Most cost efficient column layout in RC buildings

[ramihabchi]

hi,
In general,what is the most cost efficient column spacing for a flat slabs structure?
also,I have found on the internet a research done for framed structure saying that for narrow slabs(example 30m x12m )dividing the slab in one way panels (15mX6m) leads to more economical design than dividing it into 2way panels(5mX6m).I want to know if this would be true for narrow slab of size greater than 30mX12m for example 60mX24m.
And is it true also for flat slab?

 

[dik]

I'd probably go for 6m x 7.5m with a 150 or 180 slab and maybe 150 or 180 drops... but something of that ilk...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik

 

[r13]

Maximize the floor area tribute to the column, and minimize the slab thickness required for strength and serviceability.

 

[hetgen]

There are many factors to consider. viz loading, the number of spans, prestress or reinforced, etc...

Check this from CCA A, the clip below is from pg. 18

 

[Retrograde]

One way to approach this is to figure out what the minimum slab thickness required for fire rating is, and then choose a column layout to suit that thickness.

 

[Complete_Columns]

Agree with Hetgen that there are a lot of different factors that could influence the most efficient layout.

Would you be able to provide a link to the research?

Complete Columns

https://www.completecolumns.com/

 

[ramihabchi]

thank you for the answers.
In the link below you can find the mentioned paper.

https://www.researchgate.net/public...ng_Frame--A_Typical_Computer_Aided_Case_Study

 

[captain_slow]

Many ways of looking at it but ultimately the cheapest concrete structure is probably one with a symmetric arrangement of shear walls and some sort of a 2-way flat plate on columns type of thing. Remember that unless you have actual line supports for the one-way slab (such as continuous walls) any one-way system with band beams is still a 2-way slab, it's just that a decision is made to simplify the loadpath, which aids with documentation. I never made a case study of it, but I suspect that one-way and two-way systems will probably come out to almost the same cost material-wise. Any difference in cost is probably negligible and will be less than the spare rebar that builders will end up burying within the slab.

It is important to bear in mind that formwork is a considerable cost in concrete construction. Generally speaking, banded one-way systems can be cheaper to build if one utilises sacrificial formwork for the slab panels (stuff like profiled metal decking) - in this case cost of formwork is decreased because sacrificial formwork is easier and quicker to erect thus decreasing the amount of required temporary formwork. That is why banded systems are quite popular nowadays. Having said that I have recently had feedback on some of my projects where construction management have expressed preference for flat plates.

In the end the most efficient structure is the one without transfer levels.