Composite Column Shear Studs 1

[EngrRC]

Does anyone have a reference that explains in detail how the shear studs of a composite column are designed and where they need to be provided? In particular, I have this confusion:

For a multi-level composite column subject to compression load only (for simplicity), do the shear studs have to be provided within a certain distance from EVERY slab level based on the cumulative compression force at that level? I have seen designs using the peak axial force and provide shear studs at multiple levels based on this.

Or do they only need to be designed at the top/bottom level where you have the transition between composite and non-composite sections (using the cumulative compression force), and for the intermediate levels the shear studs will just be based on the incremental loads per floor?

 

[icebloom]

Theoretically composite columns can develop full capacity as long as there is enough bond strength between the steel and concrete component (for which there are equations in various standards). If at any location the bond strength is insufficient eg due to load introduction at floor level, then shear connectors should be detailed to introduce the full load.

Good practice would be to detail shear studs at each level equivalent to the amount of load introduced.

Shear stud capacity for load introduction is usually calculated the same way as you would if it was a stud in a composite slab (i.e. lesser of the concrete capacity or steel capacity - pretty sure most standards around the world use the same equation). The Eurocode (EN1994-1-1, which can be easily found for free on the internet) has a section discussing load introduction (6.7.4) which is quite good.

The paper "Load introduction to composite columns revisited - Significance of force allocation and shear connection stiffness" by Grzeszykowski et al can also be found on Science Direct for free and discusses these topics.

 

[EngrRC]

Thanks for the response Icebloom. Your explanation matches with my understanding - that the shear studs only need to be designed for the transferred force at that level, and the axial force from the composite column above shall not be considered in the stud design.
Just that I do not see enough illustrations from codes (AISC/Eurocode) about the latter point, and most engineers insist on including this axial force.