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Composite Negative Moment

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OzEng80

Structural
Jan 8, 2006
147
Hi

What is the approach for composite design for a double span steel beam with a concrete slab (precast decking with topping) over? I have found ample references to simply supported beams but nothing for continuous slabs.

My scenario is basically:
A 12m beam supported midspan with a 6m tributary width of a 200 thick slab and 5kPa live load. I am getting a 460UB without any composite action & this seems too big…

Should I treat the beam as fully restrained and ignore composite action (this is how I got the 460UB)?
- What is the minimum number of studs to put in?
- Wouldn’t anything less than providing studs for ‘full’ composite action shear them off?

Should I design the beam using existing methods between the points of contraflexure and use just the steel beam for the negative moment?
- Continuing the stud size & spacing over the internal support would result in tension being applied into the slab. Should I discontinue the studs (& even bondbreak) over the internal support to allow slippage across the interface and prevent tension in the slab? Do I need to check rotation or something?

Should I design the beam using existing methods between the points of contraflexure and use a composite section for the negative moment?
- I could do an equivalent section using the reinforcing in the slab only?

Thanks for your assistance!




 
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I dont think you will find anything in the australian codes.

British codes and eurocodes cover it well though.
 
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