', Cost_Day * Dur_Cost_Day * Number, c_aac_Cost_Man_Exec), where c_aac_Cost_Man_Exec is the actual cost of Labor in the performance archive, this formula will be applied in the Performance archive after actual data input is tranfered

Procedure:

In the actual data input table I enter the number of days in the Duration [Cost/Day] [Consumed by Period] at the assignment level and the Quantity [Actual], then you Transfer the actual data input into the next version, then the second formula is applied in the Performance archive.

Howerver I have one problem with this solution: the actual costs of the resources aren't transfered at the activity level resulting in different actual costs between activity and resources that are payed/day.

Do you have a solution to my final problem?

Best regards,
Bogdan

Anoon,

I do not agree with your statement that "Schedules do not govern real construction."

In my practice project schedule creates the plans for every shift and out of sequence performance may lead to some penalties to site managers. Project schedule determines the optimal order of activity execution that shall be followed.

I join to your HAPPY CHRISTMAS TO ALL!

Anoon Iimos
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Vladimir, Yes, nothing is certain or perfect on any given situation. So you need to keep the balance as practicably as possible. Schedules are intended to keep the records regardless of conditions or actual situations. Out of sequence activities and or resources cannot be seen in real construction. Schedules do not govern real construction, but Quality Control (and Safety) governs the real timing of works (I guess most people don't realize this). And Quality Assurance ensures delivery and acceptance of real works or deliverables (again, not the Schedule). However, of course Schedule(s) is the absolute guide or map (or Headlights) for doing the works. If you go astray, then who's to blame? HAPPY CHRISTMAS TO ALL!

Anoon, I agree with your statements but out of sequience in resource constrained schedule can happen without violation of work technology.

The software may suggest certain order of work for constrained resources and for some reason this order may be violated. This is not good if the software calculated the best schedule and may lead to substantial delays.

Anoon Iimos
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Vladimir, The "Culprit" is never the "sophisticated software" nor the "out-of-sequence activities" For me, to separate "time" & "cost" is NOT planning. If this is the case, then no need for Planners or Cost Engineers. Companies shall only employ so-called schedulers and accountants. Again, the culprit is not the software nor OOS activities, but simply your Plan or Schedule in the first place. WHY? Builders or field personnel can never do "out-of-sequence" activities (OOS only exists in Schedules and never in reality). I might suggest to ban "Retained Logic" in the schedules and use only "Progress Override". Try to model your schedule exactly how you would do the works on site and you can never go wrong. This is where your "fragments library" will stand-out. Again, there are no "Short-cuts" for good Planning and Scheduling. One thing that hinders good Planning is the "absence of details", which resulted to most people doing short-cuts.

Anoon,

in my country "official receipts" can be issued only after "work acceptance".

Our planners (we do not have "schedulers") plan both schedules and budgets.

Management decisions are justified if they are profitable. So it is not right to manage schedules and costs separately. Besides it is necessary to know what expenses are expected in each month. So project model includes resources and costs.

But accounting is not based on planner's data and is always late.

Anoon Iimos
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Vladimir, Sorry, but for me, accounting work(s) is only based on "Official Receipts" (a real life fact). "Work Acceptance" is a job for QA/QC. Planned and Real Construction Costs are for Cost Engineers and or Quantity Surveyors. And of course Schedules and actual progress are for Planners and Schedulers, but most of the time doing multi-tasking, and may also cover the scope of Cost Engineers and Quantity Surveyors (that's a real life fact as well). So why the works of Planners are always wrong; and Accounting are always right? Can they not both right at the same time? (When accounting data always rely on Planners for percentage progress or actual progress)?

Anoon,

When we plan the future we take into account risks and uncertainty that do not exist in the past. For example we may allow for certain numbers of the rain days that may actually happen or not, we expect to buy materials for certain price that may actually change, etc. So our planned values are always probable but not certain. Actual data can be measured and confirmed.

