Deep Beam/Wall - Minimum Thickness & Reinforcement

[Drapes]

Is there any minimum concrete thickness requirements for deep beam/wall design? Can a single layer of reinforcement be sufficient?

Have so far adopted strut and tie method to justify a 150 thk deep wall with a single layer of reinforcement each way without any stirrups, under gravity loading. Looking at adopting a proprietary concrete wall system (AFS or Ritek wall) which will act as permanent formwork (client preference), but unsure if the walls need to have a min thickness and if a singly reinforced deep beam/wall is acceptable?

Also, with these walls attracting equake loads, I have reservations with single layer of reinforcement, as to achieve a certain level of ductility this often warrants boundary elements (with stirrups etc).

Keen to hear other peoples thoughts and experiences on this.

 

[MIStructE_IRE]

I often find that the fire rating requirements will govern minimum thickness

 

[jayrod12]

Our local code requires two mats in walls larger than 8"

 

[Agent666]

In NZ after recent 2011 and 2016 earthquakes our code was amended to heavily penalise the use of singularly reinforced walls as they did not perform as expected in many instances, especially if only minimum longitudinal reinforcement ratios were provided and higher than expected long term concrete strength had developed.

Essentially a single crack would form instead of the expected distributed cracking in a plastic hinge region, due to the reinforced capacity after cracking being lower than the cracking moment of the concrete section. This single crack concentrated the yielding/strains over a short length of the bars and resulted in the bars fracturing after a few cycles.

Also you should see if your code requires checking of the buckling of thinner walls, especially if they are carrying any axial load from levels above.