Composite Floors - Construction Joint Location for Girders

[marinaman]

I have a composite floor where the general contractor wants input from me regarding where he can place construction joints. The elevated slab is too big to be poured in one day.

The beams are roughly 8'-0" o.c. The girders span 32'. The beams span 42'. The deck is 3 1/4" lightweight over 2" metal deck (5 1/4" total thickness).

Since the beams are 8'-0" o.c. I am going to allow him to place a construction joint at the deck midspan between beams.

The question I have is, what is the best place to locate the joint as it crosses over the girders (perpendicular to the girder), or does it matter? I thought about 12' from either end of the girder.....and I thought about 4' from either end of the girder. The GC would prefer 4' from the end of a girder....but I worry about it being right there because of the horizontal shear transferred between the composite deck and the top of the girder via the shear studs, near the end of the girder. Does a joint, perpendicular to a girder span, have any impact on the girder capacity depending upon where along the girder the joint crosses?

Honestly, I'd like for the joint to be 4' from the end too, but I can not find any written data that this would be an acceptable location.

Any input on construction joint locations that run perpendicular to girders? I would appreciate it.

 

[dik]

Can you put joints at the ends of the beams and the girders... that's where the rotation will occur.

Dik

 

[marinaman]

Howdy Dik - I need to consider the composite flange location of the beams, and, the location of max shear in the composite deck, and with that in mind, I am locating the joint in the composite deck at the mid-span of the deck, between beams.

Girder wise, I'm wondering if the joint location matters or not. The joint will be perpendicular to the girders. That said, it appears to have no effect on the composite flange width. Seems like the only consideration is whether or not its ok to place the joint within the last 1/3rd of the girder span or not.

 

[dik]

I've often run dual lines of headed studs with a tooled joint between them. Girder flange has to be wide enough.

Dik

 

[jayrod12]

Do you need the composite capacity for shear? generally speaking in my experience the shear capacity of the steel member alone is more than adequate.

 

[dik]

he may need the flexural capacity at mid span...

Dik

 

[hokie66]

Judgment call, but midspan between beams and 4' from ends of girders sounds good to me.