[jivetyrant]

So I have a beefy (12.2%) Tripel in bottles right now, it's been sitting for about 2 1/2 weeks.  I cracked one last night and it was practically flat, yikes!  I forgot to add some fresh yeast at bottling time and don't have a kegging system yet, but I've read of people cracking the caps on the whole batch and adding a sprinkle of dry yeast to each bottle then capping them all again.  Would a standard dry yeast like US-05 work for this purpose?  Can I simply sprinkle it in dry or should i rehydrate it first?  Are there any other alternatives?  Thanks!

[bluesman]

Residual yeast in suspension, available fermentable sugar, time and temperature are the four factors to consider upon bottle carbonation. What temp are the bottles sitting at right now? Try warming them up to about 70 degrees. I usually condition my bottles in the warmest room of my house for a few weeks during bottle carbonation.

[tygo]

Since you didn't add fresh yeast at bottling time you may want to try popping them open and sprinkling in some dried yeast. 

However, before you try that I would wait awhile longer.  Warm them up like Bluesman said and give it another month or so and see if the carbonation level changes.  I've found that with beers that strong it can take a lot longer to carb up when bottle conditioning.   

[liquidbrewing]

That high of ABV, your yeast is stressed.  Either add more yeast to each bottle, like you're suggesting, or wait longer.  I brewed a batch of barleywine last Dec.  12%, added yeast when I bottled, cracked one open three weeks into bottle conditioning, perfect carbonation.

And yes, US-05 would be perfect for this.  That's been my go to yeast for a while.  Nice and clean flavor.

[tygo]

12%, added yeast when I bottled, cracked one open three weeks into bottle conditioning, perfect carbonation.

My experience with that is that after I cracked a bottle three weeks into bottle conditioning I was pissed because it was close to flat.  After another month or so though the carbonation level did come up to what I was expecting.  Each beer is different.  Waiting a little longer is probably the best course of action at this point. 

[jivetyrant]

Excellent   I'll give it another two weeks and try again.  They're currently in towel lined rubbermaid containers in the warmest room of the house, my min/max thermometer shows max of 71, min of 66.