Modelling shear wall and steel columns

[JnT_C]

Hi everyone,

First time poster but long time follower.

I'm trying to model shear walls in ETABS to be the SFRS in one direction of my building (located at the perimeter) while steel moment frames are the SFRS in the other direction. The building is only one bay wide in the direction of the shear walls therefore at the corners of the building, the steel frame and the shear wall meet. These steel columns will not be part of either SFRS and so I would like them to be strictly gravity columns. As such, I have reduced their stiffness using stiffness modifiers in the lateral model of my building. However, they are still seeing axial forces when subject to EQ loads in the direction of the shear wall (negligible shear and moment which is all taken by the shear walls). My thought is that under EQ load only (no combinations), these columns should not see any axial load effects. Is this correct or am I missing a fundamental understanding of the structure? The walls are modelled to the same gridline as the columns but should they instead be modelled with a gap between them and the column centerline (as it would be in reality)? I tried this and the axial load acting on the columns significantly reduced but I'm not sure if this is the correct way to model the behaviour or if it's a "lucky" cheat.

Thanks.

 

[KootK]

Is this correct or am I missing a fundamental understanding of the structure?

That is correct.

The walls are modelled to the same gridline as the columns but should they instead be modelled with a gap between them and the column centerline (as it would be in reality)?

That is a common approach and a fine idea.