ACI 350 / ACI 318 Guidance on Locally High Shear Results ?!?!?!? 1

[Struct_Dre]

Hello All!

When using finite element analysis (RISA 3D) to analyze underground concrete tanks, I often get abnormally high shear results at the corners of the tanks. The plate forces at the corner plates will typically be substantially larger than the adjacent plates. Very early in my career, I was shown a passage in the ACI code which says that the shear can be taken at some distance away from the corner to be more accurate, b/c the high shear results tend to be inaccurate. I was shown the section in ACI years ago and I have not been able to find it since.

Does anyone know where this is located in the ACI code? Or does anyone know of a definite formula to follow in this situation? I was basically taught a rule of thumb and I would like a concrete way to address this issue that arises constantly.

Any help is appreciated!

 

[KootK]

Could this be as simple as just the business where we take the maximum shear to be the value at "d" away from the supports? If so, this would apply only to net inward pressures.

 

[Celt83]

Here is a screen cap of the commentary sketches for the critical section:

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[GC_Hopi]

Have you tried adjusting the meshing to provide a finer mesh in these areas of high shear. This usually resolves this problem or at least shows that these stress concentrations are a byproduct of the FEA and not a true stress concentration. Also if you average out the shear results locally do these high values disappear. That is another sign that the meshing might need adjustment.

 

[WARose]

Smoothing stress concentrations (if it is indeed a concentration) takes some seasoning as a analyst. You can search on here for more info.

 

[Struct_Dre]

Thanks everyone!

 

[Struct_Dre]

@GC_Hopi Yes! That is what I typically do. Thanks for the feedback!