IBC 2000 Seismic Application

[JAE]

Alright - here's the question - In the IBC 2000, there is Chapter 16 that outlines the seismic loads for buildings - these are based on an R value which is based on the type of structure. The end of the Table 1617.6 has a part 7 - "Steel systems no detailed for seismic" - so far so good.

In Chapter 22 (steel) the section 2212.1.1 calls for the use of the AISC Seismic Provisions to be used for SDC A, B or C IF you use any of the R values from Table 1617.6. It then says that IF you use the part 7, "Steel systems no detailed for seismic", you can use R=3 and then NOT use the AISC Seismic Provisions.

I can follow that, too.

Now in the AISC Seismic Provisions, Section 1.0 "Scope" immediately says that, "These Provisions shall apply to buildings that are classified in the Applicable Building Code as Seismic Design Category D and higher..."

So I guess the IBC was written later than the AISC Seismic and inserted the use of SDC A, B and C buildings into it, with the only OUT being the use of R=3.

Do you agree? Thanks for any responses.

 

[Taro]

Sounds right. The building code often adopts reference standards with some amendments.

 

[TFL]

interesting .... i had not heard that. thanks!

 

[haynewp]

Yes I agree and this is what I have been doing and what the building departments require in my area.

I talked to AISC solution center about this before and they told me that the AISC provisions were not originally intended to be used for buildings in class A,B, or C as stated in the scope you quoted from AISC. The IBC has imposed the strict R=3 limitation anyway as the only way out of it, I don't know why.

The AISC engineer also told me that usually, you will come out cheaper by just using the R=3 than going through the AISC provisions for class A, B, or C while using a higher R. Keep in mind this was one person's opinion and there seemed to be exceptions as he eluded to. I don't have enough experience with the provisions to give you my opinion, I usually am designing for class C and just use the R=3.