Flexible Moment Connections (Type 2 Wind Connections)

[WCEngineer2]

I am looking at using Flexible Moment Connections for the lateral system of a (2) story building with perimeter ribbon windows and light gauge metal stud exterior walls with a brick veneer. I've done research on these connections and found they have been used successfully used on buildings up to (7) stories in height, including the Empire State Building. However, when I run my frame I am having difficulties limiting the drift due to wind, to less than H/500, using the 10 year wind load calculated per ASCE 7-05. The column grid is regular with (3) bays at 28'-0" in one direction and (5) at 24'-0" in the other. The floor to floor heights are 14'-0". I've modeled the frames with pinned bases, and only the windward connections are rigid while the leeward connections are pinned to account for the shakedown theory. The girders are modeled as W24x55's framing into the column web, and the beams are W16x31's framing into the column flange. Even with W10x54 columns, I am still having difficulties with the drift. To me the beam and girder sizes are reasonable, but I have a feeling I will get push back on the column sizes. At this point I'm scratching my head and trying to figure out how it would even be possible to get a building higher than (2) stories to work these type of connections, without significantly over-sized beams, girders and columns. Can anyone provide advice on what I can do to better my situation? Thanks.

 

[bookowski]

Detailing your base to get fixity should improve the drift quite a bit - but it may or may not be worth it.

I don't know if people still use those connections even though they are described still by AISC. Most of the early steel buildings (at least in my area) used this type of connection and even though it has worked fine you can't really get the numbers to work out. Those early buildings still had very heavy masonry walls which most likely are a major contributor to stiffness.