Twisted high-rise 2

[EEJaime]

All,
Just a general question that came to mind as I was reading today of a high rise residential tower that opened in Dubai, where each floor has a 1.5 degree twist from the floor below. this results in a total of 90 degrees of twist top to bottom. Quite a striking structure. It struck me that the connections floor to floor must be quite different from a normal vertical load transfer connection. Is there large lateral components to the loads as these connections get further skewed as the twist increases?

Just a curious non-structural engineer admiring advances in engineering.

Regards,
EEJAIME

 

[msquared48]

Yea. We, as structural engineers, have to solve the problems of a lot of twisted Architects.

Mike McCann
MMC Engineering

 

[EEJaime]

That's the truth,
Worked on a team for the LAX Tom Bradley Terminal expansion with enormous, "wave" shaped moment frames that spanned large distances with a radiused top member and framed a 90 foot atrium. The structural guys had to build huge scale models and have them shaker table tested just to prove the structure to the AHJ as there were no historical data or information in the Code to justify the connections and member sizes. I remember the SEOR pulling his hair out after many meetings. Do all SE's walk out of meetings shaking their heads and mumbling?
Regards,
EEJaime

 

[msquared48]

Only when there are Architects involved...

Mike McCann
MMC Engineering

 

[dcarr82775]

Especially the architect on that LAX project. He has an unbelievable ego, even for an Architect, but he does wear a lot of black turtlenecks so at least he fits the stereotype.

 

[EEJaime]

dcarr82775,
Now THAT is funny. Runs meetings like a kindergarten class. Amazing.
EEJaime

 

[OHIOMatt]

For some of the erectors that I have worked with, 1 1/2 degrees is with-in tolerance. I guess by that logic, I have several "twisted structures" out there.

 

[delagina]

Structural Engineers dont get due credit though.
It's easy to draw structures with irregular shapes that looks pretty but to prove it will be stable thru calcultion and math...

 

[ztengguy]

Its our job and we get paid to do the design. We dont need a plaque with our name on the building, just a check with our name on it, and the next project.

 

[EEJaime]

CNN has some pictures at CNN-Twisted Tower. It looks so unstable. I wonder if it would meet California Seismic criteria?

 

[hokie66]

A description of the structural system, by the design engineers:

http://www.cement.org/buildings/buildings_mixed_infinity_tower.asp

 

[delagina]

@ztengguy, getting due credit doesnt just mean a plaque with your name in the building.
many structural engineers are underpaid compared to architects.

 

[EEJaime]

Hokie66,
Thank you. Very informative article. I would not have guessed concrete construction. I would have guessed steel, some kind of braced frame. I guess that is why we leave that sort of thing to you structural experts. Just seems counter-intuitive.
Good day,
EEJaime

 

[hokie66]

EEJaime,
The material used, steel vs. concrete, depends to a large degree on the location around the world. Concrete technology, with high strength concrete, prestressing, etc. has developed to the point that concrete is often competitive with steel for high rise construction.

 

[EEJaime]

That is amazing to me because the mass at high elevations would seem to be detrimental to the footing design. Especially with a design that makes even wind load calculations a challenge. Do you integrate the wind for theb90 degree rotation? That needs a wind tunnel test!
EEJaime

 

[msquared48]

And the Architect committed.

Mike McCann
MMC Engineering

 

[EEJaime]

I just can't see this as a stable structure! It seems so "what were you thinking"? Kind of special.
EEJaime

 

[hokie66]

EEJaime,
Probably did have a wind tunnel test, which is common for high rise structures. When wind tunnel testing is done, it often reduces the required wind loading based on prescriptive codes. The mass helps to resist overturning due to wind.

I agree that the structure is a monument to someone's monumental ego (could be the architect or the owner), but with today's computing capabilities, it does not present particularly challenging structural problems.

 

[Robbiee]

hokie66,
Good article, but did not mention the torsion on the core due to sloped columns. I think that would be one of the design challenges.

 

[BadgerPE]

"And the Architect committed."

This is one of the few times that I have to disagree with you, respectfully of course. In this case, the architects and SEs had to be working closely to achieve the common goal, just like the Burj Khalifa. I feel as though while architects can be a major pain in the ___, they also get many of us structural engineers to think outside the box while producing some amazing visual structures. While more efficient, cost effective structures would typically be present if the look of the building was dictated by the SE, they certainly may be less desirable aesthetically speaking.