Stirrups for one-way shear in two-way slabs

[Rsd789]

With the shear capacity change in 318-19 I imagine shear reinforcement has become a lot more common for transfer slabs however I think it's unclear which spacing requirements should be used. Have other engineers been using the two-way slab spacing requirements indicated in Table 8.7.6.3 or beam requirements in table 9.7.6.2.2?

8.7.6 is titled "shear reinforcement - stirrups" and doesn't specify that it's only applicable to two-way shear but the remaining subsection imply that it is. Meanwhile, the one-way slab requirements of 7.7.5 simply refer to the beam requirements which is why I could make the argument for those requirements as well.

 

[jayrod12]

How would stirrups work for a one way shear? are you envisioning a single legged stirrup with 180 degree hooks at some spacing in each direction? Certainly just increasing the slab thickness is more cost effective than tying all that reinforcing.

 

[Rsd789]

I was initially thinking either multiple-leg stirrup bars or closed stirrups depending on how many legs would be required based on the spacing. If the shear failures occur throughout the slab I would agree but for transfer slabs it's common for only a few locations too be failing, in which case I don't think increasing the total thickness would be cost effective

 

[bones206]

I could envision single leg ties distributed uniformly within high shear zones, then omitted for the remainder of the slab where it’s not required. Similar concept as stud rails.

 

[cliff234]

I suggest using “studrail” type shear reinforcing. This reinforcing is much easier and faster to install than loose single leg stirrups.

 

[Rsd789]

I think stud rails would certainly be easier however it's not listed as a permitted form of one-way shear reinforcement per 22.5.8.5.1. Very unusual as it can be used for two-way shear and I believe other codes allow the use for one-way shear. Might require some "engineering judgement" to justify them working but certainly a possible solution