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Concrete Frame

14 replies [Last post]
Konesh Sridaran
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Please help me on this traditional concrete frame cycle time :
2 core walls, 12 cols and 18m x 12m slab

is 3 weeks from verts start to slab finish sound about right?

Many thanks

Daran

Replies

Mike Testro
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Posts: 4409
Hi Balaram

Send me an email to planning.services@xlninternet.co.uk

I will post it off.

Best reagrds

Mike Testro
Balaram Joshi
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Hi Mike,
"I have demonstrated in PP how a proper detailed bottom up programme can be put together for an 8 storey insitu concrete structure in just 20 minutes."

Can you post once again your programming method as mention above. Or you can send me in the following mail address:
joshibalaram@yahoo.co.nz

Regards
Balaram
Konesh Sridaran
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Rafael/Mike,

Thanks very useful information.
Mike Testro
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Hi Rafael.

Better let Carmen explain the difference between left hand and right hand balls.

I once owned a left hand drive motorbike - work that out.

Best regards

Mike Testro
Rafael Davila
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Mike

I never questioned the validity of your method, but my clients natural planning is by using “lags” and follow good practice by keeping a good level of detail using 20 days for our maximum construction activity duration and avoiding any lag above 10 days. In this way we can measure progress and keep our schedules at the same time valid and simple, not killing the purpose of the tool by going into unecessary details.

The above duration limits seems like the consensus in USA practice, common in our CPM specs, from my experience in a US territory. The schedule scale is therefore relevant to keep a 50% minimum overlap.

I preach options; in my world, neither yours nor my Contractors ways are prohibited. Blame it to the fact that I am a left handed person, I will never force others to write left-handed.

Look at the size of the building, seems like a single slab pour per floor. For shoring and re-shoring theory the following link can be a good start.

http://www.concrete.org/General/CI2802Stivaros.pdf

Best regards,
Rafael

No wonder, now I know who at the bowling alley hides the left handed balls.
Rafael Davila
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Kon,

I hope you have enjoyed our last postings, a bit of fun at times is good. I am not sure if you noticed I edited my posting no 8 to include a reference on re-shoring but I would like to call it to your attention.

You have two required timings: one for vertical shore removal and to re-shore immediately, and then you have a second timing required to remove vertical re-shoring a few floors below.

The first one, vertical shore removal, is usually required either by a minimum required strength, at times a combination strength and time to account for deformations in addition to strength. The required strength will be a function of design load ratios, span and geometry of the slab. This is usually specified by the contract documents.

The second, removal of re-shores is usually lagging a couple of floors below your shore level, these you cannot remove merely by the lower slab having the required strength but also must consider the required levels of re-shoring until the next cycle replaces the re-shoring level to be removed. The shoring and re-shoring plan in multistory buildings is usually to be submitted by the contractor and evaluated by the structural designer. Because usually a contractor have done this many times for the type of structure before, he will know the required cycle even before submitting the plan.

At home we usually have one level of shoring and two levels of re-shoring for flat slabs while an additional level of re-shoring is used for concrete joist construction, essentially a matter of design dead load and live load ratio.

At condo buildings if the ceiling is to be exposed and cement plastered we usually schedule cement plaster ceilings before concrete blocks installation.

Once you know the concrete pour cycle, removal of re-shoring will follow the cycle but at a few floors below.

My intention with the reference is for you to have a conceptual understanding of the sequence and why. It might sound complicated, we have to leave it to the Project Manager, scheduling will follow with ease.

Best regards,
Rafael

Rafael Davila
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Ok I got it, you only know Candlepin Bowling, I thought it was only a New England thing, not the Old England. This is a game for the ladies.
Mike Testro
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Hi Rafael

I cannot think of any American ball game that did not originate in England.

Even baketball is based on netball.

Best regards

Mike Testro
Mike Testro
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Hi Rafael

Your use of two activities - vertical overlapping horizontal - presumably for each storey level - is two broad to be accurate.

You need to place the position of the end of 1st curing so that you can strike the slab forms so that under slab M&E can start and the forms re-used - this determines the number of sets of forms and re-use.

Then you need to know the end of the 28 day curing so that you can pinpoint removal of props so that block walls can start.

I have demonstrated in PP how a proper detailed bottom up programme can be put together for an 8 storey insitu concrete structure in just 20 minutes.

