Hollowcore Diaphragm Deflection 1

[Baffled Engineer]

Hello. I'm looking for a design guide on how to calculate hollowcore diaphragm defleciton assuming it is flexible and simply supported. I can't seem to find any guide in the PCI manual about this topic.

Thank you.

 

[BAretired]

Calculate the simple span deflection using recognized princicples.

BA

 

[KootK]

You might google the works of SK Ghosh and Wayne Kassian as both have done a lot of work in this space. Baring a good find there, in many cases, I'd treat this as one might a fully cracked, CIP slab. What elements will serve as the tension chords in your setup? That can be tricky for slabs without toppings which I assume to be the case here.

 

[Baffled Engineer]

You might google the works of SK Ghosh and Wayne Kassian as both have done a lot of work in this space. Baring a good find there, in many cases, I'd treat this as one might a fully cracked, CIP slab. What elements will serve as the tension chords in your setup? That can be tricky for slabs without toppings which I assume to be the case here.

Thanks. I will look into those works. There is no topping layer. The chords are precast girders on two sides of the building and 30M bars cast inside the hollowcore along the other two sides. I'm not sure where to get the shear stiffness of grouted key joints...maybe they are in those references you provided I'll have to look at them.

 

[KootK]

This documents contains some shear stiffness estimates: Link

I expect that your deflection will be dominated by your chords and the shear connections to them:

1) The 30M bars elongating in the one direction:

2) Potential, cross column connection slip in the direction where the girders are the chords. If your diaphragm to chord connections will be welded embeds, then that should be pretty stiff. If it will be drilled dowels, as is usually the case in my work that will have some give to it in a way that I don't currently know how to quantify.

 

[KootK]

This probably doesn't need to be said but I sure do love me a structural topping when diaphragm demands are high and/or seismic. I've never relished the grouted keyways for in plane shear transfer. Those are betted suited to vertical shear transfer in my opinion.