Please can you explain the implications of proceeding with the design of anchors using CBFEM in Profis where the results are very different to those calculated assuming a rigid baseplate? I understand that flexibility in the plate can result in significantly higher stresses than for a rigid baseplate in the anchors, concrete and steel elements, but if CBFEM has been used to calculate the forces in the anchors assuming a flexible plate, it's unclear to me how the anchor design would be invalidated by lack of similarity to rigid baseplate results.
To a lesser extent, the same question applies to the design results for the baseplate, stiffeners and welds when using Profis Premium - if CBFEM has been used to more realistically reflect the effects on the different components when consideration of the plate flexibility has been included, can the results be relied upon even if there is a significant difference compared to the rigid baseplate results?
I have read through the following web pages and guide, but don't believe the above queries are explicitly addressed:
https://www.hilti.co.nz/engineering/article/why-its-important-to-check-the-anchor-base-plate-rigidity/wymrse
https://www.hilti.co.uk/engineering/article/how-to-assess-if-the-baseplate-can-be-considered-close-to-rigid-by-engineering-judgement/qass0a
https://www.hilti.co.uk/engineering/article/technical-background-on-the-advanced-baseplate-feature-of-our-anchor-software-profis-engineering-par/ymhz59
https://www.hilti.co.uk/engineering/article/technical-background-on-the-advanced-baseplate-feature-in-profis-engineering-part-2/bfjd0l
https://productdata.hilti.com/APQ_HC_RAW/ASSET_DOC_23126683.pdf
Thanks
Hi, thanks for the posting there are a number of topics here. Ok I’m assuming you have run a design check with one that gives ‘X’ load on an anchor based upon a ‘rigid’ plate then’ Y’ load on the same anchors from the CBFEM. I see that you have an understanding of why this happens but as a brief recap due to concrete non-linearity.:
Difference between CBFEM and Rigid
Assumptions behind rigid
- Linear anchor steel stiffness (dependent on Anchor Diameter & Elasticity Modulus)
- Linear steel
Assumptions behind CBFEM equivalent to rigid
- Non linear anchor stiffness from tests (product & load dependent)
- Linear steel with a very large elasticity modulus
So the results are not the same.
Difference between CBFEM rigid thickness and the aboveassumptions
With the non-linear behaviour of the steel creating differences between rigid thickness of the above assumptions which can happen for edge cases.. I hope this answers the first part of your question.
Regarding the second part of your question when you run the CBFEM you have the results compared side by side with any % variation . Now if you are above a certain % range (Approx 12-15 %) you’ll be prompted by the software that you are authorizing the software to carry on with the calculation even though the deviation is outside of the scope of the anchor design. So if you amend the details so this prompt does not occur then the results are fine and HILTI will stand by those results otherwise you would be using your own engineering judgement.
I’ve also attached a publication published by Stahlbau which combines your attached links into one readable pdf format.