Besides we estimate project status and reschedule the remaining work basing on data collected on construction sites. Accounting is usually based on the documented data and accepted works and this data are different. What is done and what is already accepted rarely coincide.

Anoon Iimos
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Vladimir, I do not agree that forward looking scheduling is very difficult or can never be done correctly (in terms of costs); While accounting processes is always accurate. Where do accounting gets the data (or who feeds them the facts) by the way? Accountants or Auditors cannot determine "Physical Progress" all by themselves. They shall always rely on data given by Cost Engineers, Planners or Schedulers. So how do most people (if not all) say that accounting data is always right or reliable? And also I don't agree with the reference linked by Rafael. I hope you understand now? :-)

Anoon,

I understood that you disagree but did not understand with what.

Anoon Iimos
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Sometimes conclusions were easily derived from wrong assumptions (very obvious from the given figures or examples). Forward looking Schedules were usually done using wrongly assumed "short-cuts", thus, always lead to out of sequence activities and or progress. While you can do an accurate "Accounting" working backwards; Why you cannot do an accurate Schedule looking forwards, when the assumptions (or estimations) and the facts should have NO difference at all? I for one do not agree (may never matter to you anyway).
Rafael Davila
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Agree, though not easy it is always good to look for practical ways to improve forward looking.

Bogdan Leonte
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I think I did not make myself clear in the post, my appologies for that.

1. I agree with you, schedule is for the future, accounting is for the past.

2. No way is it a good ideea to use schedules for accounting.

3. The issue discussed was how to create the project model in order to capture costs as close to reality as possible in order to be able to analize project cost vs project price, nothing less nothing more.

4. Actual data will be entered and corrected if needed.

5. I have read the document you posted some time ago when you posted it on another topic (thank you for that, it is most insigthful) and agree with it's content.

Hope now everything is clear.

Best regards,
Bogdan

Rafael Davila
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The way we do it accounting lets us see the past, scheduling lets us see the future.

We do not have the urge to duplicate accounting effort to see the past. Frequently accounting data becomes available after activity finishes; this alone would create hundreds out-of-sequence issues if using scheduling for accounting.  Estimating accounting data at schedule update will require future corrections when finally true data becomes available, the accounting details are so many this is not practical.

Not even for billings we use the schedule because of out-of-sequence problems.  For billings we use Excel, easier for contractor as well as client and architect for their review and approval where there are no out-of-sequence issues.  The following reference illustrates in detail what a mess if using schedule as a billing tool.

The Great Divorce: Cost Loaded Schedule Updating

By the way at home equipment rental can be by the day, by the week or by the month. If by the day only days matter for billings irrespective of hours per day, if by the weeks only weeks, if by the month only months. If returned earlier than the rental period there are adjustment rules.  If rented by the week but used more than 3 days full week rate still applies, if less than 3 days then weely rate divided by 3 is applied for each day. Each vendor might have their own rules as described in their rental agreement. How you model rental if by the month for some supplier while if by the week for other will be interesting. 

Bogdan Leonte
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Rafael,

You are right, my interest in this topic si to better and more realistically estimate future costs in order to perform an analysis between what we pay vs what we get paid for. The way you do it (wait for accounting) only let's you see the past. Also you may deal with large projects +10 mil, while I deal with small projects around 500k, for which the schedules are very short 1-3 months, for these projects the ability to model costs per day is very important because we must maximize the use of equipment.

Google translate does a pretty good job at translating the page in Russian, the image I posted is similar to the sample project in Russian.

You make a Hammock from the start of the project to the end of the project (link it to stat/finish milestone) and assign all resources for which you like to capture idle time and idle costs, then assign the maximum quantity you have at your disposal, and check the variable workload option and set the minimum workload to 0. In the Scheduling with Resource Constraints uncheck (by default it is cheked) the Minimize parallel activities and run the Resource Constrained Scheduling, the hammock will only keep idle time of the resources and quantify that idle time into costs.

