Support settlement-slab deflection

[Matt_Struc]

Hi,

I am designing my first building over two-storey height including sizing slabs for longterm deflection. I read in the design codes that the support settlements and formwork settlements should be accounted for when considering refined defelection calculations.
This points is very unfamiliar to me. I usually use csi SAFE to run longterm cracked analysis.
My question is how do other practicing engineers handle this clause or is there any simplified methods as it seems to hectic to consider this effect.
Thanks!

 

[dik]

Is there a geotekkie on the project? There should be... Can you provide him with a foundation plan with loads applied. He should be able to give you a design criteria to minimise settlement and also provide you with a magnitude of settlement.

Dik

 

[WARose]

I read in the design codes that the support settlements and formwork settlements should be accounted for when considering refined defelection calculations.

Long-term support/foundation settlement I think about sometimes (especially when I ID a potential problem). It's kind of hard to say (though) what will settle and how much it will. The number of possibilities are endless. You just have to use your best judgment.

When you say "formwork settlements", are you referring to formwork deflection? Because (for example) a footing cast on the ground obviously shouldn't have such a issue. There will be some initial settlement from the placement of the concrete.....but not because of formwork.

 

[Matt_Struc]

Thanks for your responds!
What I meant by formwork settlement is what we have when we pour a fresh slab on formwork that is in turn supported on a susbended slab that again is supported on formwork supported on a suspended slab. Ultimatly this would create some kind of cumulative defelction as the first suspended slab carrying all the formwork above it defelcts which leads to the slab of interest deflecting as a result