One Way/Two Way Slab Systems

[gmannix2012]

Hi guys,

Have this scenario whereby two one way slabs are intersecting. The overlapping (rectangular) slab is not supported on two sides like the one way slabs are by walls below. There is a wall running along beneath one edge of it and the other two opposite corners can be deemed as being fixed; these are the support conditions.

Therefore, it is more of a two way system.

What's the best way to design this (as quickly as possible)... I'm using CSA A23.3 also.

 

[frv]

Post a sketch so you can get better feedback.

 

[dik]

I'd probably treat it as a propped cantilever in two directions with total fixity at the re-entrant corner. I'd use a few heavy bars (maybe 25M; these can be your beam top steel) at the re-entrant corner and make up the balance with lighter bars (maybe 15M or 20M)... and carry the lighter top reinforcing as dowels into the beam.

A sketch would help to confirm my comments...

Dik

 

[rapt]

You need to look at where the loads are going to. If the one way slabs are depositing their loads on another area of slab, rather than a support, then you need a strong band to carry that load to the supports. That is really all a 2 way slab is, with the column strips providing the strong bands.

The difference with a 2way slab is that it is happening in 2 directions at once, so you end up with a variatioon in the moment in the stronger column strips between -ve and +ve moment areas. If all of your supports are walls in this case, then you need a strong band to carry the slab load to the supports. This band will carry itself plus the extra load dropped onto it.