Buoyancy Imposed at Elevator Pit
Buoyancy Imposed at Elevator Pit
(OP)
The site has excess water.
After completion of construction, there will be two feet of water above the bottom elevation of the elevator pad footing.
I need to perform a bouyancy calculation to determine the required gravity dead load to resist the upward bouyancy force imposed at the bottom of the elevator pad footing.
What is(are) the calculation(s)?
Any other helpful comments or suggestions?
Thank you in advance!
After completion of construction, there will be two feet of water above the bottom elevation of the elevator pad footing.
I need to perform a bouyancy calculation to determine the required gravity dead load to resist the upward bouyancy force imposed at the bottom of the elevator pad footing.
What is(are) the calculation(s)?
Any other helpful comments or suggestions?
Thank you in advance!






RE: Buoyancy Imposed at Elevator Pit
In my experience, the only case where this force has been an issue is with underground storage tanks. When the tanks are empty, the buoyancy force is much higher than the weight of the tanks and they must be anchored to a concrete footing.
Anyway, you can check your structure and see. Good luck.
RE: Buoyancy Imposed at Elevator Pit
RE: Buoyancy Imposed at Elevator Pit
RE: Buoyancy Imposed at Elevator Pit
Before starting of analysis/design you should have the following data -
1) Size of Tank/Pit.
2) Depth of Tank/Pit below G.L.
3) High Flood Level/Maximum Ground Water Table (Worst for 50/100 years)
While Analysis/design you have to consider the following load cases -
1) Full Water/Liquid inside & no earth/GWT/Surcharge outside.
2) No Water inside the tank/pit & Full Earth/Ground Water Table/Surcharge outside.
While designing the base slab/wall you have to design it as a uncracked section for the moments/forces developed due to above load cases.
Base slab should be designed as a uncracked section for the moments developed due to upward pressure of GWT.
The Dead weight required to resist the uplift forces developed due to ground water table should be 20% more than the uplift pressure. (As per clause 4.2.b pp-7 of IS-3370(part-I), 1965.)
I hope this will give you a very brief idea. If you need any help, send email
Paresh
RE: Buoyancy Imposed at Elevator Pit
RE: Buoyancy Imposed at Elevator Pit
RE: Buoyancy Imposed at Elevator Pit