Composite CMU/Brick wall Expansion Issue

[RareBugTX]

Hi:

I would like to know if anyone has dealt with this issue before.
In designing a CMU/Brick COMPOSITE shear wall,(intermediate space fully grouted) how have you dealt with the different coefficients of expansion of the two materials. We know there's a lot of potential for cracks but I haven't seen this issue addressed in any of the books I have in my structural masonry design books.

Thanks for your feedback beforehand.


RareBug

 

[samdamon]

rarebug- How tall is your shear wall? Is it existing or new?
I'd also be concerned about moisture related shrinkage in the block and irreversible moisture expansion in the brick, if your walls are new. Regards

 

[RareBugTX]

samdamon:

Wall 50 ft tall, new construction. Clients wants brick on the outside and I am using my reinforced CMU for structural purposes.

Thanks

 

[ArneG]

I haven't seen any plans for a brick/cmu building without an airspace and insulation for a long time.

You may want to rethink the wall construction and recommend a cmu structural wall with a layer of insulation, air space and veneer face brick attached to the masonry with eye and pintel type masonry ties.

50' is pretty tall for face brick without a brick bearing angle and properly detailed relief jointing. I usually detail brick relief joints every (2) stories on buildings (3) or more stories high (every 25' vertically +/-).

I would definately not recommend tying the two courses together hard at that height.

So your issues are:

1) Differential movement
2) Moisture transmission
3) Air quality (mold) due to moisture transmission
4) Insulation

Sounds like you need to specify a cavity wall system. Talk to the architect of record and see what they think.

 

[connect2]

yes the two should be treated separately, everything being connected so to speak and in the end not separate actually. At that height the veneer will need to be supported on the shear wall which will require that its, the shear walls, deformation characteristics for lateral loads be determined so that movement joints be properly detailed for the veneer and its, the veneers, movement requirements. Issues of clay expansion and concrete shrinkage, thermal loads, lateral loads, moisture movement, etc. all being related to performance over time and in the end connecting them all.
We note that these issues are often not well connected, with regards to the veneer especially, often resulting in premature failure of the veneer system and deterioration of the structural system supporting it.