Steel deck diaphragm with all braces at interior

[SocklessJ]

- Single story building, 150'x200'
- Vertical system: Steel roof deck, bar joists, wide-flange girders, HSS Columns
- Lateral system: steel roof deck diaphragm, vertical braced frames (R=3)

With windows across the front wall, I planned to shift that line of bracing back a bay to avoid a 3-sided diaphragm. The architect then asked if I could move all bracing to interior walls to allow for horizontal expansion.

I tried this in ETABS using a semi-rigid diaphragm and drifts are low. Is there any reason not to go this route? Other than requiring more coordination every time they mess with those interior walls?

 

[lexpatrie]

It's technically a cantilever so the deflection check probably is a bit funky or inaccurate in ETABS. I don't use that program much and never liked the non windows GUI anyhow.

 

[jayrod12]

I would probably run some hand calculations to confirm the diaphragm deflections, but I don't see an issue necessarily. What are your bay widths? 25'? so you'd have you braced core measuring 100'x150' and cantilevering 25' on each side? Proportions seem within range.

 

[SocklessJ]

@lexpatrie
I agree with you on the ETABS GUI. I’m never quite sure if ive selected a member or not. It also crashes frequently. I’m a RAM elements fan myself but its not quite as powerful for building design.

@jayrod12
Good call. It’s always good to verify with a hand calc when trying something new.