NCEES Practice Exam Question

[tfoy]

I have a question about the solution to problem 601. About 1/2 way down the page, when calculating the effective height of the wall, a k factor of 2.1 is used. I looked in the masonry code as well as my Amrhein book and both say to use 2 for a fixed/free condition. Any insight as to why NCEES is using 2.1 in this case?

Thanks,

 

[TehMightyEngineer]

Are you sure they're not stating 2.0 for a fixed-free is the theoretical K, not the recommended design value. ACI and AISC both recommend K = 2.1 to account for the fact that we can't truly make an ideal fixed connection. I personally would use the more conservative and realistic value of K = 2.1 as the solution did.

 

[tfoy]

Yes, I'm sure of it. Take a look at Figure CC-1.14-1, page C-43 in the ACI 530. It shows that h>=2*Height. So k=2.1 isn't wrong it's just arbitrarily not right.