Expansion joint in basement? 1

[iyota]

Hello friends,

We're designing a building about 100ft x 330ft long, with 4 basement floors.

An expansion joint is provided from ground level to the roof.

However, I feel that we should NOT put an expansion joint in the basement box. This is because it is about 30ft underwater and in reclaimed sand. So it's practically under the sea. A flexible joint could be a big problem. Besides, basements are subject to less temperature change.


But I have doubts if this is ok (no exp joint in basement)

Any opinions? What do you think?

Thank you in advance!

 

[rowingengineer]

What type of basement construction are we talking about, bottom up backfilled, bottom up cantilevered, bottom up temporary staged, top down or a hybrid.
Movement joints are rarely required below ground level; however the advice on how to control cracking of the slab is reliant on the question above. I prefer the bottom up cantilevered type construction, with secant piles, maybe a tie back. For this type of construction I would place pour strips/construction at the edges and centres along the building, leaving these for as long as I can before concreting the pour strips. Your water proofing level is also important; I always like to have this signed off by the client, before starting the selection process.

Nevertheless if you are going to have movement joints above ground just remember you do need to account for this in your detailing of columns and walls before you get to ground level. This would be very important if you have a tower to podium level.


An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[iyota]

Thanks for replying rowingengineer,

Basement construction will be bottom-up, with a diaphragm wall tied to temporary ground anchors.

And yes, there will a delayed-pour strip all around the perimeter wall for the slab to shrink at curing.

Correct, the waterproofing has been my biggest concern for the basement, hence I'd like to have no expansion joint in the basement if it's possible. Construction joints we can't avoid, but expansion joints none if possible.

 

[hokie66]

I would avoid movement joints in the floors below ground, especially in the bottom slab which has to resist hydrostatic uplift. I think this slab should have an underslab membrane, and be designed with at least .6% reinforcement for crack control. The other basement floors are required to serve as diaphragms to distribute the earth pressure, so unless there are internal shear walls, these have to be continuous as well.