Stair wall subject to lateral load

[tngv752]

Hi

I am modelling a 6 storey building using Etab (21m high). I modelled the stair walls and core walls using wall pier and spandrel around the openings to take vertical and lateral load (wind and earth).

Please see the attachment for the load applied on the wall pier at Level 1. The moment from earth load (91KNm) is quite high for pier (250mm wide x 150mm thick).
Heavy reinforcement must be used in this pier.
My question:
Any thing wrong in the way I modelled and give this load to the wall pier ? This load is reasonable ? If yes, then use heavy reinforcement in this pier.

Thanks

 

[rowingengineer]

Is the scale of your sketch correct because normally you have a fair bit of wall from your door to the end of the stairs in a stair well, looks more like a elevator shaft. I can't comment on the modelling in etabs, but if the scale is correct I would include coupling beams.

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[tngv752]

Yes, it is the right scale. Of course, I have coupling beams on top the openings. These beam sections are big enough for using conventional steel reinforcement.
But the pier I mentioned has a small cross section because the opening is too close to one side (It is the stair way not elevator). I look like that I have to use a steel I-section inside the concrete pier (composite column) to resist high bending moment.

 

[asixth]

If that core is properly meshed then the end walls would act as flanges and the forces would be predominatley tension or compression and it should be designed that way.

 

[KootK]

I'd not include the 250 return in the model. You're not going to be able to couple on that side of the opening anyhow. Otherwise justify a reduced cracked stiffness for the pier to bring the moment down. The composite pier seems extreme, especially in a 150 thick wall. I'd double check the thickness anyhow. I'd be surprised if you're not exceeding some slenderness ratio.

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