Reinforced brick wall?

[WWTEng]

I saw a set of drawings yesterday where the engineer showed rebar between the brick wythes. Its a 4 wythe brick wall with #4 @ 24" oc. I am not sure if you can reinforce brick wall, I mean basically the rebar will be jammed within the grout so its not going to do any good whatsoever. I am not sure if the intent is to use the rebrar as hold downs (will try to find out today) but rebar within mutliwythe brick wall just seems like a bad idea.

Thoughts please!

 

[MiketheEngineer]

Maybe not a bad idea - but maybe dumb idea!!

 

[ishvaaag]

Not that it is a "good" detail for very engineered structures but may fill some needs ... for the case shown in fig 3 of

http://www.staff.city.ac.uk/earthquakes/MasonryBrick/ReinforcedBrickMasonry.htm

they seem thought to be good in UK for sites where earthquake solicitations may be relevant.

All this needs to be looked with the ruling code in sight.

 

[concretemasonry]

A 4 wythe wall? - What is the total wall thickness?

Since there are many sizes of "brick"? What is the nominal or actual brick unit thickness.

Reinforced brick can be very effective as long as it does not have too many wythes (usually an inner and outer wythe) and a small area for fine grout to bond the reinforcement to the the two wythes so the wall acts as unit and a few pieces of different materials stuck together. The concept of using hollow brick is also valuable.

There are some special brick units that are available that allow reinforcement in the outer wythes plus a narrow "collar joint".

A good engineer can make it work with the constrictions imposed by the material selection that may often be based on exterior appearance.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[WWTEng]

cm, the wall is 1'-8" thick. Its a 8'x8' square smoke stack. Topped by steel cap. I don't see any structural reason for rebar, the mortar seems to have adequate tensile strength for the wall to span horizontaly (there is also horiz reinf ladder @ 16" oc vertically). And in terms of overturning (shear wall action) there is no overturning.

The grout gap between the bricks can't be more then 1 7/8", I can't imagine a rebar getting and sort of bond. I think the engineer is just being conservative.

And is case you are wondering why such a thick wall, it matches the existing 100 year old wall below the roof.

 

[WWTEng]

And the brick is 4" nominal.

 

[JAE]

Perhaps the rebar was a "feel-good" addition to the design - not based on the need for overturning.

 

[WWTEng]

JAE,

Thats what I think. But I am wondering if it will do more harm. Without enough concrete around, could the rebar corrosion be more problematic in brick?

 

[hokie66]

If it is a smokestack, why do you say there is no overturning? I don't understand why you say that the vertical bars would not bond. In this type wall, the bricks, grout, and bars form essentially a monolithic assembly, just like any other reinforced material. If there is any reinforcement which is likely to contribute to corrosion, it would be the horizontal wire...I would get rid of that.

 

[WWTEng]

Hokie,

Plan dims are 8'x8'. So @ 25 psf wind (no seismic) we are talking about 100 plf line load on the shear wall. Being 4 lines of brick, its heavy enough that there is no overturning.

And thanks for your comment about the vertical reinf. I have never reinforced a brick wall before so I did not know that if its practical especially when the bar is in the grout joint. Your mention of monolithic assembly makes sense to me.

 

[hokie66]

This type wall, with bars in the collar joints, are normally built with the bars embedded in mortar rather than grout. The mason just builds in the bars as he goes. Another way of accomplishing basically the same thing is to build the outer and inner skin, with ties between, then grout.

 

[dhengr]

Over the years we did a lot of walls in the way Hokie suggests, two wythes of brick tied together, with grout and rebar in the void btwn. the two skins. We also used a clay brick product which was made more like (in the shape of) a conc. blk., and treated that essentially like a grouted and/or reinforced CMU wall in its design. There were BIA Tech. Notes (#17's, I think) on reinf’d. brick masonry. We did several 7 and 9 story bearing wall bldgs. using this latter wall system. I also did some high bearing walls, and walls with large arched opening in them with reinf’d. brick masonry. The bigger question might be, is the existing brick wall reinf’d. and how are you going to make the new reinf’g. integral with the existing, so it is meaningful. Also, there can be compatibility issues btwn. the 100 year old brick and mortar and new brick and mortars.