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Re: steel frame with masonry infills

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Alex

You have the keywords in your post: "Seismic Zone 4" &
"A school". And it is a school, man.  In US codes your
are probably forced to do ductile design of such
frames in such zones. 

If I were you I would elect not to attach any  infill
to the frames, and I would utilize a conservative
ductile frame design. Infills are terrible and I
believe your specification is right on suggesting you
leave a 1/2 "" gap.

I am not sure you can call that "dual". "Dual" may be 
taken to mean "frames sway and shear walls deflect".
Do you have this basic behavior with infill between
columns?

For a school I might as well go on add some braces or
a serious ductile RC shearwall.

Good luck
IJR 






--- Nacionales Alex <acnacionales(--nospam--at)yahoo.com> wrote:
> Hello.
> I am the project engineer for the owner of a four
> storey steel framed school building with 6" CHB
> walls.
> 
> The building is about 12M wide and 62M long and 14 M
> tall.
> The frame is a special moment resisting space frame
> and we are in seismic zone 4. I have little design
> experience in steel framed buildings but I believe
> that a dual system would be more economical here
> where
> a load bearing 6" CHB wall could act as shear wall.
> 
> The design specifies that the CHB be laid 1/2" from
> the steel columns and shall have 1/2" thick styrofor
> to fill the gap. I find this to be unnecessary. I am
> aware that masonry infills specially where there are
> low windows can interfere with the frame action as
> observed in RC construction in the past earthquakes
> but RC columns can be designed against this by
> providing more shear reinforcement above the window
> level, for steel columns its different because the
> section is the same for one length so the design for
> maximum shear at the base of the column should be
> sufficient.
> 
> I would appreciate some comments on this. Thanks.
> 
> Alex C. Nacionales, C.E.
> 
> 
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