one way or two way slabs

[civil78]

Does anyone know of any basic rules that define one way from two way slabs? It looks like the test would identify which type was needed (at least for the AM portion), but I didn't know if there was anything solid that would be a definite differentiation.

Thanks-

 

[MA_PE]

The designer is the one that decides whether he wants to design the slab as a one-way slab or if he wants to consider two-way action. Obviously the slab needs support on all for edges before one can consider two-action. Slabs supported only on two opposite edges are by defintion one-way slabs. Hope that helps.

 

[YJ_Civil_PE]

ACI 318 R13.6.1.2 says, "If the ratio of the two spans (long span/short span) of a panel exceeds two, the slab resists the moment in the shorter span essentially as a one-way slab."

R9.5.3.3 also states that using the equations for minimum thickness of two-way slab (9-12) and (9-13) "may give unreasonable results" for panels with a ratio of long to short span greater than 2.

So, there you have it!