"Dan Oelke" wrote
In my current abode they used floor trusses for both the first and second
floor. From the basement I have easy access (for now) to the first floor
trusses. They are great in that they allow for such a long span and a
very open floor plan. However - there is a fair amount of bounce in the
floors, especially when two kids get a little excited running around the
house. This is especially true in the kitchen area which has cabinets all
around, heavy appliances, island, etc. so I suspect that this added
"normal" load makes them a little more flexible.

Does anyone have any suggestions for how to stiffen or strengthen these
trusses?

Sister a 2" x 12" on each side of each floor truss.
Then nail 2 x 12 blocking perpendicular between the trusses at 48" o/c.
This is the expensive way, but the floor will be like concrete when you're
done.