I use your method of resource allocation from the estimate / cost plan using just one resource that I call "hours".

In some circumstances the cost plan is broken down into Lab - Plant - Mats - O’head in which case you do not need to apply percentages which are generally guesswork.

Best regards

Mike Testro
Rafael Davila
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Kon,

We usually use two activities to schedule the typical floors concrete schedule, one activity for vertical elements (walls and columns) and another activity for horizontal (elevated slab and beams) somewhat overlapped, cycle duration usually is governed by type of slab (flat slabs, beams and slabs, concrete joist slabs) that is assuming you have enough forms. On average for flat slabs the cycle is one to two weeks, for beams and slabs two to three weeks and for concrete joist slabs the cycle is four weeks on average. These assuming that for the start of the first cycle all forms are prefabricated. We believe for scheduling purposes too much of a detail kills the purpose of the schedule to be used as an effective management tool. Of course the details are taken into consideration to determine and sharpen the appropriate durations for our level of detail.

For labor intensive activities one method I use for our initial activity duration estimate is to determine the labor cost for the activity in question from the job estimate. Because these estimates are usually detailed as per Samer Breakdown (seems like a universal agreement on to the level of detail for estimating purposes) we consolidate these estimates into our activity level of detail for scheduling purposes. Sometimes cost estimates give you a grand total so you will have to apportion the appropriate amount to the activity.

Then we estimate a reasonable crew size and our crew cost/day from average labor rates. You got to ask the estimator what costs are included under his labor cost estimates because some estimators include all employers’ payroll contribution as part of the direct labor costs while others do not. This is crucial as to be consistent with your average labor rates. On average our employers’ contribution ratio is a 32% of direct labor cost.

The activity duration will follow from the basic cost formulas:
total cost = cost/day x days
days = (total cost) / (cost/day)

We add a 15% to this time estimate to account for the fact that not always crew composition will be at full.

The initial estimate is usually based on a reasonable crew size. For activities that fall on the critical path some adjustments will have to be done after you have created the initial schedule with all activities and logic, in order to get your schedule to match total contract time.

At times the only thing you have on hand is an architect best estimate; you will not have the breakdown itemized by labor, equipment, materials, subcontracts and other, just a single figure that includes all. In such case you can go to a ratio of labor to total cost. We reduce total estimate by 15% to get out the overhead and markup costs out, if spread under these items, then an average percentage of 40% is applied to get an approximation of direct labor costs including employer’s contribution.

We are planners and schedulers, the basic concepts of estimating are enough for our scheduling needs, is the estimator who is concerned about precision, all we need is to know how to interpret his estimate.

Beware that not always labor is the driver to activity duration but in occasions equipment is the driver.

I ask my excuses to Kon and those who are experienced on the cost estimating issue, I just felt that at times it is good to share our methods.

Best regards,
Rafael
Samer Zawaydeh
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Dear Mike,

I agree with you because the title of the thread is Concrete Frame and that would automatically indicate that the span is large. Hence, we need longer than 21 days for curing.

With kind regards,

Samer
Mike Testro
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Hi Samer

Slab curing is normally in two stages - 3 days for removal of forms + 25 days for removal of props.

Also curing should be on a 24/7 calendar.

Best regards

Mike Testro
Samer Zawaydeh
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Dear Kon,

It depends on the material and manpower that you have to complete the job. Assuming that you have all that you need to complete one floor per cycle, the activities would be as follows:

I. Vertical Elements
1. Reinforcement of Columns (2-3 days)
2. Shuttering of Columns (1-2 days)
3. Concreting Columns.
4. Deshuttering Columns. (1 day)
5. Reinforcement of Core Walls (3-4 days)
6. Shuttering of Core Walls (1-2 days)
7. Concreting of Core Walls
8. Deshuttering of Core Walls.
II Horizantal Element

9. Slab shuttering (3-5 days)
10. Reinforcement in Slab (4-6 days)
11. Electromechanical in Slab (1 day)
12. Final Leveling and support check.
13. Concreting.
14. Curing.
15. Deshuttering of slab as per span requirements.

I hope that you benefit from the information. If you have a more specific need, please let us know.

With kind regards,

Samer
Mike Testro
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Hi Kon

Wait for a while and Samer will be with you.

Meanwhile email me at planning.services@xlninternet.co.uk and I will send you an adobe method for a concrete structure up to 8 storeys.

Best regards

Mike Testro.