Composite Metal Deck

[XR250]

When checking deflection in a shored composite slab (after shoring is removed), Do I use “Id” and E for steel or E for concrete? (I assume E-steel as the numbers don’t seem to make sense otherwise). For long-term deflection, multiply DL deflection x 3?
Also, this is going on an exterior terrace with flagstone on top. It is a 3-span condition. The arch. is very concerned about cracking. We are around L/d = 25 and will check vibration. I was thinking to add negative reinforcement over the beams as required. However, what about putting a caulked joint in the slab and flagstone over each beam to keep the areas smaller? We could also do 2 pours to get the same effect. It will have a roof but no walls. Money is not really an issue here.

 

[TRAK.Structural]

I've done top bars over girders a lot in commercial type buildings, but not over the beams.

For construction joints, what I've seen is the joint placed at 1/3 points when perpendicular to the beams, or centered between beams when the joint is parallel to the beams. In either case, usually some #3 bars x 36" long centered through the joint

 

[jhnblgr]

I have not looked this over much but might be useful https://wirereinforcementinstitute....3277/2858/2021-06-07_EXAMPLE_CALCULATIONS.pdf

 

[jhnblgr]

https://www.steelconstruction.info/images/b/b8/SCI_P300.pdf

https://ascsd.com/files/FloorDeck.pdf

 

[haynewp]

If the Id is including the hardened concrete then I would use the E for concrete and not the E for steel. I assume the Ic stands for cracked which is going into the Id equation you posted.

 

[PMR06]

If that table is from a vendor calculating per SDI (looks like Vulcraft so yes), then Ic, Iu and Id are moments of inertia transformed to steel.

 

[haynewp]

Agree, use E steel if it states transformed.

 

[XR250]

Agree, use E steel if it states transformed.

Yup, just did the math on it and it is def. E-steel. Was getting huge deflections otherwise.
Looks like my long term deflection is 7/16" for a 14'-3" simple span. I think adding the top bars and forgoing the joint is better to help mitigate long term deflection.
Thanks y'all.