Composite CMU & Brick Shear Wall Question 1

[RareBugTX]

Has anyone looked at the differential coefficients of expansion for composite shear walls of cmu and brick? In my design there is mortar and reinforcement in the space between the cmu and brick. I have looked at the design procedure in The Masonry Designers Guide, but I have not seen this potential problem addressed anywhere. I think there is potential for cracks for differential movement.

Any thoughts will be appreciated.

 

[civilperson]

Each joint in masonry is a crack/expansion joint. Wythes tied together for sixteen centuries have withstood the differential expansion of a variety of masonry types successfully. Good material for a thesis.

 

[RareBugTX]

I see the point, now, if every joint is an expansion joint (every course of masonry) does that still apply to wythes of different masonry material?


Thanks

 

[concretemasonry]

It certainly is a subject for a thesis. You have 4 different materials (clay brick, CMUs, mortar and steel)

It is a rare construction method today since you can get very high structural performance out of the CMU wall.

Is this an analysis of existing or new construction? Is it a masonry wall with a reinforced cavity and two different exterior structural masonry materials or is it a reinforced CMU wall with a collar joint?

The mortar is a very minor factor in the strength of CMU walls and in the strength of brick walls.

The brick, mortar and CMUs have reasonably similar coefficients of expansion for temperature. If you have a wall with significant dimensions, the only material property conflict I would be concerned with would be the difference between the long term expansion of brick and the shrinkage of the CMUs. In the case of using brick veneer on a block or steel structures, there are limitations on maximum length or heights of the brick portions of the walls.