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RE: New Openings in (E) CMU/Concrete Bldg

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For openings in existing CMU, I reinforce the top of the opening before
cutting the opening, to avoid the unreinforced CMU from being loaded as a
lintel from the weight above without support below. I show an angle at each
face of the CMU above the opening, with its outstanding horizontal leg
extending into the mortar joint below the CMU to be supported, i.e. the
mortar joint to be routed out for installation. I extend the angle beyond
the opening on each side for support by the adjacent full height block. I
also bolt the angles into the CMU with drilled-in masonry anchors.
Sequencing is covered by drawing notes. This provides a flush metal support
without outstanding flanges. 

> -----Original Message-----
> From: HariA [mailto:haria_pe(--nospam--at)]
> Sent: Wednesday, April 25, 2001 2:12 PM
> To: Mail Server @ SEA International
> Subject: New Openings in (E) CMU/Concrete Bldg
> Hello:
> Wanted to get an opinion on the design of new wall openings 
> in existing
> conc/cmu building.  The general method used in our office has been to
> provide a frame around the opening ie., about 6" beyond the 
> opening on top
> and two sides.  Angle at the top anchored to the wall and 
> strongback running
> from floor to roof.  The angle takes the vertical (based on a 
> triangular
> load) from the wall and roof above while the strongback transfers the
> vertical to the wall and also acts as a strongback to take 
> the out-of-plane
> lateral forces of the wall.  The architect is not too much 
> for this design
> since steel is going to be visible all across the wall.
> But I have seen other engineers put a channel around the 
> opening which fits
> into the door or window rather than on the wall.  How 
> effective is this for
> the lateral forces.  Building we desing are mostly in the 
> southern calif.
> Thanks for your input.
> Hari

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