Rustication strips on exposed concrete with discontinuous horizontal wall reinforcement

[MonsieurR]

Hi everyone,

I was checking out the book "Architectural Detailing: Function - Constructibility - Aesthetics" by Edward Allen and Patrick Rand, and the following detail related to rustication strips on exposed concrete with discontinuous horizontal wall reinforcement (attached, no copyright infringement intended) appeared:

"As recommended by ACI, we discontinue half the horizontal reinforcing bars at each control joint to help create a plane of weakness"

Does anyone know why on earth would one need to create a weakness plane there? I still haven't figured it out. Is it shrinkage related? Because I was told rustication strips are aesthetically related details only.

Thanks and best regards.

 

[BAretired]

The strip on the upper sketch is not required for shrinkage. It is probably used to hide the pour joint which would otherwise be seen from the exterior.

The lower detail is a plan view near the corner; curtailing half of the horizontal reinforcement and introducing the rustication strips creates a vertical control joint or plane of weakness and is used to prevent unsightly cracking from temperature and shrinkage.

BA