I just had bottom bracket replaced and new chain on my road bike.

I put my bike on the trainer and found when in the middle of triple front chainring, I get a grinding noise, seems to be mostly at the point of contact of chain and ring.
I do not get noise on the small or larger ring, nor any ring with no load.

I have a 10spd Shimano 105 set and never geard this before.

Thanks for any info.

Check Sheldon Brown's guide to interpreting bicycle noises.

If you're not sure which area the noise is coming from, report back when you've identified it as a chain (noise once per chain cycle), BB/chainrings/FD (noise once or twice per pedal stroke), RD/cassette/wheel (noise at same wheel position(s)), etc. I encourage you to follow his noise-finding procedures because noises often come from strange places and transmit themselves along the frame.

However, from your description, it sounds like you're confident that it's a regular-with-pedal-stroke problem. Make sure indexing is set properly, and that the FD is centred over the middle chainring when you're shifted to that position. Check to see if it looks like the middle chainring rubs the FD when you pedal hard, in which case you might need to re-tighten the chainring bolts and make sure they are straight. This could also indicate a loose BB, which could grind (but will usually click or creak) under load. If the BB is loose, you should be able to produce creaks by pulling the crank HARD towards the frame. Also, examine the middle chainring for weird imperfections or excessive wear (you probably use it often), and check your chain for wear.

Of course, you can probably rule many of these possibilities out immediately, because you have seen the bike and the rest of us have not.

Chain and rear cogs can wear down together especially when the chain was really worn out. The "streched" chain wears the cogs more, and so the new chain makes a grinding. It can make the grinding noises more on the middle front ring than on the large ring. Since you just finished replacing the bb and chain both I'm betting it was pretty worn out. Odds are you need to change the cassette. Less likely, the chainring.

That's more likely than anything I suggested. What sort of mileage did you have on the old chain and the current cassette and chainrings?

Thanks
I had about 2000 on last chain, and it just reached its stretch limit before I changed it.
The chain ring has about 12,000 miles on it. The rear Cassette has about 4000 miles on it
The middle fronnt chain ring does feel a little worn, but I guess even some wear into to he old chain, will make a new chain sound funny. I will look at the Sheldon Brown info noted.

Thanks

If the grinding occurs only when you are on the middle ring, this points to the middle ring being worn (look for "hooked" teeth), and it is especially likely with a new chain. The old worn chain probably mated fine with the worn ring. I suspect that the middle ring was most used and got the most wear, which is why it's "protesting" the new chain while the inner and outer rings are not giving you problems. Replace the middle ring and the problem should resolve. BTW, your rear sprockets are probably worn too, but not so much that they don't "cooperate" with your new chain...yet.
You might need to replace the rear hub gears.