Permanent Bracing Of Exist. Masonry Wall

[Heldbaum]

Hello folks, please see attached sketch of proposed bracing. In a nutshell, my company is taking over the project that was done by other engineer. I already checked the structure of a new building but there is still bracing to be prepared by us. The attached sketch is what previous engineer proposed. Those 3 walls stayed in place and they need to be braced permanently. They can't remove those walls. The height is roughly 33' and the building width is 48 feet, from C1 to C2 is around 18'. The client doesn't want to do RC frame but he wants us to use steel instead. Any thoughts ? How would you brace those walls? Steel moment frame anchored to the masonry with hilti anchors ? And full lateral load on this frame? The wall thickness is 12"-16"..Thank you for any thoughts.

http://files.engineering.com/getfil...-b3c8-4b83-8149-1649d7851d62&file=Bracing.png

 

[Mjkkb2]

SO what is the reason for bracing? Was floor and/or roof removed from inside the building? Is any new floor or roof going back in it's place? Is the wall to be left free-standing? IS it an exterior wall or will it become an interior wall when the new building is built?
I am not sure what the exposure (to wind) is, there seem to be an adjacent building - is it taller than your wall? DO you only need to brace for seismic?

IF you were just to replace the concrete frame with steel, then I don't have a problem with it. A three sided frame system with post installed anchors embedded into masonry to tie it is feasible.
SOme more detail would be halpful though....

 

[JAE]

I think steel framing would work as long as you paid close attention to the potential steel frame deflections and how this might affect the existing masonry.
The bottom "grade beam" might still want to remain as concrete and to create a foundation of sorts for your steel framing above.

If the masonry is old - i.e. with old soft brick and mortar - then you might want to be conservative in your connections using the Hilti HIT HY70 anchors as the Hilti capacity numbers are based on new brick and type S mortar or similar. The uncertainty of the old brick walls would bother me.

Some of those old walls had "nice" brick on the outer layers and junk brick - or broken pieces - sometimes used to fill the voids. Not very competent to anchor to.

Also - at the bottom you show the existing brick supported by existing piling. When excavating down adjacent to the base of the wall, is there a concern that the axial pressure on the piling, and the sudden removal of adjacent, perhaps confining, soils might allow a side blow-out of sorts in the masonry. If so - perhaps a sequential excavation and concrete placement is in order - to allow only limited segments of wall to be exposed at a time - 8 ft. or so?



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[JAE]

I might add that older, softer masonry can probably accept greater deflections than more modern, stiff and brittle masonry.

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[dik]

Careful when you're dealing with historic brickwork... there's a paper on SRE's site that has some useful information and it's titled Historic Brickwork.

Dik

 

[BAretired]

It might be a good idea to inspect the walls if you haven't already done so to see what condition they are in.

BA

 

[Heldbaum]

Thanks guys for all tips.

Mjkkb2 - the old building is being demolished right now and new one will stop at the location of C1 and there will be something like a deck at ground floor level.They can't remove the exist. wall so it needs to be braced at the location of old floors.