building moving laterally under gravity loads 1

[chekre]

Hi guys,

When core walls location is eccentric and the building is displacing laterally under the gravity loads, is there any limitation to such kind of limitation ?

thank you

 

[Ron]

Geez! How much lateral movement do you have? The tolerance under gravity loads only is typically "ZERO"! Is there differential settlement? How long has this been going on? Have you set up any form of monitoring? Is there any evidence of distress? If there is differential settlement, the frame of the building might be undergoing more displacement than designed.....>>>>higher stresses. What type of building frame is it?

 

[msquared48]

Sounds like the Leaning Tower of Pizza - and foundation problems.

Mike McCann
MMC Engineering

 

[msquared48]

Could be movement induced by vibration too. Any construction or boaring projects nearby?

Mike McCann
MMC Engineering

 

[chekre]

Guys please calm down. the building that i have has a triangular shape with core wall at one of the 3 sides. at ground floor, some columns are being transfered through thick drop beams. the foundation is modeled as a fixity so no foundation problem. i Have joined as attachement a typical floor layout. It is 12 story and the max diplacement is coming around 8cm.

 

[chekre]

the 3D model is done using Etabs and after running the analysis, i noticed that the building was moving laterally probably to the torsion which is the 1st mode here.

 

[BAretired]

So it isn't a real building picking up its skirts and walking off the site?

BA

 

[Ron]

BAretired...

Chekre....Have you considered that the heterogeneous nature of your model might be introducing errors?

 

[msquared48]

Oh... So this is the leaning tower of Etabs...

Mike McCann
MMC Engineering

 

[ahmedhegazi]

I guess problem is in your transfer level , provide supports there and see is your building still move or no

 

[chekre]

Ron The model is ok and no errors. I rechecked it. Any ideas or suggestions ?
Thanks

 

[Guest262653]

What you have is differential shortening of the columns and shear walls due to the difference stresses in these elements. This effect induces a lateral displacement on your structure because the core walls are eccentric. The displacements you get on the model are unrealistic as a significant part of the elastic portion of the vertical displacement is compensated in each floor construction.
What you might do the eliminate this issue is a) include the construction sequence in the model or b) increase the axial stiffness of the columns in order to get the same vertical displacements in the walls and in the columns (beware of the side-effects associated to the change of the global lateral stiffness).

Hope it helps