Basement wall with reduced bracing slab.

[chekre]

Good day,

In a recent project, i had to deal with a typical basement wall extending 4 stories below ground.
The basement slabs were designed as a 300mm thick post tensioned plate.
The basement walls were designed in a separate model assuming pinned connection at the level of the slab.
Here comes the problem.
I just got a call from the contractor that he will not be able to proceed with the post tensioning for the slabs under ground.
He is proposing a hollow core one way slab with a topping of 70mm above it.
I dont believe that this 70mm will act properly as a bracing element for the basement wall

Cast in situ option is not feasible due to the large spans (9m and above).
I am looking for some suggestions.
Thank you.

 

[KootK]

With suitable connection details, I'd be fine with using the precast floor plate to brace the the basement walls. Nothing ever feels as good as monolithic cast in place concrete but other systems have proven themselves adequate.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[chekre]

Thank you.

 

[KootK]

You're welcome. For what it's worth, I've renovated a number of buildings in my area from the 70's that use a similar system. The precast has deteriorated but the basement walls seem to be doing fine. With these build, the topping is asphalt which is even more questionable from a diaphragm standpoint.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.