Purpose of non-structural topping over PC planks 2

[WWTEng]

I have a proposed floor with 10" pre-cast floor planks topped with 2" non-str conc topping. The arch asked if we could get rid of the topping and she can use a wood flooring instead as a finish. My response was that the 2" is nominal and it varies a bit across the span of the plank and is basically there to provide a leveled floor. Was I right? I always thought of this topping as a tool to provide a level floor in a plank that has camber/deflection.

 

[ron9876]

It is a composite system. Check your load tables and you will see that a plain 10" plank won't carry as much as 10" + 2".

 

[WWTEng]

ron, the topping is non-bonded non-structural.

 

[JedClampett]

You are correct for that and other reasons. The hollowcore has gaps (which are grout filled) which are likely to be uneven. The hollowcore itself has a very rough finish that the wood floor might not adhere to. It adds strength. And finally:
WHY DOES YOUR ARCHITECT CARE?

 

[JAE]

Typically 2" toppings are structural. The tops of hollow core planks are roughened and the bonded topping serves to increase load capacity, level the floor and also to provide a better diaphragm behavior.

Without the topping there will be irregular joints and a curved (cambered) floor level. Also, the topping is used as a cap and means of connecting the plank system to supporting walls.
Without the topping, the connection between wall and plank is more difficult.

 

[connect2]

Seems to me that a minimum of 2" bonded topping constitutes a rigid diaphragm floor, otherwise it's not a rigid diaphragm unless suitable mechanical connections between panels are provided.

 

[WWTEng]

Thanks all.

Jed...the architect believes that taking out this topping will save money. She is unwilling to re-think about the arched (actually semi-circular) doors on both entrances and some other rather lavish features but removing topping is supposed to make up for that.

 

[ukengineer58]

Not sure about some comments. Non structural is non structural but it does provide a level floor as the Planks are cambered and also serves to disperse point loads so not to overload the holes in the planks. In uk they can be tied together

 

[ukengineer58]

But I will say your architect sounds like an idiot

 

[hokie66]

Non-structural topping is just for leveling. I don't know what type wood flooring the architect is proposing, but if it is just a floating floor, the untopped planks will not provide an acceptable substrate.

 

[msquared48]

Sorry... I didn't see the little, non-important noting of the topping as being non-structural in the subject line.

I have cleaned my glasses.



Mike McCann
MMC Engineering

http://mmcengineering.tripod.com