Precast Plank - Structural Topping vs Non-Structural Topping 3

[RFreund]

What is the difference between Structural Topping vs Non-Structural Topping in terms of specifications required or performance requirements?

I understand that structural topping is considered to act compositely with the planks but what is done differently when a structural topping is used vs a non-structural topping. Assuming they are both concrete?




EIT

 

[ishvaaag]

By using the Ctrl-F trick or search of incidences in PCI 6th handbook one can find the main incidences soon such:

Do not relay in FRP for mechanical reinforcement in toppigs.
Be aware that the tables for topping use fc=3 ksi in the topping.
Other superior strengths can be used, as seen in the examples.
When no topping ties must be provided to ensure integrity and diaphragm action.
That ACI uses to exclude non-topped structures when diaphragm action is considered (except equivalent performance is met by other design).
Since ACI 318-02 one should repeat the search in 318-08 for the incidences.

Other than that and for composite action all is to follow science of construction, considering what available at the moment. Non composite toppings should normally considered only as weights.

 

[ztengguy]

I think Ishvaag hit it right on the head of the nail. Nothing to add here.

 

[RFreund]

Thanks Ishvaaag.

I will look through the PCI handbook as I beleive we have a copy (should have thought of this first).

As far as practicality goes - Is specifying a 2" structural topping with WWF reasonable? It seems like in this area, Illinois, most toppings are nonstructural so I want to make sure that I convey this to the contractor.

EIT

 

[ishvaaag]

The issue is more or less addressed here.

http://www.eng-tips.com/viewthread.cfm?qid=182794

I think most here (Spain) wouldn't blink on using a thin wire mesh to reinforce such topping, bout of course everyone has its advocates.

 

[UcfSE]

Nonstructural topping is usually gyp-crete or some other self-leveling compound. You'll need to make sure you evaluate compressive strength of the self-leveling topping so you get a good product with its intended use, eg is it a wearing surface also, what thicknesses can it be applied in. With nonstructural, you'll need to check the stress in the keyways between the plank in order to develop a diaphragm, limiting it to 80 psi factored.

 

[RFreund]

Thanks guys. I also found a couple good references from spancrete's span notes and research:

http://www.spancrete-sma.com/pdfs/ResearchNotes/1011.pdf

http://www.spancrete-sma.com/pdfs/spanNotes/spanNotes11.pdf

http://www.spancrete-sma.com/pdfs/spanNotes/spanNotes11B.pdf

EIT

 

[UcfSE]

This is also available for free, if you haven't seen it yet.

PCI Hollow Core Slab Design Manual