Jack up the centre of the trusses then reinforce each bottom chord with a 2x4 that spans the entire width of the garage.
How to reinforce roof trusses.
Use wood adhesive underneath the sheathing along the connecting joint with the roof trusses.
The central w shape is how most of the loads are distributed and this is where.
To reinforce the ends of the trusses 3 4 inch plywood gussets were to be attached to both sides of each truss with 10d nails 3 inches on center on all chords.
Usually trusses are put 24 inches apart.
Apply construction adhesive along the edge of the truss to strengthen the connection to the plywood roof deck.
To hold them up until the decking of the roof is placed on top a 12 foot 1 inch by 4 inch piece of lumber is used.
Each side of the iron should be four inches wide with the entire piece being at least two feet long.
Jack up the centre reinforce as above and also replace any wood strapping with steel mending plates hurricane ties etc leave it as is strap up drywall pray to the gods.
They work through a combination of tension and compression to ensure that the timber chords and web sizes can be kept to a minimum and keep costs down.
Attach gusset plates at each connection site to fasten the finished truss.
Space them four inches apart along the edges and six inches apart in the middle of the plywood sheathing.
To keep the plywood from cupping under the load 2x4 squash blocks were to be inserted between the top and bottom chords.
Apply a thin layer of construction adhesive to the backside of a plate.
Connect roof sheathing to the roof framing with ten penny weight common or eight penny weight ring shank nails.
Then flip it over and press it firmly into place over a joint between two truss beams.
This will give some added strength and take care of any cracks in the wood itself.
It can be nailed temporarily to each truss as the next truss is put in place.
When all the trusses are installed and the first row of decking is on this brace is removed.