# Slab



## Engineer22 (Feb 10, 2018)

spacing?


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## MA_PE (Feb 10, 2018)

Depends on the design criteria.  AASHTO has minimum deck thicknesses based on span.  Any of your criteria may control thickness.  First thing to check would be the code basis for design if they have a provision for minimum thickness.


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## SE_FL (Feb 11, 2018)

If you have this question on the exam you may be given a starting point. Otherwise you will have to assume a thickness to evaluate the dead load for the shear and moment calcs. But generally, I have seen heavy loads are controlled by shear and longer spans are controlled by moment, but not always the case. During the exam you will most likely need to check all parameters unless the question provides a clue.


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## sayed (Feb 12, 2018)

there are design provisions on ACI

either that or theoretical plate analyses, which would be extra tough being that reinforced concrete is a composite system


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## OHBridgeGuy (Feb 24, 2018)

Engineer22 said:


> If you have a one way concrete slab, is the thickness sized by bending moment, deflection, loading duration, or rebar spacing?


Don't forget shear - that can often control slabs and footings.  I usually start with minimums (by span, ACI, AASHTO) then check shear, then moment - both for ultimate strength and minimum moment, then rebar spacing (crack control), then any other provisions.  This order usually reduces any rework due to a later check failing and making me iterate.


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## Engineer22 (Feb 24, 2018)

Is it usually determined by one of those factors primarily, or first? What is checked first?


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## PowerStroke79_PE (Feb 27, 2018)

Engineer22 said:


> Is it usually determined by one of those factors primarily, or first? What is checked first?


I always check code first. After that I move on to shear and moment capacity. Either way, you have to check everything.


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## Engineer22 (Mar 2, 2018)

Hemi79 said:


> I always check code first. After that I move on to shear and moment capacity. Either way, you have to check everything.


I understand. Thanks so much to you, and everyone in this helpful forum!


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