Here a very basic example of optimization:

1. Resource: Digger; maximum number: 4
2. 3 Activities, each has assigned a different number of diggers

Result: 120 of idle hours if all 4 Diggers are kept on site; Total Cost: 24k

https://i.postimg.cc/zDPz9QTn/Original-Calculation.png

Optimization: By assigning 4 diggers to all activities, you will get no idle time and shorter duration

https://i.postimg.cc/661ZYY3P/Optimization-Calculation.png

With this model and the ability to calculate costs/day without waiting for accounting is very valuble for forward looking and estimatig total project costs.

Hope I was clear with this example.

Best regards,
Bogdan

Anoon Iimos
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Of course different activities have different costs assumptions; Or perhaps similar activities but of different type of materials or situations, but may use exactly the same equipment. i.e. Excavations: Soft or Normal Soil vs. Hard or Stony one. The contractor can maximize his/her profits for normal or soft excavations but not for hard excavations. Did I understand you right Rafael?
Rafael Davila
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Bodgan,

In my country machines are usually rented by the day.  The rental calculations are per day while resource usage might be less than a full day. Same resource can be shared on different activities same day, different hours on each activity and total resource usage might be less than a day. Our activities can start/finish at middle of the day and do not need to have whole day durations.  Our rental calculations are per day while our cost distribution is per hours on each activity each day, we distribute the rental according to hours used per activity each day.

My question is not about the calculation of rental per day or about at what time of day resource usage started or finished as it does not matter to rental calculations, for rental what matter is if resource was used that day, if used even if 1.25 hours hour we pay full day, the issue then is about the distribution of cost/activity.  We distribute actual as well as idle time within the activities that required the equipment.  I saw no reference in your post about resource hours distributions per day per activity for cost distribution and therefore my question.

In our country for accounting we use accounting software, for scheduling we use several scheduling software depending on what the client requires. We make the rental distributions after receiving the rental bill, preferably we use the labor time cards that distribute the hours the equipment operator worked each day on the different activities at times it is a guesstimate. For us it does not make any sense to use the scheduling software for our accounting.

My curiosity is because we use the scheduling software as a forward looking tool that can include cost estimates and their distributions. Accounting sofware will not give us such forward looking. What you are doing is of interest as a way to get better forward looking reports.  In my schedule examples dealing with cost, with a few exceptions, you will only see forward looking discussions.

  • Spider example is in Russian, I know no Russian, English a little, Spanish is my language.
  • The images are of low quality, annoying to the eye.

Best Regards,

Rafael

Bogdan Leonte
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Rafael,

At the present moment in my country there are several trends:

1. Machines are rented by the day not by the hour

2. Manpower: trade workers are paid by quantity and unskilled labour by hour or by day

3. Own resources (employes) which are paid by the hour

Thus,

When I plan and create the project model I take into consideration all of the above.

Unskilled labour which are paid by the hour/day I usually don't asign them to Multi-Resources because it is very hard to quantify their workload so I asign them to a hammock.

Regarding your curiosity, the model you presented doesn't have issues because activities have round durations (3 days, 5 days) so I can model with hourly costs.

The issue I have is with equipment which may finish the job in the middle of the day but ar payed for the whole day.

For resources that are paid hourly I can easily quantify non-productive time with a hammock to which I asign them and set it to variable workload, quantity of asigment = max number of resource, minimal workload is set to 0, then I un-check the „minimize parallel activities” in the Resource Contrained Scheduling Options.

Here is an example created by Spider Team: http://www.spiderproject.com/ru/index.php/spabout/samples/27-resource/83....

Here is a model based on your model, using hammock to calculate cost of manpower on site.

https://i.postimg.cc/cH2Y8wc5/Resources-On-Site.png

Best Regards,
Bogdan

Rafael Davila
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Out of curiosity.

