Shear Wall Reinforcing for an Existing CMU Wall

[dhesington]

Does anybody have any recommendations for providing both vertical and horizontal reinforcing to existing CMU wall without making the wall look like swiss cheese? The existing wall is unreinforced and has no horizontal joint reinforcing. Really don't want to have to saw cut at 48" each way.

Any other ways to meet shear reinforcing requirements?

FYI also needs to meet requirements of a specially reinforced wall in seismic cat D

Thanks in advance...

 

[MiketheEngineer]

That is a problem. Assuming expense is not concern - check with fiber/epoxy guys. You might be able to "coat" the walls and get what you need.

 

[dhesington]

What about carbon fiber strips? And if so does anybody have ideas or recommendations where I can find the structural design properties or how to equate it to steel reinforcing?

 

[OHIOMatt]

I have a few questions:

1. How will you get shear resistance at the foundation/wall interface? Drill and epoxy? This would require a substantial hole in the wall to allow for the drill.

2. How will you get sufficient end anchorage?

3. Is the footing designed to support a shear wall?

By the time that you adress all of the concerns with a shear wall as required, it would likely be better and less costly to replace. Likely would require some shoring etc. This would allow you the chance to look at the shear transfer into the wall as well.

 

[shaneelliss]

ACI 440.2 (Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures) is a good source for designing external fiber reinforcement. The guide was written for concrete, but I think the principles and design strengths of the fiber/bond would be very similar for masonry.

 

[TXStructural]

How big is the wall? Do you have access to ends or top of the wall? Is it grouted or just standard mortar joints.

Demo and replace would probably be the least expensive option, based on the amount of labor it will probably take to retrofit reinforcement.

A company I worked for some years ago had to retrofit reinforcement into all walls of a school gymnasium, but it was already fully grouted and included a lot of wall area. Retrofit likely cost about as much as the original wall, but there were other dependencies on the project which made demo a poor option.

 

[a2mfk]

Hmmmm, swiss cheese, preferably on ham and rye.

Are you worried about the structural integrity of the wall while the sawcut faces are removed and rebar is being installed? Or is this an aesthetic issue that stucco could probably cover?

Mr Texas makes a good point, what is going to be more economical? I have added a lot of vertical rebars in CMU where it was more economical, but for wind loads only so no intermediate bond beams. In my experience adding rebar is not very difficult but is labor intensive, but many times will work out to be the best solution.

But I think carbon fiber is an interesting solution and have wanted to use it on a project but have not had the time where it was the best choice yet.