A very thin RC flat plate. 2

[Huck85]

How can this RC slab be very thin? It seems photoshoped.

 

[IDS]

The visible edge of the near cantilever is very thin, but the top surface isn't flat - see left hand edge.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Ingenuity]

Looks like Lift Slab (and possibly post-tensioned) - common during the 60's through 80's in the US until L'Ambiance Plaza collapse (during construction) in 1987.

 

[HTURKAK]

I agree with Ingenuity .Aparently, the columns in the picture are steel. The lift slab method was novel technology of 70's.

https://www.youtube.com/watch?v=BcXQsnnaA00

https://www.youtube.com/results?search_query=lift+slab+system

 

[Ingenuity]

It appears the OP's photograph is from Trinity University in San Antonio, TX dated in 1952. So Likely it is RC only and NOT post-tensioned.

Here is another view of the structure. Note edge taper and step, as IDS noted.

 

[Ingenuity]

Fun fact about Lift-Slab and Trinity University:

The method was first used at Trinity University in San Antonio, Texas during the construction of Northup Hall in 1952. Northrup Hall was the first full scale building erected using lift slab construction. Being such, the process drew a crowd of spectators, waiting to see if the structural integrity of the building would hold.