Pier Stiffness for High Rise Buildings
Pier Stiffness for High Rise Buildings
(OP)
Just out of curiosity...
When modeling concrete core wall for a tall building, I would assume you would need to model the foundation stiffness, pier stiffness in compression, and pier stiffness in tension when checking serviceability requirements such as deflection and accelerations.
Is it typical to assume that the entire pier length is cracked under tension loads? So your axial pier stiffness in tension is effectively the stiffness contribution from the pier steel alone over its length? This seems to be quite conservative since by the numbers, large piers with much reinforcement will have a large effective area and can support quite a bit of tension load before cracking. Any thoughts?
When modeling concrete core wall for a tall building, I would assume you would need to model the foundation stiffness, pier stiffness in compression, and pier stiffness in tension when checking serviceability requirements such as deflection and accelerations.
Is it typical to assume that the entire pier length is cracked under tension loads? So your axial pier stiffness in tension is effectively the stiffness contribution from the pier steel alone over its length? This seems to be quite conservative since by the numbers, large piers with much reinforcement will have a large effective area and can support quite a bit of tension load before cracking. Any thoughts?






RE: Pier Stiffness for High Rise Buildings
Otherwise yes, column type elements should be substantially reduced in stiffness for tension cases to account for cracking. I don't think there is a rule but I have seen numbers usually a bit higher than the effective area of steel alone but still highly reduced.
RE: Pier Stiffness for High Rise Buildings
I've never been involved in the design of a super tall building. Based on the case studies that I've read, however, it seems common to include soil stiffness interaction. It's also common to have something akin to an outrigger system to increase the effective depth of the building and address the concerns that Bookowski mentioned.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Pier Stiffness for High Rise Buildings
I appreciate the feedback.