Limits on legacy design methods for deep components

[BridgeSmith]

AASHTO has the following conditions for the use of methods other than Strut-and-Tie (STM) for deep components (Article 5.8.4.1):

1) The provisions of Article 5.8.2.6 specifying the amount and spacing of crack control reinforcement are met as a minimum;

2) A limit on usable shear capacity is specified;

3) The loading is placed at the appropriate depth of the component relative to the reactions in a manner consistent with the legacy method being used;

4) The method of analysis reflects the disturbed stress field, the behavior of cracked concrete and other nonlinear behavior anticipated at the strength or extreme event limit states.

I think I'm clear on conditions 1) and 3), but not sure whether 2) just means the concrete shear strength has to be limited to some fraction of f'c, or if there's something more required.

I'm completely lost what is required to meet condition 4)

I don't have access to ACI, which I understand is where this originated, so perhaps there's more explanation there?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[BridgeSmith]

Still looking for some input on this. Anyone?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[HTURKAK]

Dear BridgeSmith (Structural),

I saw your thread some time ago but did not respond since the practice in my region differs.. I am sure you looked to the commentary of that article but i have copied and pasted the same below;

ACI 318- 14 specifies the Dimensional limits (9.9.29) Vu ≤ φ10 (√ fc)bwd , Distributed reinforcement along the side faces (9.9.3.1 ) ..

IMO, if STM method is not preferred, the LEGACY method expressed should be FEM.. There are other methods developed by adopting CIRIA CIRIA Guide 2 published by Ove Arup.

You will find the pdf copy of the same.

 

[BridgeSmith]

Thank you for your response, HTURKAK. We were trying to understand if we could continue using the sectional design approach that we have been, since it has 'served us well'. We are just hung up mostly on what it means by the need for "A limit on usable shear capacity" to be specified. I was hoping the commentary of ACI 318-14 would provide something more specific on what is needed to meet this criterion.

Rod Smith, P.E., The artist formerly known as HotRod10