Through bolting a concrete topped metal deck.

[StrEng007]

Anybody ever through bolted a base plate (top side) through a composite metal deck (metal deck with concrete topping)? I've used Hilti's Profis for concrete over metal deck and cannot get the breakout to work for tension. I'm confident with two base plates (top of slab, bottom of deck) with bolts, the tension is a non issue as it bypasses the concrete.

 

[RenHen]

I do this pretty regularly when I don't have sufficient breakout capacity in the concrete. Got any questions in particular about those sorts of connections?

 

[StrEng007]

Do you make your plates large enough to guarantee engagement of a certain number of flutes, or do you investigate all field locations?

Also, if there is a shear component to this, do you worry about any eccentricity or double curvature of the bolts, especially for those anchors that are unsupported?

 

[RenHen]

How I detail it depends on the information I have, if I don't know where I'm landing relative to the flutes, I size the plate to span 3 flutes, that way if it gets shifted around it'll always hit at least 2. If I know where I'm landing within a tolerance, I'll detail the plate to grab 2 flutes & overhang on either side by the tolerance amount. I'd prefer to detail it to grab 1 flute or land between flutes so that I don't have to assume the plate spans & bends between the flutes, but I rarely have good enough information to confidently size the plates for that, occassionally it works out for one off field conditions.

I avoid this for conditions with shear or try to provide something else to take the shear out. If it's being loaded from the top, I would think that shear would primarily be transferred into the concrete on the top and take a small amount of bending allowed by concrete crushing, the hole size, etc. but it doesn't feel like a good shear detail to me so I haven't dug into trying to quantify or justify that so far. If it's being loaded from the underside I'd be very concerned about shear. Last time I had one with shear on the top, I bolted a tube between the top plate & concrete, and added angles to the side of the tube that were anchored into the concrete. Not an especially elegant detail but it worked.