  • How are you distributing costs when same digger is shared among several activities on same day? 
  • I would calculate day rental and distribute cost among activities per hours used by day on each activity.
  • The following figures are an example of quantity used per day, hours distribution and cost distribution.

Digger-Rental01

Digger-Cost-Distribution

Bogdan Leonte
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Vladimir,

Clould you also add an option for the formula similar to that "Execute Automatically In performance archive".

This would be "Execute Automatically: In Actual Data Input" and it will be as follows:

After setting the period and hitting the Ok button, then the formula would be applied to calculate the actual cost.

Also the field Number of Working Days [Actual] should be available in the Actual Data Input Table in order to avoid Modifiers.

Here is my solution with a sample

6424
cost_per_day.png

https://ibb.co/bLsQYMW

Basically to finish my solution it would be necessary to:

1. Be able to apply formulas in Actual Data Input

2. Show the actual number of resources column (which you can)

3. Show the Number of Working days [Actual], which you cannot at the moment.

Then you would apply the formula only using Actual data and you would get the actual cost/day.

Bogdan,

I like your solution.

Formulas can be applied in the performance archive but yes, activity cost shall be updated manually.

I would suggest to create special cost component for these costs. It will make the process easier.

Adding formulas in the actual input table will help. We will do it.

Bogdan Leonte
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Vladimir,

I have found a partial workaround:

1. Create a User Field called Payed by Day; which is populated with Yes and No

2. Create a User Field called Cost per Day; which is populated with the cost per day for resources which are paied by day.

3. Create a formula(s) (depending on the cost structure/resource types): Cost [Fixed] = if ( Payed By Day = 'Yes', Cost per Day * Number of Working Days [Remaining], Cost [Fixed] ); formula which is applied after scheduling

 

This is only a partial workaround due to the following:

1. Cannot apply formulas in Actual Data Input;

2. Number of Working Days [Actual] cannot be displayed in the Actual Data Input, thus manual calculation is harder;

3. In performance archive activity cost wich use resource payed by day needs to be ajusted manually.

For this solution to be a little easier to use I think that allowing formulas in the Actual Data Input might be the easiest way, or  at least allowing to show the Number of Working Days [Actual] in the Actual Data Input so that manual computations may be done with more ease.

What do you think?

Best regards,
Bogdan

Bogdan Leonte
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You are right, and I have this situation, for which your solution si real good; however I also deal with short projects (1-3 months) which are fast passed and use several machines during several time periods, if I were to create hammocks it would be quite a task to set up the hammocks.

And from experience in a 1 year project a couple of days don't count that much, but for a project that is for 1 month a couple of days is a lot, both in time and in cost.

In our projects heavy equipment is usually leased for long time and usually once.

Bogdan Leonte
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I will use the method you described, with hammocks.

The only solution I have to your solution is to create a macros in excel (use the export to CSV then import) which will create hammocks for resources if the time gap between their usage is less than X days (specified by the user) but I don't think it will prove very productive.

 

Thank you for the solution.

Not easy. We will think about your proposal.

The way I suggested is reliable and not too hard. Hammocks may be hided or put in the separate phase.

Bogdan Leonte
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Understood,

however this method may complicate model a lot if you have 10-20 contruction machines which have this type of cost. Couldn't there be an option for assigments "Round to full day" wich will round the costs to a full day according to the resource calendar, this way you will be able to take into costs for days in which the resource cannot work a full day due to weather conditions, for example.

Also what happens if you use the resource from day 1 to 5, then the resource leaves and comes back on day 60 and works from days 60 to 75.

We use hammock activity that starts with the first usage of backhoe and finishes with the last.

This hammock has special calendar with one hour per day work time. This one hour finishes at the first minute of backhoe work day. The cost of using backhoe is assigned to this hammock as the cost of backhoe day per hour.

The cost may be assigned directly or as dummy resource backhoe cost.