Core walls Reinforcement of 15 Story Building

[Robert-32]

Dear Colleagues,

From your practice, what is the predicted reinforcement of core walls of (25-50 cm)width of a 15-story RC Building in a seismic zone with z=0.3g?

 

[jittles]

Yes, reinforcement predicted to be required.

 

[Aesur]

Infinite... Your walls will be significantly thicker if designed to US standards..

 

[jayrod12]

Infinite... Your walls will be significantly thicker if designed to US standards..

Really? I would say that would depend on the amount of walls. We've had some 15-16 storey buildings come in within those ranges. Granted we're low to non-seismic.

 

[Aesur]

Really? I would say that would depend on the amount of walls. We've had some 15-16 storey buildings come in within those ranges. Granted we're low to non-seismic.

The OP did say "core" so I did make the assumption that this building won't have a lot of concrete walls.

 

[Greenalleycat]

This is an impossible question.
There are so many factors that influence the reinforcement required in a building of that scale that there is no way to generalise an answer with any meaning

- What is the weight of the building (floor type will influence this, live load, cladding, I did a 15 storey building with green roofs at the 8th, 11th, and 14th floors that weighed a shit ton)
- Core dimensions (wall length, and giving a thickness range of 250mm to 500mm is rather significant variation)
- Dimensions of other walls (if present) that will reduce core loads
- How regular/eccentric is this building - torsion will hugely increase loads
- Is this a ductile design or elastic? Are you using dampers or isolators?
- What is your foundation system?
- What is your soil type (affects seismic loads)?
- What is your building period (this is a function of many of the items above and again, will affect your building loads)?
- Is your building drift governed or strength governed (mine was drift governed)?

 

[Robert-32]

Thank you Greenalleycat for your reply. It will be a long answer to your enquiries. Regarding your project can you give me an example of the reinforcement of wall in core? Like 400mm thick wall with 2T20@150mm vertical rebars and 2T10@200mm horizontal bars.

 

[milkshakelake]

OP is looking for a ballpark. Maybe did a calculation and wants to see if it's sane.

I don't use metric, so in the US, it would be something like 18-24" thick with vertical (2) #11 @ 6" and horizontal (2) #7 @ 9". Reduce rebar as you go up. Obviously, this can vary dramatically with the spans, size of building, seismic/wind loads, etc. Tallest I ever did was 14 stories and it used 8" thick shear walls, but there were lots of them. If I remember correctly, it was using #11 @ 4" vertical or something (don't remember horizontal). Seismic load was extremely low. So...it can be anything, basically.

 

[Greenalleycat]

Seismic load was extremely low. So...it can be anything, basically.

This is my point haha
The building I worked on was in a similar seismic zone (the hazard factor here is 0.30, PGA in Class D soils 0.336g) but I don't even know if the seismic load calculation is the same thereafter so the end design loads may be way different
But I can't even remember what reinforcement we were looking at - it got nuked by Council after the concept phase and it was 6 years ago at a different firm so I can't even find the details