looking to increase ceiling heigh in this area of customers grage for a car lift. Looking to add load bearing wall (new footings) interior to support the bottom chord and remove the offending portion of the cord. Thoughts?
1) You're going to create stress reversals in several of the truss webs adjacent to the new bearing wall. So you'll need to tend to that with respect to the webs and, potentially, the plated joints there.
2) I was once a truss designer myself and I'd be willing to do this FWIW. I feel that it's a fairly robust and well thought out solution.
My first thought was gross, but the more I looked at it, the more I didn't mind the idea.
My one comment regarding koot's second post point 1, make sure that it works for the unbraced length since that chord won't be sheathed. Or plan to sheath/brace that chord on each truss to get the required resistance.
The top chord extension to the exterior wall will have enough strength and stiffness to brace the exterior wall, and the bottom chord would still have its continuity from the new wall onwards.
I have a similar project but I ended up getting rid the trusses along the lift instead. I added a beam and king post on each side and added a ridge beam in between. I then added new rafters (supported by the new ridge beam) that I sister to existing top chord. So essentially now we have vaulted ceiling along this ridge beam.
Put a vertical in over the wall to close out the truss. Need to design it and get the connections right and also check the existing top hors spinning as a rafter over the carport.