Considering ULS Displacements of Connected Structure

[Strook]

G'day guys,

Certifying an aluminium lift shaft structure that will be installed adjacent to an existing steel/conc. school structure. The lift is external to the structure and will be used to provide access to disabled. Our client currently manufactures elevator shafts to be fixed off at each floor height back to the school structure.

My question is, is it industry best practice to consider the ultimate limit state (ULS) displacements of the school structure as forced displacements at each floor? This will then put load back into the elevator structure, essentially as if the school structure when moving is dragging this smaller, less stiff structure along for the ride. This seems logical to me, however the forced displacements are introducing significant loads into my client's structure.

The alternate option I see is to treat each fixing point as a fixed point in space, which is great...but unrealistic. The second alternate option may be to design without these connections back to an existing structure and essentially have a free-standing cantilever elevator shaft, however this may create different issues.

Our client has been manufacturing and installing this lift shaft design for years without incident (albeit, I have no data regarding the amount of wind/seismic events that these arrangements have experienced).

Your thoughts and experience would be appreciated.

 

[Strook]

A photo of the structure FYI. Fixing at mid-height, front face.

 

[Enhineyero]

ULS deflection seems a bit overkill to me.

If the school is as tall as the lift, I don't see why deflections would be significant, unless the school structure is using a cantilever column system for lateral force resisting system, look into this.

However, my approach to this is easy and lazy. Instead of designing the lift structure to deflect as much as the school structure, I would create a roller type connection between the lift structure and school structure, roller shall be able to move horizontally to cater for the deflections, then design the lift structure as freestanding/independent. I'm not sure why you say this will be an issue, the picture shows that the lift structure is braced by what seems like tension rods.