#### vishalselvan

##### Structural

I am trying to analyze a building that has both steel framing for the first few floors and is then continued upwards as a concrete structure. I was able to use AISC's direct analysis method to check the deflections in the steel framing and check the members for strength using reduced EI properties.

When I get to checking concrete, the code doesn't give an explicit method on how to do something similar to that shown in AISC. My understanding is that I can use moment magnifiers or run the analysis with P-delta turned on. My goal is to analyze the entire model in one fashion, and I'm interested in finding out how to analyse the concrete structure with P-delta.

1) Would sway/non-sway not matter when P-delta analysis is done? In AISC, they mention that k=1 in P-delta analysis.

2) Is there an equivalent for the iterative method to find EI for steel for applying to concrete? I found that the material non-linearity is accounted for in Table 6.6.3.1.1 (c) (ACI 318-14). I am not sure if there is another reduction that I need to apply.

I'm using RISA 3D to perform the analysis. I would appreciate any help as I do not have a lot of experience in dealing with concrete structures.

Thanks,

Vishal