Special concrete moment frame

[Oversee]

We are designing a concrete building to SDC C (IBC 2003). From Table R21.1.1 of ACI 318, an intermediate moment frame system is expected. This allows the use of two-way slabs without beams in Cl 21.3.6. My question is: will it be acceptable to use concrete shear walls as the only seismic-force-resisting system? Columns and flat slabs are to be designed to withstand permanent loads only. Thanks.

 

[JAE]

You might clarify - you say you are using an intermediate moment frame but then ask about shear walls. Which is it to be?

According to 21.2.1.3, if you use shearwalls, they do not have to meet chapter 21 unless you use "special" shearwalls.

 

[Oversee]

Thanks Jae

My question was coming from Table R21.1.1, ACI318-2008. Clause 21.3 (intermediate moment frames) is required as the frame members in column where SDC is equal to C. I want to use shear walls, instead of intermediate moment frames, and wish to know if this is okay. Please see attachment.

 

[mmillerpe]

I would interprete ACI 318 to mean if you are using intermediate moment frames as your lateral load resisting system, you need to meet section 21.3. Since you are planning to use shear walls you do not have intermediate moment frames as part of the Seismic Force Resisting System, you are not required to detail the frames per section 21.3 requirements. You would need to make sure that you design for the proper R, Cd, and Omega factors per code for the shear walls.