# How should a bridge deck closure pour be positioned?

The Question:

Where should a closure pour be located relative to centerline of girder and how should the closure pour width be detailed/designed?

And now, a little background:

When designing a steel girder bridge using phased construction with dead load deflections exceeding 2", my state (Nebraska, USA) requires a closure pour. No guidance is provided on how to locate or design the closure pour. As a point of reference, I'm dealing with a 100 ft span and a 44" deep girder.

I've done moderately extensive Googling and found varied suggestions. Align the edge of the pour with centerline of girder. Don't align the edge of pour with centerline of girder. 2' minimum width. 3' minimum width. And an interesting suggestion from Nevada DOT (p. 16-10) that:

The required width can be estimated by considering the closure pour to be a fixed-fixed beam and by limiting the stresses in the concrete to the cracking stress.

Which sounds quite promising, though I haven't fully digested the particulars of execution.

Where my noggin really starts to hurt is when I start thinking about how my girder deflections will be affected by phasing and a closure pour. Say my girder has a tributary deck width of 96" in the finished condition. But during phased construction, only the left 2/3 of this deck will be poured. Do people execute a series of analysis runs looking at all the intermediate conditions and the progressive deflections/stresses?

Thinking about where to put the pour, however, I'd wager a good position is around one fifth of the total span between the "Phase 1" and "Phase 2" beams. I come to this considering that slab as a fixed-fixed beam (which implies I'm considering the slab to be one-way). Such a beam has, under uniform load, zero bending moment approximately one-fifth of the span away from the supports (more precisely, $\dfrac{1}{6}\left(3-\sqrt{3}\right) \approx 21.13 \%$). This should reduce the stress directly over this spot.