CMU Shearwall and Steel MF

[StructTaco]

I'm designing a two story cmu building with masonry shearwalls on 3 sides and a steel MF on the front of the building. The diaphragms are flexible and framed with open web joists with LVL top and bot chords. It's a box.

Any thoughts on detailing at the corner where the CMU meets the steel MF? Deflection Compatibility? Do I attach the steel columns to the end of the masonry wall and let the masonry go along for the ride out of plane during a seismic event?

Any help or direction would be appreciated.

Thanks, Taco

 

[msquared48]

The wall is going to go where the diaphragm and frame go. Consequently, I would be worried about pounding of the CMU against the frame if too close and not attached.

So, either butt the frame to the CMU and attach the two, or separate the frame from the wall sufficiently so that pounding does not occur.

Mike McCann
MMC Engineering

 

[StructTaco]

Thanks Mike, I attached the two at the floor and roof diaphragm level, and then separated the CMU from the adjacent building to account for pounding.

 

[Gumpmaster]

Is your diaphragm really flexible if you have a moment frame on one side? Seems like in that case, it's closer to rigid.

Make sure your moment frame deflections are small enough that it doesn't destroy your CMU wall where they connect.

 

[StructTaco]

Where would I find allowable deflections for a cmu wall out of plane?

The diaphragm is wood, over open web trusses (wood chords with steel web members), no concrete overlay, so flexible diaphragm with an OMF with essentially elastic response.

Thank you very much for your response.

 

[seny]

how far is your moment frame from parallel cmu wall - plan dimensions, seismic & wind zone?
for only two story building i would say these are the main questions to know, before making any suggestions. for particular cases moment frame even w/ flexible diaphragm may be not required - three walls c-shape could be enough to govern lateral.

 

[StructTaco]

the building is 50'x80', 2 story. The moment frame is on the front of the building (50' dimension), the parallel shearwall is 80' away at the rear of the building with some openings, and the side walls are 80' long and solid, no openings.

Seismic is SDC 'D', V=0.206, seismic controls as wind can only contact the short dimension of the buildings, basic wind speed is 80 mph.

 

[seny]

as i understood mc frame is along short dimension.
you do not care about out of plane stiff of walls - i would have enough rigid frame to try redistribute at least 35-40% of lateral load, in my opinion it is more economical than try to have rigid diaphragm in your case.