Masonry Wall

[ENGJP22]

Hi guys, I have an existing masonry building and the cliente wants a second floor, I have this case where the new wall its going to be above the existing slab and I want to know how can I reinforce the slab so there wont be problem transfering the new loads, thanks in advance.

 

[dik]

Can you put a steel beam underneath the slab, in line with the wall? Can you temporarily shore the slab reinforce the new CMU wall to act as an upstand beam? Lots of possibities...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[ENGJP22]

I cant put an steel beam but I can shore the existing slab to create the upstand beam.

 

[Enable]

Reinforcing the existing slab: (EDIT - FRP) is an option. Another option is doing underside repairs full length and installing more / larger bars in line with the wall or perhaps even through slab which would allow you to create a beam in-slab.

Other Options: dik mentioned a few good ones. But you could also put a steel beam at the bottom of the CMU wall (directly on top of the slab) and encase it in concrete. Run it from support to support. It'll just look like a concrete curb yet do most of the heavy lifting so the slab can stay as is.

 

[ENGJP22]

Hi Enable, what does RFP stands for?

 

[Enable]

Yikes that should have read FRP HA! It's carbon fiber reinforcing. See here.

 

[ENGJP22]

Ok! Got it! If opted to do and uptand concrete beam (inverted beam) that wouldn't create a negative moment in that point?

 

[dik]

Design the new upstand to determine the amount of reinforcing... check for shear... provide shoring for the slab, put a CMU 'U' block for the first course and add flexural reinforcing... add however many regular CMU courses over. You might consider adding 1/4" or #3 deformed hairpin bars for shear. Fill courses with PCC grout... You can chip out the web a bit and place a couple of smaller bars for reinforcing the upstand beam... build balance of wall. Leave for a week and carefully remove shoring from slab. Check for any distress. Make sure the upstand beam is sufficiently connected to the CMU walls on each end... done like a turkey...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

You could also provide anchors from the slab to the upstand... just thought of it...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Enable]

You'll certainly change the behavior of the slab. That isn't necessarily a problem though. You just need to identify the ways in which the load path changes and see if the existing can accommodate such a change (e.g. has bars at the correct location and orientation). To be clear you need to analyze both directions (not just the plane of the wall direction).

If you go with my steel beam idea it will be independent of the slab so you won't have to reanalyze the slab in the same way. Either should work just fine.

 

[dik]

Enable... a steel beam would have been my first kick at the cat...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Enable]

Yours was underneath and was said to be untenable presumably for headroom issues. I stole your idea and said put it on top!

 

[ENGJP22]

Yes, thats the case in that location where the new wall its going to be there isn't any negative flexural reinforcement.