Where's the Diaphragm Chord?

[steellion]

I have a 160'x160', one-story warehouse bay with shear walls on the perimeter on 3 sides (the 4th side is a building expansion joint). The roof is an untopped steel deck. I have been able to check that the diaphragm meets acceptable deflection limits in the direction of one shear wall. My question is when the wind is blowing in the direction of the 2 walls, what is acting as the chord member of the diaphragm? And what force do I design the chord for? Typically, I would design the chord force for M/d, where d is the distance between extreme lateral elements, but there is only one lateral element in this case.

 

[BAretired]

Hmmm...after thinking about hokie's comment, I don't think I calculated the wind moment correctly. The shear center should be outside the building if we look at the three walls as a vertical channel.

That means the eccentricity of the c.g. of wind force to the shear center is greater than 80'. Hmmm...need to think on that for a while.

It doesn't seem like a good idea to leave this structure open on one side.

BA