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Tilt-up connections

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    ACI-318 05 has revised the precast seismic connection requirements.  The new concepts on the surface appear to be well considered.  However, some local firms have taken an interesting twist on them.  I generally anchor tilt panels to the footing for a 10 kip minimum per the precast chapter, regardless of the demand.  Now under the new provisions we will also make that connection meet the new ductility provisions in chapter 21.  We were doing this before with a slightly different philosophy, but it appears to get very close to the same results. 

    A competing local engineer pointed out that the PCA Notes to 318 05 state the ductility provisions and minimum connections don't apply to tilts.  SEAOC and some letters to Stuctures Magazine feel anchoring to the slab only is a bad idea in high seismic zones (say seismic design category C+).  Some local firms will do an overturning calculation with an R of 5, determine there is no net uplift, and only anchor to the slab.  How does PCA justify that statement and is there any rational reason in ACI 318 to support it?

Jake Watson, P.E.
Salt Lake City, UT